server.js

'use strict';

if (!process.env.EE_ENV_LOADED) {
    require('dotenv').config(); // eslint-disable-line global-require
    process.env.EE_ENV_LOADED = 'true';
}

try {
    process.chdir(__dirname);
} catch (err) {
    // ignore
}

process.title = 'emailengine';

try {
    structuredClone(true);
} catch (err) {
    console.error(`Please upgrade your Node.js version as the current version (${process.version}) is not supported.`);
    process.exit(1);
}

const os = require('os');
process.env.UV_THREADPOOL_SIZE =
    process.env.UV_THREADPOOL_SIZE && !isNaN(process.env.UV_THREADPOOL_SIZE) ? Number(process.env.UV_THREADPOOL_SIZE) : Math.max(os.cpus().length, 4);

// cache before wild-config
const argv = process.argv.slice(2);

const { Worker, SHARE_ENV } = require('worker_threads');
const packageData = require('./package.json');
const config = require('wild-config');
const logger = require('./lib/logger');

const {
    readEnvValue,
    hasEnvValue,
    download,
    getDuration,
    getByteSize,
    getBoolean,
    getWorkerCount,
    selectRendezvousNode,
    checkLicense,
    checkForUpgrade,
    setLicense,
    getRedisStats,
    threadStats
} = require('./lib/tools');

const {
    MAX_DAYS_STATS,
    MESSAGE_NEW_NOTIFY,
    MESSAGE_DELETED_NOTIFY,
    CONNECT_ERROR_NOTIFY,
    REDIS_PREFIX,
    ACCOUNT_ADDED_NOTIFY,
    ACCOUNT_DELETED_NOTIFY,
    LIST_UNSUBSCRIBE_NOTIFY,
    LIST_SUBSCRIBE_NOTIFY,
    FETCH_TIMEOUT
} = require('./lib/consts');

const { webhooks: Webhooks } = require('./lib/webhooks');
const {
    generateSummary,
    generateEmbeddings,
    getChunkEmbeddings,
    embeddingsQuery,
    questionQuery,
    listModels: openAiListModels,
    DEFAULT_USER_PROMPT: openAiDefaultPrompt
} = require('@postalsys/email-ai-tools');
const { fetch: fetchCmd, Agent } = require('undici');
const fetchAgent = new Agent({ connect: { timeout: FETCH_TIMEOUT } });

const v8 = require('node:v8');

const Bugsnag = require('@bugsnag/js');
if (readEnvValue('BUGSNAG_API_KEY')) {
    Bugsnag.start({
        apiKey: readEnvValue('BUGSNAG_API_KEY'),
        appVersion: packageData.version,
        logger: {
            debug(...args) {
                logger.debug({ msg: args.shift(), worker: 'main', source: 'bugsnag', args: args.length ? args : undefined });
            },
            info(...args) {
                logger.debug({ msg: args.shift(), worker: 'main', source: 'bugsnag', args: args.length ? args : undefined });
            },
            warn(...args) {
                logger.warn({ msg: args.shift(), worker: 'main', source: 'bugsnag', args: args.length ? args : undefined });
            },
            error(...args) {
                logger.error({ msg: args.shift(), worker: 'main', source: 'bugsnag', args: args.length ? args : undefined });
            }
        }
    });
    logger.notifyError = Bugsnag.notify.bind(Bugsnag);
}

const pathlib = require('path');
const { redis, queueConf } = require('./lib/db');
const promClient = require('prom-client');
const fs = require('fs').promises;
const crypto = require('crypto');
const { compare: cv } = require('compare-versions');
const Joi = require('joi');
const { settingsSchema } = require('./lib/schemas');
const settings = require('./lib/settings');
const tokens = require('./lib/tokens');

const { checkRateLimit } = require('./lib/rate-limit');

const { QueueEvents } = require('bullmq');

const getSecret = require('./lib/get-secret');

const msgpack = require('msgpack5')();

config.service = config.service || {};

config.workers = config.workers || {
    imap: 4,
    webhooks: 1,
    submit: 1,
    imapProxy: 1
};

config.dbs = config.dbs || {
    redis: 'redis://127.0.0.1:6379/8'
};

config.log = config.log || {
    level: 'trace'
};

config.api = config.api || {
    port: 3000,
    host: '127.0.0.1'
};

config.smtp = config.smtp || {
    enabled: false,
    port: 2525,
    host: '127.0.0.1',
    secret: '',
    proxy: false
};

config['imap-proxy'] = config['imap-proxy'] || {
    enabled: false,
    port: 2993,
    host: '127.0.0.1',
    secret: '',
    proxy: false
};

const NOW = Date.now(); // time of start

const DEFAULT_EENGINE_TIMEOUT = 10 * 1000;
const EENGINE_TIMEOUT = getDuration(readEnvValue('EENGINE_TIMEOUT') || config.service.commandTimeout) || DEFAULT_EENGINE_TIMEOUT;
const DEFAULT_MAX_ATTACHMENT_SIZE = 5 * 1024 * 1024;
const SUBSCRIPTION_CHECK_TIMEOUT = 1 * 24 * 60 * 60 * 1000;
const SUBSCRIPTION_ALLOW_DELAY = 28 * 24 * 60 * 60 * 1000;

const CONNECTION_SETUP_DELAY = getDuration(readEnvValue('EENGINE_CONNECTION_SETUP_DELAY') || config.service.setupDelay) || 0;

config.api.maxSize = getByteSize(readEnvValue('EENGINE_MAX_SIZE') || config.api.maxSize) || DEFAULT_MAX_ATTACHMENT_SIZE;
config.dbs.redis = readEnvValue('EENGINE_REDIS') || readEnvValue('REDIS_URL') || config.dbs.redis;

config.workers.imap = getWorkerCount(readEnvValue('EENGINE_WORKERS') || config.workers.imap) || 4;

config.workers.webhooks = Number(readEnvValue('EENGINE_WORKERS_WEBHOOKS')) || config.workers.webhooks || 1;
config.workers.submit = Number(readEnvValue('EENGINE_WORKERS_SUBMIT')) || config.workers.submit || 1;

config.api.port =
    (hasEnvValue('EENGINE_PORT') && Number(readEnvValue('EENGINE_PORT'))) || (hasEnvValue('PORT') && Number(readEnvValue('PORT'))) || config.api.port;
config.api.host = readEnvValue('EENGINE_HOST') || config.api.host;

config.log.level = readEnvValue('EENGINE_LOG_LEVEL') || config.log.level;

// legacy options, will be removed in the future
const SMTP_ENABLED = hasEnvValue('EENGINE_SMTP_ENABLED') ? getBoolean(readEnvValue('EENGINE_SMTP_ENABLED')) : getBoolean(config.smtp.enabled);
const SMTP_SECRET = readEnvValue('EENGINE_SMTP_SECRET') || config.smtp.secret;
const SMTP_PORT = (readEnvValue('EENGINE_SMTP_PORT') && Number(readEnvValue('EENGINE_SMTP_PORT'))) || Number(config.smtp.port) || 2525;
const SMTP_HOST = readEnvValue('EENGINE_SMTP_HOST') || config.smtp.host || '127.0.0.1';
const SMTP_PROXY = hasEnvValue('EENGINE_SMTP_PROXY') ? getBoolean(readEnvValue('EENGINE_SMTP_PROXY')) : getBoolean(config.smtp.proxy);

const IMAP_PROXY_ENABLED = hasEnvValue('EENGINE_IMAP_PROXY_ENABLED')
    ? getBoolean(readEnvValue('EENGINE_IMAP_PROXY_ENABLED'))
    : getBoolean(config['imap-proxy'].enabled);
const IMAP_PROXY_SECRET = readEnvValue('EENGINE_IMAP_PROXY_SECRET') || config['imap-proxy'].secret;
const IMAP_PROXY_PORT =
    (readEnvValue('EENGINE_IMAP_PROXY_PORT') && Number(readEnvValue('EENGINE_IMAP_PROXY_PORT'))) || Number(config['imap-proxy'].port) || 2993;
const IMAP_PROXY_HOST = readEnvValue('EENGINE_IMAP_PROXY_HOST') || config['imap-proxy'].host || '127.0.0.1';
const IMAP_PROXY_PROXY = hasEnvValue('EENGINE_IMAP_PROXY_PROXY')
    ? getBoolean(readEnvValue('EENGINE_IMAP_PROXY_PROXY'))
    : getBoolean(config['imap-proxy'].proxy);

const HAS_API_PROXY_SET = hasEnvValue('EENGINE_API_PROXY') || typeof config.api.proxy !== 'undefined';
const API_PROXY = hasEnvValue('EENGINE_API_PROXY') ? getBoolean(readEnvValue('EENGINE_API_PROXY')) : getBoolean(config.api.proxy);

logger.info({
    msg: 'Starting EmailEngine',
    version: packageData.version,
    node: process.versions.node,
    uvThreadpoolSize: Number(process.env.UV_THREADPOOL_SIZE),
    workersImap: config.workers.imap,
    workersWebhooks: config.workers.webhooks,
    workersSubmission: config.workers.submit
});

const NO_ACTIVE_HANDLER_RESP = {
    error: 'No active handler for requested account. Try again later.',
    statusCode: 503,
    code: 'WorkerNotAvailable'
};

// check for upgrades once in 8 hours
const UPGRADE_CHECK_TIMEOUT = 1 * 24 * 3600 * 1000;
const LICENSE_CHECK_TIMEOUT = 20 * 60 * 1000;
const MAX_LICENSE_CHECK_DELAY = 30 * 24 * 60 * 60 * 1000;

const licenseInfo = {
    active: false,
    details: false,
    type: packageData.license
};

const THREAD_NAMES = {
    main: 'Main thread',
    imap: 'IMAP worker',
    webhooks: 'Webhook worker',
    api: 'HTTP and API server',
    submit: 'Email sending worker',
    documents: 'Document store indexing worker',
    imapProxy: 'IMAP proxy server',
    smtp: 'SMTP proxy server'
};

const THREAD_CONFIG_VALUES = {
    imap: { key: 'EENGINE_WORKERS', value: config.workers.imap },
    submit: { key: 'EENGINE_WORKERS_SUBMIT', value: config.workers.submit },
    webhooks: { key: 'EENGINE_WORKERS_WEBHOOKS', value: config.workers.webhooks }
};

const queueEvents = {};

let runIndex;

let preparedSettings = false;
const preparedSettingsString = readEnvValue('EENGINE_SETTINGS') || config.settings;
if (preparedSettingsString) {
    // received a configuration block
    try {
        const { error, value } = Joi.object(settingsSchema).validate(JSON.parse(preparedSettingsString), {
            abortEarly: false,
            stripUnknown: true,
            convert: true
        });

        if (error) {
            throw error;
        }

        preparedSettings = value;
    } catch (err) {
        logger.error({ msg: 'Received invalid settings string', input: preparedSettingsString, err });
        logger.flush(() => process.exit(1));
    }
}

let preparedToken = false;
const preparedTokenString = readEnvValue('EENGINE_PREPARED_TOKEN') || config.preparedToken;
if (preparedTokenString) {
    try {
        preparedToken = msgpack.decode(Buffer.from(preparedTokenString, 'base64url'));
        if (!preparedToken || !/^[0-9a-f]{64}$/i.test(preparedToken.id)) {
            throw new Error('Invalid token format');
        }
    } catch (err) {
        logger.error({ msg: 'Received invalid token string', input: preparedTokenString, err });
        logger.flush(() => process.exit(1));
    }
}

let preparedPassword = false;
const preparedPasswordString = readEnvValue('EENGINE_PREPARED_PASSWORD') || config.preparedPassword;
if (preparedPasswordString) {
    try {
        preparedPassword = Buffer.from(preparedPasswordString, 'base64url').toString();
        if (!preparedPassword || preparedPassword.indexOf('$pbkdf2') !== 0) {
            throw new Error('Invalid password format');
        }
    } catch (err) {
        logger.error({ msg: 'Received invalid password string', input: preparedPasswordString, err });
        logger.flush(() => process.exit(1));
    }
}

const collectDefaultMetrics = promClient.collectDefaultMetrics;
collectDefaultMetrics({});

const metrics = {
    threadStarts: new promClient.Counter({
        name: 'thread_starts',
        help: 'Number of started threads'
    }),

    threadStops: new promClient.Counter({
        name: 'thread_stops',
        help: 'Number of stopped threads'
    }),

    apiCall: new promClient.Counter({
        name: 'api_call',
        help: 'Number of API calls',
        labelNames: ['method', 'statusCode', 'route']
    }),

    imapConnections: new promClient.Gauge({
        name: 'imap_connections',
        help: 'Current IMAP connection state',
        labelNames: ['status']
    }),

    imapResponses: new promClient.Counter({
        name: 'imap_responses',
        help: 'IMAP responses',
        labelNames: ['response', 'code']
    }),

    imapBytesSent: new promClient.Counter({
        name: 'imap_bytes_sent',
        help: 'IMAP bytes sent'
    }),

    imapBytesReceived: new promClient.Counter({
        name: 'imap_bytes_received',
        help: 'IMAP bytes received'
    }),

    webhooks: new promClient.Counter({
        name: 'webhooks',
        help: 'Webhooks sent',
        labelNames: ['status', 'event']
    }),

    events: new promClient.Counter({
        name: 'events',
        help: 'Events fired',
        labelNames: ['event']
    }),

    webhookReq: new promClient.Histogram({
        name: 'webhook_req',
        help: 'Duration of webhook requests',
        buckets: [100, 250, 500, 750, 1000, 2500, 5000, 7500, 10000, 60 * 1000]
    }),

    queues: new promClient.Gauge({
        name: 'queue_size',
        help: 'Queue size',
        labelNames: ['queue', 'state']
    }),

    queuesProcessed: new promClient.Counter({
        name: 'queues_processed',
        help: 'Processed job count',
        labelNames: ['queue', 'status']
    }),

    emailengineConfig: new promClient.Gauge({
        name: 'emailengine_config',
        help: 'Configuration values',
        labelNames: ['version', 'config']
    }),

    redisVersion: new promClient.Gauge({
        name: 'redis_version',
        help: 'Redis version',
        labelNames: ['version']
    }),

    redisUptimeInSeconds: new promClient.Gauge({
        name: 'redis_uptime_in_seconds',
        help: 'Redis uptime in seconds'
    }),

    redisPing: new promClient.Gauge({
        name: 'redis_latency',
        help: 'Redis latency in nanoseconds'
    }),

    redisRejectedConnectionsTotal: new promClient.Gauge({
        name: 'redis_rejected_connections_total',
        help: 'Number of connections rejected by Redis'
    }),

    redisConfigMaxclients: new promClient.Gauge({
        name: 'redis_config_maxclients',
        help: 'Maximum client number for Redis'
    }),

    redisConnectedClients: new promClient.Gauge({
        name: 'redis_connected_clients',
        help: 'Number of client connections for Redis'
    }),

    redisSlowlogLength: new promClient.Gauge({
        name: 'redis_slowlog_length',
        help: 'Number of of entries in the Redis slow log'
    }),

    redisCommandsDurationSecondsTotal: new promClient.Gauge({
        name: 'redis_commands_duration_seconds_total',
        help: 'How many seconds spend on processing Redis commands'
    }),

    redisCommandsProcessedTotal: new promClient.Gauge({
        name: 'redis_commands_processed_total',
        help: 'How many commands processed by Redis'
    }),

    redisKeyspaceHitsTotal: new promClient.Gauge({
        name: 'redis_keyspace_hits_total',
        help: 'Number of successful lookup of keys in Redis'
    }),

    redisKeyspaceMissesTotal: new promClient.Gauge({
        name: 'redis_keyspace_misses_total',
        help: 'Number of failed lookup of keys in Redis'
    }),

    redisEvictedKeysTotal: new promClient.Gauge({
        name: 'redis_evicted_keys_total',
        help: 'Number of evicted keys due to maxmemory limit in Redis'
    }),

    redisMemoryUsedBytes: new promClient.Gauge({
        name: 'redis_memory_used_bytes',
        help: 'Total number of bytes allocated by Redis using its allocator'
    }),

    redisMemoryMaxBytes: new promClient.Gauge({
        name: 'redis_memory_max_bytes',
        help: 'The value of the Redis maxmemory configuration directive'
    }),

    redisMemFragmentationRatio: new promClient.Gauge({
        name: 'redis_mem_fragmentation_ratio',
        help: 'Ratio between used_memory_rss and used_memory in Redis'
    }),

    redisKeyCount: new promClient.Gauge({
        name: 'redis_key_count',
        help: 'Redis key counts',
        labelNames: ['db']
    }),

    redisLastSaveTime: new promClient.Gauge({
        name: 'redis_last_save_time',
        help: 'Unix timestamp of the last RDB save time'
    }),

    redisOpsPerSec: new promClient.Gauge({
        name: 'redis_instantaneous_ops_per_sec',
        help: 'Throughput operations per second'
    }),

    redisCommandRuns: new promClient.Gauge({
        name: 'redis_command_runs',
        help: 'Redis command counts',
        labelNames: ['command']
    }),

    redisCommandRunsFailed: new promClient.Gauge({
        name: 'redis_command_runs_fail',
        help: 'Redis command counts',
        labelNames: ['command', 'status']
    })
};

let callQueue = new Map();
let mids = 0;

let isClosing = false;
let assigning = false;

let unassigned = false;
let assigned = new Map();
let unassignCounter = new Map();
let workerAssigned = new WeakMap();
let onlineWorkers = new WeakSet();

let imapInitialWorkersLoaded = false;
let workers = new Map();
let workersMeta = new WeakMap();
let availableIMAPWorkers = new Set();

let suspendedWorkerTypes = new Set();

const postMessage = (worker, payload, ignoreOffline, transferList) => {
    if (!onlineWorkers.has(worker)) {
        if (ignoreOffline) {
            return false;
        }
        throw new Error('Requested worker thread not available');
    }

    let result = worker.postMessage(payload, transferList);

    let workerMeta = workersMeta.has(worker) ? workersMeta.get(worker) : {};
    workerMeta.called = workerMeta.called ? ++workerMeta.called : 1;
    workersMeta.set(worker, workerMeta);

    return result;
};

const countUnassignment = async account => {
    if (!unassignCounter.has(account)) {
        unassignCounter.set(account, []);
    }
    let arr = unassignCounter.get(account);
    arr.push(Date.now());

    if (arr.length > 10) {
        arr = arr.slice(-10);
        unassignCounter.set(account, arr);
    }

    let delay = 0;
    if (arr.length === 1) {
        delay = 0;
    } else {
        let lastDelay = arr[arr.length - 1] - arr[arr.length - 2];
        // if last delay was longer than a minute, then reset
        if (lastDelay >= 60 * 1000) {
            delay = 0;
        } else {
            delay = Math.min(Math.ceil(lastDelay * 1.5), 60 * 1000);
        }
    }

    await redis.hSetExists(`${REDIS_PREFIX}iad:${account}`, 'state', 'disconnected');

    for (let worker of workers.get('api')) {
        let callPayload = {
            cmd: 'change',
            account,
            type: 'state',
            key: 'disconnected',
            payload: null
        };

        try {
            postMessage(worker, callPayload, true);
        } catch (err) {
            logger.error({ msg: 'Failed to post state change to child', worker: worker.threadId, callPayload, err });
        }
    }

    if (delay) {
        await new Promise(resolve => setTimeout(resolve, delay));
        return true;
    } else {
        return false;
    }
};

let clearUnassignmentCounter = account => {
    unassignCounter.delete(account);
};

let updateServerState = async (type, state, payload) => {
    await redis.hset(`${REDIS_PREFIX}${type}`, 'state', state);
    if (payload) {
        await redis.hset(`${REDIS_PREFIX}${type}`, 'payload', JSON.stringify(payload));
    }

    if (workers.has('api')) {
        for (let worker of workers.get('api')) {
            let callPayload = {
                cmd: 'change',
                type: '${type}ServerState',
                key: state,
                payload: payload || null
            };

            try {
                postMessage(worker, callPayload, true);
            } catch (err) {
                logger.error({ msg: 'Failed to post state change to child', worker: worker.threadId, callPayload, err });
            }
        }
    }
};

async function sendWebhook(account, event, data) {
    let serviceUrl = (await settings.get('serviceUrl')) || null;

    let payload = {
        serviceUrl,
        account,
        date: new Date().toISOString()
    };

    if (event) {
        payload.event = event;
    }

    if (data) {
        payload.data = data;
    }

    await Webhooks.pushToQueue(event, await Webhooks.formatPayload(event, payload));
}

let spawnWorker = async type => {
    if (isClosing) {
        return;
    }

    if (!workers.has(type)) {
        workers.set(type, new Set());
    }

    if (suspendedWorkerTypes.has(type)) {
        if (['smtp', 'imapProxy'].includes(type)) {
            await updateServerState(type, 'suspended', {});
        }
        return;
    }

    if (['smtp', 'imapProxy'].includes(type)) {
        let serverEnabled = await settings.get(`${type}ServerEnabled`);
        if (!serverEnabled) {
            await updateServerState(type, 'disabled', {});
            return;
        }

        await updateServerState(type, 'spawning');
    }

    let worker = new Worker(pathlib.join(__dirname, 'workers', `${type.replace(/[A-Z]/g, c => `-${c.toLowerCase()}`)}.js`), {
        argv,
        env: SHARE_ENV,
        trackUnmanagedFds: true
    });
    metrics.threadStarts.inc();

    workers.get(type).add(worker);

    return new Promise((resolve, reject) => {
        let isOnline = false;
        let threadId = worker.threadId;

        worker.on('online', () => {
            if (['smtp', 'imapProxy'].includes(type)) {
                updateServerState(type, 'initializing').catch(err => logger.error({ msg: `Failed to update ${type} server state`, err }));
            }
            onlineWorkers.add(worker);

            let workerMeta = workersMeta.has(worker) ? workersMeta.get(worker) : {};
            workerMeta.online = Date.now();
            workersMeta.set(worker, workerMeta);

            if (type !== 'imap' && type !== 'api') {
                // IMAP and API workers need to wait until ready to accept accounts
                isOnline = true;
                resolve(threadId);
            }
        });

        let exitHandler = async exitCode => {
            onlineWorkers.delete(worker);
            metrics.threadStops.inc();

            workers.get(type).delete(worker);

            if (['smtp', 'imapProxy'].includes(type)) {
                updateServerState(type, suspendedWorkerTypes.has(type) ? 'suspended' : 'exited');
            }

            if (type === 'imap') {
                availableIMAPWorkers.delete(worker);

                if (workerAssigned.has(worker)) {
                    let accountList = workerAssigned.get(worker);
                    workerAssigned.delete(worker);
                    accountList.forEach(account => {
                        assigned.delete(account);
                        let shouldReassign = false;
                        // graceful reconnect
                        countUnassignment(account)
                            .then(sr => {
                                shouldReassign = sr;
                            })
                            .catch(() => {
                                shouldReassign = true;
                            })
                            .finally(() => {
                                unassigned.add(account);
                                if (shouldReassign) {
                                    assignAccounts().catch(err => logger.error({ msg: 'Failed to assign accounts', n: 1, err }));
                                }
                            });
                    });
                }
            }

            if (isClosing) {
                return;
            }

            // spawning a new worker trigger reassign
            if (suspendedWorkerTypes.has(type)) {
                logger.info({ msg: 'Worker thread closed', exitCode, type });
            } else {
                logger.error({ msg: 'Worker exited', exitCode, type });
            }

            // trigger new spawn
            await new Promise(r => setTimeout(r, 1000));
            await spawnWorker(type);
        };

        worker.on('exit', exitCode => {
            if (!isOnline) {
                let error = new Error(`Failed to start ${type} worker thread on initialization`);

                error.workerType = type;
                error.exitCode = exitCode;
                error.threadId = threadId;

                reject(error);
            }

            exitHandler(exitCode).catch(err => {
                logger.error({ msg: 'Failed to handle worker exit', exitCode, type, worker: worker.threadId, err });
            });
        });

        worker.on('message', message => {
            let workerMeta = workersMeta.has(worker) ? workersMeta.get(worker) : {};
            workerMeta.messages = workerMeta.messages ? ++workerMeta.messages : 1;
            workersMeta.set(worker, workerMeta);

            if (!message) {
                return;
            }

            if (message.cmd === 'resp' && message.mid && callQueue.has(message.mid)) {
                let { resolve, reject, timer } = callQueue.get(message.mid);
                clearTimeout(timer);
                callQueue.delete(message.mid);
                if (message.error) {
                    let err = new Error(message.error);
                    if (message.code) {
                        err.code = message.code;
                    }
                    if (message.statusCode) {
                        err.statusCode = message.statusCode;
                    }
                    if (message.info) {
                        err.info = message.info;
                    }
                    return reject(err);
                } else {
                    return resolve(message.response);
                }
            }

            if (message.cmd === 'call' && message.mid) {
                return onCommand(worker, message.message)
                    .then(response => {
                        let transferList;
                        if (response && typeof response === 'object' && response._transfer === true) {
                            if (typeof response._response === 'object' && response._response && response._response.buffer) {
                                transferList = [response._response.buffer];
                            }
                            response = response._response;
                        }

                        let callPayload = {
                            cmd: 'resp',
                            mid: message.mid,
                            response
                        };

                        try {
                            postMessage(worker, callPayload, null, transferList);
                        } catch (err) {
                            if (Buffer.isBuffer(callPayload.response)) {
                                callPayload.response = `Buffer <${callPayload.response.length}B>`;
                            }

                            logger.error({ msg: 'Failed to post state change to child', worker: worker.threadId, callPayload, err });
                        }
                    })
                    .catch(err => {
                        let callPayload = {
                            cmd: 'resp',
                            mid: message.mid,
                            error: err.message,
                            code: err.code,
                            statusCode: err.statusCode,
                            info: err.info
                        };

                        try {
                            postMessage(worker, callPayload);
                        } catch (err) {
                            logger.error({ msg: 'Failed to post state change to child', worker: worker.threadId, callPayload, err });
                        }
                    });
            }

            switch (message.cmd) {
                case 'metrics': {
                    let statUpdateKey = false;
                    let accountUpdateKey = false;

                    let { account } = message.meta || {};

                    switch (message.key) {
                        // gather for dashboard counter
                        case 'webhooks': {
                            let { status } = message.args[0] || {};
                            statUpdateKey = `${message.key}:${status}`;
                            break;
                        }

                        case 'webhookReq': {
                            break;
                        }

                        case 'events': {
                            let { event } = message.args[0] || {};
                            if (account) {
                                accountUpdateKey = `${message.key}:${event}`;
                            }

                            switch (event) {
                                case MESSAGE_NEW_NOTIFY:
                                case MESSAGE_DELETED_NOTIFY:
                                case CONNECT_ERROR_NOTIFY:
                                    statUpdateKey = `${message.key}:${event}`;
                                    break;
                            }
                            break;
                        }

                        case 'apiCall': {
                            let { statusCode } = message.args[0] || {};
                            let success = statusCode >= 200 && statusCode < 300;
                            statUpdateKey = `${message.key}:${success ? 'success' : 'fail'}`;
                            break;
                        }

                        case 'queuesProcessed': {
                            let { queue, status } = message.args[0] || {};
                            if (['submit'].includes(queue)) {
                                statUpdateKey = `${queue}:${status === 'completed' ? 'success' : 'fail'}`;
                            }
                            break;
                        }
                    }

                    if (statUpdateKey) {
                        // increment counter in redis

                        let now = new Date();

                        // we keep a separate hash value for each ISO day
                        let dateStr = `${now
                            .toISOString()
                            .substr(0, 10)
                            .replace(/[^0-9]+/g, '')}`;

                        // hash key for bucket
                        let timeStr = `${now
                            .toISOString()
                            // bucket includes 1 minute
                            .substr(0, 16)
                            .replace(/[^0-9]+/g, '')}`;

                        let hkey = `${REDIS_PREFIX}stats:${statUpdateKey}:${dateStr}`;

                        let update = redis
                            .multi()
                            .hincrby(hkey, timeStr, 1)
                            .sadd(`${REDIS_PREFIX}stats:keys`, statUpdateKey)
                            // keep alive at most 2 days
                            .expire(hkey, MAX_DAYS_STATS + 1 * 24 * 3600);

                        if (account && accountUpdateKey) {
                            // increment account specific counter
                            let accountKey = `${REDIS_PREFIX}iad:${account}`;
                            update = update.hincrby(accountKey, `stats:count:${accountUpdateKey}`, 1);
                        }

                        update.exec().catch(() => false);
                    } else if (account && accountUpdateKey) {
                        let accountKey = `${REDIS_PREFIX}iad:${account}`;
                        redis.hincrby(accountKey, `stats:count:${accountUpdateKey}`, 1).catch(() => false);
                    }

                    if (message.key && metrics[message.key] && typeof metrics[message.key][message.method] === 'function') {
                        metrics[message.key][message.method](...message.args);
                    }

                    return;
                }

                case 'settings':
                    availableIMAPWorkers.forEach(worker => {
                        try {
                            postMessage(worker, message);
                        } catch (err) {
                            logger.error({ msg: 'Failed to post command to child', worker: worker.threadId, callPayload: message, err });
                        }
                    });
                    return;

                case 'change':
                    switch (message.type) {
                        case 'smtpServerState':
                        case 'imapProxyServerState': {
                            let type = message.type.replace(/ServerState$/, '');
                            updateServerState(type, message.key, message.payload).catch(err =>
                                logger.error({ msg: `Failed to update ${type} server state`, err })
                            );
                            break;
                        }
                        default:
                            // forward all state changes to the API worker
                            for (let worker of workers.get('api') || []) {
                                try {
                                    postMessage(worker, message, true);
                                } catch (err) {
                                    logger.error({ msg: 'Failed to post state change to child', worker: worker.threadId, callPayload: message, err });
                                }
                            }
                    }
                    break;
            }

            switch (type) {
                case 'imap':
                    if (message.cmd === 'ready') {
                        availableIMAPWorkers.add(worker);
                        isOnline = true;
                        resolve(worker.threadId);

                        if (imapInitialWorkersLoaded) {
                            assignAccounts().catch(err => logger.error({ msg: 'Failed to assign accounts', n: 2, err }));
                        }
                    }
                    break;

                case 'api':
                    if (message.cmd === 'ready') {
                        isOnline = true;
                        resolve(worker.threadId);
                    }
                    break;
            }
        });
    });
};

async function call(worker, message, transferList) {
    return new Promise((resolve, reject) => {
        let mid = `${Date.now()}:${++mids}`;

        let ttl = Math.max(message.timeout || 0, EENGINE_TIMEOUT || 0);

        let timer = setTimeout(() => {
            let err = new Error('Timeout waiting for command response [T1]');
            err.statusCode = 504;
            err.code = 'Timeout';
            err.ttl = ttl;
            err.command = message;
            reject(err);
        }, ttl);

        callQueue.set(mid, { resolve, reject, timer });

        try {
            postMessage(
                worker,
                {
                    cmd: 'call',
                    mid,
                    message
                },
                false,
                transferList
            );
        } catch (err) {
            clearTimeout(timer);
            callQueue.delete(mid);
            return reject(err);
        }
    });
}

async function assignAccounts() {
    if (assigning) {
        return false;
    }
    assigning = true;
    try {
        if (!unassigned) {
            // first run
            // list all available accounts and assign to worker threads
            let accounts = await redis.smembers(`${REDIS_PREFIX}ia:accounts`);
            unassigned = new Set(accounts);
        }

        if (!availableIMAPWorkers.size || !unassigned.size) {
            // nothing to do here
            return;
        }

        logger.info({
            msg: 'Assigning connections',
            unassigned: unassigned.size,
            workersAvailable: availableIMAPWorkers.size,
            setupDelay: CONNECTION_SETUP_DELAY
        });

        for (let account of unassigned) {
            if (!availableIMAPWorkers.size) {
                // out of workers
                break;
            }

            let worker = selectRendezvousNode(account, Array.from(availableIMAPWorkers));

            if (!workerAssigned.has(worker)) {
                workerAssigned.set(worker, new Set());
            }

            workerAssigned.get(worker).add(account);
            assigned.set(account, worker);
            unassigned.delete(account);

            await call(worker, {
                cmd: 'assign',
                account,
                runIndex
            });

            if (CONNECTION_SETUP_DELAY) {
                await new Promise(r => setTimeout(r, CONNECTION_SETUP_DELAY));
            }
        }
    } finally {
        assigning = false;
    }
}

let licenseCheckTimer = false;
let checkingLicense = false;
let licenseCheckHandler = async opts => {
    if (checkingLicense) {
        return;
    }
    checkingLicense = true;
    clearTimeout(licenseCheckTimer);

    try {
        opts = opts || {};
        let { subscriptionCheckTimeout } = opts;
        let now = Date.now();
        subscriptionCheckTimeout = subscriptionCheckTimeout || SUBSCRIPTION_CHECK_TIMEOUT;

        let kv = await redis.hget(`${REDIS_PREFIX}settings`, 'kv');
        let checkKv = true;
        if (kv && typeof kv === 'string' && cv(packageData.version, Buffer.from(kv, 'hex').toString(), '<=')) {
            checkKv = false;
        }

        let ks = await redis.hget(`${REDIS_PREFIX}settings`, 'ks');
        if (ks && typeof ks === 'string') {
            let ksDate = new Date(parseInt(ks, 16));
            if (ksDate < now) {
                checkKv = true;
            }
        } else {
            checkKv = true;
        }

        if (licenseInfo.details.lt) {
            await redis.hdel(`${REDIS_PREFIX}settings`, 'subexp');
        }

        if (
            checkKv &&
            licenseInfo.active &&
            !(licenseInfo.details && licenseInfo.details.expires) &&
            !licenseInfo.details.lt &&
            (await redis.hUpdateBigger(`${REDIS_PREFIX}settings`, 'subcheck', now - subscriptionCheckTimeout, now))
        ) {
            try {
                let res = await fetchCmd(`https://postalsys.com/licenses/validate`, {
                    method: 'post',
                    headers: {
                        'User-Agent': `${packageData.name}/${packageData.version} (+${packageData.homepage})`,
                        'Content-Type': 'application/json'
                    },
                    body: JSON.stringify({
                        key: licenseInfo.details.key,
                        version: packageData.version,
                        app: '@postalsys/emailengine-app',
                        instance: (await settings.get('serviceId')) || ''
                    }),
                    dispatcher: fetchAgent
                });

                let data = await res.json();

                if (!res.ok) {
                    if (data.invalidate) {
                        let res = await redis.hUpdateBigger(`${REDIS_PREFIX}settings`, 'subexp', now, now + SUBSCRIPTION_ALLOW_DELAY);
                        if (res === 2) {
                            // grace period over
                            logger.info({ msg: 'License not valid', license: licenseInfo.details, data });
                            await redis.multi().hdel(`${REDIS_PREFIX}settings`, 'license').hdel(`${REDIS_PREFIX}settings`, 'subexp').exec();
                            licenseInfo.active = false;
                            licenseInfo.details = false;
                            licenseInfo.type = packageData.license;
                        }
                    }
                } else {
                    await redis.hdel(`${REDIS_PREFIX}settings`, 'subexp');
                    await redis.hset(`${REDIS_PREFIX}settings`, 'kv', Buffer.from(packageData.version).toString('hex'));
                    if (data.validatedUntil) {
                        let validatedUntil = new Date(data.validatedUntil);
                        let nextCheck = Math.min(now + MAX_LICENSE_CHECK_DELAY, validatedUntil.getTime());
                        await redis.hset(`${REDIS_PREFIX}settings`, 'ks', new Date(nextCheck).getTime().toString(16));
                    }
                }
            } catch (err) {
                logger.error({ msg: 'Failed to validate license', err });
            }
        }

        if (licenseInfo.active && licenseInfo.details && licenseInfo.details.expires && new Date(licenseInfo.details.expires).getTime() < Date.now()) {
            // clear expired license

            logger.info({ msg: 'License expired', license: licenseInfo.details });

            licenseInfo.active = false;
            licenseInfo.details = false;
        }

        if (!licenseInfo.active && !suspendedWorkerTypes.size) {
            logger.info({ msg: 'No active license, shutting down workers after 15 minutes of activity' });

            for (let type of ['imap', 'submit', 'smtp', 'webhooks', 'imapProxy']) {
                suspendedWorkerTypes.add(type);
                if (workers.has(type)) {
                    for (let worker of workers.get(type).values()) {
                        worker.terminate();
                    }
                }
            }
        } else if (licenseInfo.active && suspendedWorkerTypes.size) {
            // re-enable missing workers
            for (let type of suspendedWorkerTypes) {
                suspendedWorkerTypes.delete(type);
                switch (type) {
                    case 'smtp':
                    case 'imapProxy':
                        {
                            let serverEnabled = await settings.get(`${type}ServerEnabled`);
                            if (serverEnabled) {
                                // single SMTP interface worker
                                await spawnWorker(type);
                            }
                        }
                        break;
                    default:
                        if (config.workers && config.workers[type]) {
                            for (let i = 0; i < config.workers[type]; i++) {
                                await spawnWorker(type);
                            }
                        }
                }
            }
        }
    } finally {
        checkingLicense = false;
        licenseCheckTimer = setTimeout(checkActiveLicense, LICENSE_CHECK_TIMEOUT);
        licenseCheckTimer.unref();
    }
};

function checkActiveLicense() {
    clearTimeout(licenseCheckTimer);
    licenseCheckHandler().catch(err => {
        logger.error('Failed to process license checker', err);
    });
}

let processCheckUpgrade = async () => {
    try {
        let updateInfo = await checkForUpgrade();
        if (updateInfo.canUpgrade) {
            logger.info({ msg: 'Found an upgrade for EmailEngine', updateInfo });

            updateInfo.checked = Date.now();
            await redis.hset(`${REDIS_PREFIX}settings`, 'upgrade', JSON.stringify(updateInfo));
        } else {
            await redis.hdel(`${REDIS_PREFIX}settings`, 'upgrade');
        }
    } catch (err) {
        logger.error({ msg: 'Failed to check updates', err });
    }
};

let upgradeCheckTimer = false;
let upgradeCheckHandler = async () => {
    let upgradeInfoExists = await redis.hexists(`${REDIS_PREFIX}settings`, 'upgrade');
    if (!upgradeInfoExists) {
        // nothing to do here
        return;
    }
    await processCheckUpgrade();
    upgradeCheckTimer = setTimeout(checkUpgrade, UPGRADE_CHECK_TIMEOUT);
    upgradeCheckTimer.unref();
};

function checkUpgrade() {
    clearTimeout(upgradeCheckTimer);
    upgradeCheckHandler().catch(err => {
        logger.error('Failed to process upgrade check', err);
    });
}

// measure Redis ping once in every 10 seconds

let redisPingCounter = [];

function getRedisPing() {
    if (!redisPingCounter.length) {
        return null;
    }

    let entries = []
        .concat(redisPingCounter)
        .slice(-34)
        .sort((a, b) => a - b);

    // remove 2 highest and lowest if possible
    for (let i = 0; i < 2; i++) {
        if (entries.length > 4) {
            entries.shift();
            entries.pop();
        }
    }

    let sum = 0;
    for (let entry of entries) {
        sum += entry;
    }

    return Math.round(sum / entries.length);
}

const REDIS_PING_TIMEOUT = 10 * 1000;
let redisPingTimer = false;

const getCurrentRedisPing = async () => {
    try {
        // this request is not timed, it is to ensure that there is an open connection
        await redis.ping();

        let startTime = process.hrtime.bigint();
        await redis.ping();
        let endTime = process.hrtime.bigint();

        let duration = Number(endTime - startTime);

        return duration;
    } catch (err) {
        logger.error({ msg: 'Failed to run Redis ping', err });
    }
    return 0;
};

const processRedisPing = async () => {
    try {
        let duration = await getCurrentRedisPing();
        redisPingCounter.push(duration);
        if (redisPingCounter.length > 300) {
            redisPingCounter = redisPingCounter.slice(0, 150);
        }
        return duration;
    } catch (err) {
        logger.error({ msg: 'Failed to run Redis ping', err });
    }
};

const redisPingHandler = async () => {
    await processRedisPing();
    redisPingTimer = setTimeout(checkRedisPing, REDIS_PING_TIMEOUT);
    redisPingTimer.unref();
};

function checkRedisPing() {
    clearTimeout(redisPingTimer);
    redisPingHandler().catch(err => {
        logger.error('Failed to process Redis Ping', err);
    });
}

async function updateQueueCounters() {
    metrics.emailengineConfig.set({ version: 'v' + packageData.version }, 1);
    metrics.emailengineConfig.set({ config: 'uvThreadpoolSize' }, Number(process.env.UV_THREADPOOL_SIZE));
    metrics.emailengineConfig.set({ config: 'workersImap' }, config.workers.imap);
    metrics.emailengineConfig.set({ config: 'workersWebhooks' }, config.workers.webhooks);
    metrics.emailengineConfig.set({ config: 'workersSubmission' }, config.workers.submit);

    for (let queue of ['notify', 'submit', 'documents']) {
        const [resActive, resDelayed, resPaused, resWaiting] = await redis
            .multi()
            .llen(`${REDIS_PREFIX}bull:${queue}:active`)
            .zcard(`${REDIS_PREFIX}bull:${queue}:delayed`)
            .llen(`${REDIS_PREFIX}bull:${queue}:paused`)
            .llen(`${REDIS_PREFIX}bull:${queue}:wait`)
            .exec();
        if (resActive[0] || resDelayed[0] || resPaused[0] || resWaiting[0]) {
            // counting failed
            logger.error({ msg: 'Failed to count queue length', queue, active: resActive, delayed: resDelayed, paused: resPaused, waiting: resWaiting });
            return false;
        }

        metrics.queues.set({ queue: `${queue}`, state: `active` }, Number(resActive[1]) || 0);
        metrics.queues.set({ queue: `${queue}`, state: `delayed` }, Number(resDelayed[1]) || 0);
        metrics.queues.set({ queue: `${queue}`, state: `paused` }, Number(resPaused[1]) || 0);
        metrics.queues.set({ queue: `${queue}`, state: `waiting` }, Number(resWaiting[1]) || 0);
    }

    try {
        let redisInfo = await getRedisStats(redis);

        if (redisInfo.redis_version) {
            metrics.redisVersion.set({ version: 'v' + redisInfo.redis_version }, 1);
        }

        metrics.redisUptimeInSeconds.set(Number(redisInfo.uptime_in_seconds) || 0);

        metrics.redisPing.set((await getCurrentRedisPing()) || 0);

        metrics.redisRejectedConnectionsTotal.set(Number(redisInfo.rejected_connections) || 0);
        metrics.redisConfigMaxclients.set(Number(redisInfo.maxclients) || 0);
        metrics.redisConnectedClients.set(Number(redisInfo.connected_clients) || 0);
        metrics.redisSlowlogLength.set(Number(redisInfo.slowlog_length) || 0);

        metrics.redisCommandsDurationSecondsTotal.set(Math.ceil((Number(redisInfo.cmdstat_total && redisInfo.cmdstat_total.usec) || 0) / 1000000));
        metrics.redisCommandsProcessedTotal.set(Number(redisInfo.cmdstat_total && redisInfo.cmdstat_total.calls) || 0);

        metrics.redisKeyspaceHitsTotal.set(Number(redisInfo.keyspace_hits) || 0);
        metrics.redisKeyspaceMissesTotal.set(Number(redisInfo.keyspace_misses) || 0);

        metrics.redisEvictedKeysTotal.set(Number(redisInfo.evicted_keys) || 0);

        metrics.redisMemoryUsedBytes.set(Number(redisInfo.used_memory) || 0);
        metrics.redisMemoryMaxBytes.set(Number(redisInfo.maxmemory) || Number(redisInfo.total_system_memory) || 0);

        metrics.redisMemFragmentationRatio.set(Number(redisInfo.mem_fragmentation_ratio) || 0);

        Object.keys(redisInfo).forEach(key => {
            if (/^db\d+$/.test(key)) {
                //redisKeyCount
                metrics.redisKeyCount.set({ db: key }, Number(redisInfo[key].keys) || 0);
            }

            if (key.indexOf('cmdstat_') === 0) {
                let cmd = key.substr('cmdstat_'.length);
                metrics.redisCommandRuns.set({ command: cmd }, Number(redisInfo[key].calls) || 0);

                if (redisInfo[key].failed_calls) {
                    metrics.redisCommandRunsFailed.set({ command: cmd, status: 'failed' }, Number(redisInfo[key].failed_calls) || 0);
                }

                if (redisInfo[key].rejected_calls) {
                    metrics.redisCommandRunsFailed.set({ command: cmd, status: 'rejected' }, Number(redisInfo[key].rejected_calls) || 0);
                }
            }
        });

        metrics.redisLastSaveTime.set(Number(redisInfo.rdb_last_save_time) || 0);
        metrics.redisOpsPerSec.set(Number(redisInfo.instantaneous_ops_per_sec) || 0);
    } catch (err) {
        logger.error({ msg: 'Failed to update query counters', err });
    }
}

async function onCommand(worker, message) {
    switch (message.cmd) {
        case 'metrics':
            await updateQueueCounters();
            return promClient.register.metrics();

        case 'structuredMetrics': {
            let connections = {};

            for (let key of Object.keys(metrics.imapConnections.hashMap)) {
                if (key.indexOf('status:') === 0) {
                    let metric = metrics.imapConnections.hashMap[key];
                    connections[metric.labels.status] = metric.value;
                }
            }

            return { connections, redisPing: await getRedisPing() };
        }

        case 'imapWorkerCount': {
            return { workers: availableIMAPWorkers.size };
        }

        case 'checkLicense':
            try {
                await licenseCheckHandler({
                    subscriptionCheckTimeout: 60 * 1000
                });
            } catch (err) {
                // ignore
            }
            return licenseInfo;

        case 'license':
            if (!licenseInfo.active && suspendedWorkerTypes.size) {
                return Object.assign({}, licenseInfo, { suspended: true });
            }
            return licenseInfo;

        case 'updateLicense': {
            try {
                const licenseFile = message.license;

                let licenseData = await checkLicense(licenseFile);
                if (!licenseData) {
                    throw new Error('Failed to verify provided license');
                }

                logger.info({ msg: 'Loaded license', license: licenseData, source: 'API' });

                await setLicense(licenseData, licenseFile);

                licenseInfo.active = true;
                licenseInfo.details = licenseData;
                licenseInfo.type = 'EmailEngine License';

                // re-enable workers
                checkActiveLicense();

                return licenseInfo;
            } catch (err) {
                logger.fatal({ msg: 'Failed to verify provided license', source: 'API', err });
                return false;
            }
        }

        case 'removeLicense': {
            try {
                await redis.multi().hdel(`${REDIS_PREFIX}settings`, 'license').hdel(`${REDIS_PREFIX}settings`, 'subexp').exec();

                licenseInfo.active = false;
                licenseInfo.details = false;
                licenseInfo.type = packageData.license;

                return licenseInfo;
            } catch (err) {
                logger.fatal({ msg: 'Failed to remove existing license', err });
                return false;
            }
        }

        case 'kill-thread': {
            for (let [, workerSet] of workers) {
                if (workerSet && workerSet.size) {
                    for (let worker of workerSet) {
                        if (worker.threadId === message.thread) {
                            logger.info({ msg: 'Requested thread kill', thread: message.thread });
                            return await worker.terminate();
                        }
                    }
                }
            }

            return false;
        }

        case 'snapshot-thread': {
            if (message.thread === 0) {
                logger.info({ msg: 'Requested snapshot for a thread', thread: message.thread });
                const stream = v8.getHeapSnapshot();
                if (stream) {
                    return { _transfer: true, _response: await download(stream) };
                }
                return false;
            }

            for (let [, workerSet] of workers) {
                if (workerSet && workerSet.size) {
                    for (let worker of workerSet) {
                        if (worker.threadId === message.thread) {
                            logger.info({ msg: 'Requested snapshot for a thread', thread: message.thread });

                            const stream = await worker.getHeapSnapshot({ exposeInternals: true, exposeNumericValues: true });
                            if (stream) {
                                return { _transfer: true, _response: await download(stream) };
                            }
                            return false;
                        }
                    }
                }
            }

            return false;
        }

        // run these in main process to avoid polluting RAM with the memory hungry tokenization library
        case 'generateSummary': {
            let requestOpts = {
                verbose: getBoolean(process.env.EE_OPENAPI_VERBOSE)
            };

            let openAiAPIKey = message.data.openAiAPIKey || (await settings.get('openAiAPIKey'));

            if (!openAiAPIKey) {
                throw new Error(`OpenAI API key is not set`);
            }

            let openAiModel = message.data.openAiModel || (await settings.get('openAiModel'));
            if (openAiModel) {
                requestOpts.gptModel = openAiModel;
            }

            let openAiAPIUrl = message.data.openAiAPIUrl || (await settings.get('openAiAPIUrl'));
            if (openAiAPIUrl) {
                requestOpts.baseApiUrl = openAiAPIUrl;
            }

            let openAiTemperature = message.data.openAiTemperature || (await settings.get('openAiTemperature'));
            if (openAiTemperature) {
                requestOpts.temperature = openAiTemperature;
            }

            let openAiTopP = message.data.openAiTopP || (await settings.get('openAiTopP'));
            if (openAiTopP) {
                requestOpts.topP = openAiTopP;
            }

            switch (openAiModel) {
                case 'gpt-4':
                    requestOpts.maxTokens = 6500;
                    break;
                case 'gpt-3.5-turbo':
                case 'gpt-3.5-turbo-instruct':
                default:
                    requestOpts.maxTokens = 3000;
                    break;
            }

            requestOpts.user = message.data.account;

            let userPrompt = message.data.openAiPrompt || ((await settings.get('openAiPrompt')) || '').toString();
            if (userPrompt.trim()) {
                requestOpts.userPrompt = userPrompt;
            }

            return await generateSummary(message.data.message, openAiAPIKey, requestOpts);
        }

        // run these in main process to avoid polluting RAM with the memory hungry tokenization library
        case 'generateEmbeddings': {
            let requestOpts = {
                verbose: getBoolean(process.env.EE_OPENAPI_VERBOSE)
            };

            let openAiAPIKey = message.data.openAiAPIKey || (await settings.get('openAiAPIKey'));

            if (!openAiAPIKey) {
                throw new Error(`OpenAI API key is not set`);
            }

            let openAiAPIUrl = message.data.openAiAPIUrl || (await settings.get('openAiAPIUrl'));
            if (openAiAPIUrl) {
                requestOpts.baseApiUrl = openAiAPIUrl;
            }

            requestOpts.user = message.data.account;

            const embeddings = await generateEmbeddings(message.data.message, openAiAPIKey, requestOpts);
            if (!Array.isArray(embeddings?.embeddings)) {
                return false;
            }

            for (let value of embeddings.embeddings) {
                for (const key of Object.keys(value)) {
                    if (/^_/.test(key)) {
                        delete value[key];
                    }
                }
            }

            return embeddings;
        }

        case 'embeddingsQuery': {
            let requestOpts = {
                verbose: getBoolean(process.env.EE_OPENAPI_VERBOSE)
            };

            let openAiAPIKey = message.data.openAiAPIKey || (await settings.get('openAiAPIKey'));

            if (!openAiAPIKey) {
                throw new Error(`OpenAI API key is not set`);
            }

            let openAiAPIUrl = message.data.openAiAPIUrl || (await settings.get('openAiAPIUrl'));
            if (openAiAPIUrl) {
                requestOpts.baseApiUrl = openAiAPIUrl;
            }

            let openAiModel = message.data.openAiModel || (await settings.get('documentStoreChatModel')) || (await settings.get('openAiModel'));
            if (openAiModel) {
                requestOpts.gptModel = openAiModel;
            }

            switch (openAiModel) {
                case 'gpt-4':
                    requestOpts.maxTokens = 6500;
                    break;
                case 'gpt-3.5-turbo':
                case 'gpt-3.5-turbo-instruct':
                default:
                    requestOpts.maxTokens = 3000;
                    break;
            }

            requestOpts.user = message.data.account;
            requestOpts.temperature = 0.4;

            requestOpts.question = message.data.question;
            requestOpts.contextChunks = message.data.contextChunks;
            requestOpts.userData = message.data.userData;

            let response = await embeddingsQuery(openAiAPIKey, requestOpts);

            if (response?.['Message-ID']) {
                response.messageId = response?.['Message-ID'];
                delete response?.['Message-ID'];
            }
            if (response?.messageId) {
                response.messageId = [].concat(response?.messageId || []).map(value => (value || '').toString().trim().replace(/^<?/, '<').replace(/>?$/, '>'));
            }

            if (response?.answer) {
                if (typeof response.answer === 'object') {
                    response.answer = JSON.stringify(response.answer);
                } else {
                    response.answer = response.answer.toString();
                }
            }

            for (const key of Object.keys(response)) {
                if (/^_/.test(key)) {
                    delete response[key];
                }
            }

            return response;
        }

        case 'questionQuery': {
            let requestOpts = {
                verbose: getBoolean(process.env.EE_OPENAPI_VERBOSE)
            };

            let openAiAPIKey = message.data.openAiAPIKey || (await settings.get('openAiAPIKey'));

            if (!openAiAPIKey) {
                throw new Error(`OpenAI API key is not set`);
            }

            let openAiAPIUrl = message.data.openAiAPIUrl || (await settings.get('openAiAPIUrl'));
            if (openAiAPIUrl) {
                requestOpts.baseApiUrl = openAiAPIUrl;
            }

            let openAiModel = message.data.openAiModel || 'gpt-3.5-turbo-instruct';
            if (openAiModel) {
                requestOpts.gptModel = openAiModel;
            }

            requestOpts.user = message.data.account;

            let response = await questionQuery(message.data.question, openAiAPIKey, requestOpts);

            for (const key of Object.keys(response)) {
                if (/^_/.test(key)) {
                    delete response[key];
                }
            }

            return response;
        }

        // run these in main process to avoid polluting RAM with the memory hungry tokenization library
        case 'generateChunkEmbeddings': {
            let requestOpts = {
                verbose: getBoolean(process.env.EE_OPENAPI_VERBOSE)
            };

            let openAiAPIKey = message.data.openAiAPIKey || (await settings.get('openAiAPIKey'));

            if (!openAiAPIKey) {
                throw new Error(`OpenAI API key is not set`);
            }

            let openAiAPIUrl = message.data.openAiAPIUrl || (await settings.get('openAiAPIUrl'));
            if (openAiAPIUrl) {
                requestOpts.baseApiUrl = openAiAPIUrl;
            }

            requestOpts.user = message.data.account;

            const data = await getChunkEmbeddings(message.data.message, openAiAPIKey, requestOpts);

            return data;
        }

        case 'openAiListModels': {
            let requestOpts = {
                verbose: getBoolean(process.env.EE_OPENAPI_VERBOSE)
            };

            let openAiAPIKey = message.data.openAiAPIKey || (await settings.get('openAiAPIKey'));

            if (!openAiAPIKey) {
                throw new Error(`OpenAI API key is not set`);
            }

            let openAiAPIUrl = message.data.openAiAPIUrl || (await settings.get('openAiAPIUrl'));
            if (openAiAPIUrl) {
                requestOpts.baseApiUrl = openAiAPIUrl;
            }

            requestOpts.user = message.data.account;

            const data = await openAiListModels(openAiAPIKey, requestOpts);

            return data;
        }

        case 'openAiDefaultPrompt': {
            return openAiDefaultPrompt;
        }

        case 'threads': {
            let threadsInfo = [Object.assign({ type: 'main', isMain: true, threadId: 0, online: NOW }, threadStats.usage())];

            for (let [type, workerSet] of workers) {
                if (workerSet && workerSet.size) {
                    for (let worker of workerSet) {
                        let resourceUsage;
                        try {
                            resourceUsage = await call(worker, { cmd: 'resource-usage' });
                        } catch (err) {
                            resourceUsage = {
                                resourceUsageError: {
                                    error: err.message,
                                    code: err.code
                                }
                            };
                        }

                        let threadData = Object.assign({ type, threadId: worker.threadId, resourceLimits: worker.resourceLimits }, resourceUsage);

                        if (workerAssigned.has(worker)) {
                            threadData.accounts = workerAssigned.get(worker).size;
                        }

                        let workerMeta = workersMeta.has(worker) ? workersMeta.get(worker) : {};
                        for (let key of Object.keys(workerMeta)) {
                            threadData[key] = workerMeta[key];
                        }

                        threadsInfo.push(threadData);
                    }
                }
            }

            threadsInfo.forEach(threadInfo => {
                threadInfo.description = THREAD_NAMES[threadInfo.type];
                if (THREAD_CONFIG_VALUES[threadInfo.type]) {
                    threadInfo.config = THREAD_CONFIG_VALUES[threadInfo.type];
                }
            });

            return threadsInfo;
        }

        case 'rate-limit': {
            return await checkRateLimit(message.key, message.count, message.allowed, message.windowSize);
        }

        case 'unsubscribe':
            sendWebhook(message.account, LIST_UNSUBSCRIBE_NOTIFY, message.payload).catch(err =>
                logger.error({ msg: 'Failed to send an unsubscribe webhook', err })
            );
            return;

        case 'subscribe':
            sendWebhook(message.account, LIST_SUBSCRIBE_NOTIFY, message.payload).catch(err =>
                logger.error({ msg: 'Failed to send an subscribe webhook', err })
            );
            return;

        case 'new':
            unassigned.add(message.account);
            assignAccounts()
                .then(() => sendWebhook(message.account, ACCOUNT_ADDED_NOTIFY, { account: message.account }))
                .catch(err => logger.error({ msg: 'Failed to assign accounts', n: 3, err }));
            return;

        case 'delete':
            unassigned.delete(message.account); // if set
            clearUnassignmentCounter(message.account);
            if (assigned.has(message.account)) {
                let assignedWorker = assigned.get(message.account);
                if (workerAssigned.has(assignedWorker)) {
                    workerAssigned.get(assignedWorker).delete(message.account);
                    if (!workerAssigned.get(assignedWorker).size) {
                        // last item in the worker accounts
                        workerAssigned.delete(assignedWorker);
                    }
                }

                call(assignedWorker, message)
                    .then(() => logger.debug('worker processed'))
                    .catch(err => logger.error({ msg: 'Failed to clean an assigned worker', err }));
            }
            sendWebhook(message.account, ACCOUNT_DELETED_NOTIFY, { account: message.account }).catch(err =>
                logger.error({ msg: 'Failed to send a deletion webhook', err })
            );
            return;

        case 'runIndex': {
            return runIndex;
        }

        case 'update':
        case 'sync':
        case 'pause':
        case 'resume':
        case 'reconnect':
            if (assigned.has(message.account)) {
                let assignedWorker = assigned.get(message.account);
                call(assignedWorker, message)
                    .then(() => logger.debug('worker processed'))
                    .catch(err => logger.error({ msg: 'Failed to call sync from a worker', err }));
            }
            return;

        case 'smtpReload':
        case 'imapProxyReload':
            {
                let type = message.cmd.replace(/Reload$/, '');
                let hasWorkers = workers.has(type) && workers.get(type).size;
                // reload (or kill) SMTP submission worker
                if (hasWorkers) {
                    for (let worker of workers.get(type).values()) {
                        worker.terminate();
                    }
                } else {
                    let serverEnabled = await settings.get(`${type}ServerEnabled`);
                    if (serverEnabled) {
                        // spawn a new worker
                        await spawnWorker(type);
                    }
                }
            }
            break;

        case 'listMessages':
        case 'getRawMessage':
        case 'getText':
        case 'getMessage':
        case 'updateMessage':
        case 'updateMessages':
        case 'listMailboxes':
        case 'moveMessage':
        case 'moveMessages':
        case 'deleteMessage':
        case 'deleteMessages':
        case 'getQuota':
        case 'createMailbox':
        case 'renameMailbox':
        case 'deleteMailbox':
        case 'submitMessage':
        case 'queueMessage':
        case 'uploadMessage':
        case 'getAttachment': {
            if (!assigned.has(message.account)) {
                return NO_ACTIVE_HANDLER_RESP;
            }

            let assignedWorker = assigned.get(message.account);

            let transferList = [];
            if (['getRawMessage', 'getAttachment'].includes(message.cmd) && message.port) {
                transferList.push(message.port);
            }

            if (['submitMessage', 'queueMessage'].includes(message.cmd) && typeof message.raw === 'object') {
                transferList.push(message.raw);
            }

            return await call(assignedWorker, message, transferList);
        }

        case 'subconnections': {
            if (!assigned.has(message.account)) {
                return [];
            }

            let assignedWorker = assigned.get(message.account);
            return await call(assignedWorker, message, []);
        }

        case 'googlePubSub': {
            // notify all webhook workers about a new pubsub app
            for (let worker of workers.get('webhooks')) {
                await call(worker, message);
            }
            return true;
        }

        case 'externalNotify': {
            for (let account of message.accounts) {
                if (!assigned.has(account)) {
                    continue;
                }

                let assignedWorker = assigned.get(account);
                try {
                    await call(assignedWorker, { cmd: 'externalNotify', account, historyId: message.historyId });
                } catch (err) {
                    logger.error({ msg: 'Failed to notify worker about account changes', cmd: 'externalNotify', account, historyId: message.historyId, err });
                }
            }
            return true;
        }
    }

    return 999;
}

let metricsResult = {};
async function collectMetrics() {
    // reset all counters
    Object.keys(metricsResult || {}).forEach(key => {
        metricsResult[key] = 0;
    });

    if (workers.has('imap')) {
        let imapWorkers = workers.get('imap');
        for (let imapWorker of imapWorkers) {
            if (!availableIMAPWorkers.has(imapWorker)) {
                // worker not available yet
                continue;
            }

            try {
                let workerStats = await call(imapWorker, { cmd: 'countConnections' });
                Object.keys(workerStats || {}).forEach(status => {
                    if (!metricsResult[status]) {
                        metricsResult[status] = 0;
                    }
                    metricsResult[status] += Number(workerStats[status]) || 0;
                });
            } catch (err) {
                logger.error({ msg: 'Failed to count connections', err });
            }
        }
    }

    Object.keys(metricsResult).forEach(status => {
        metrics.imapConnections.set({ status }, metricsResult[status]);
    });
}

const closeQueues = cb => {
    let proms = [];
    if (queueEvents.notify) {
        proms.push(queueEvents.notify.close());
    }

    if (queueEvents.submit) {
        proms.push(queueEvents.submit.close());
    }

    if (queueEvents.documents) {
        proms.push(queueEvents.documents.close());
    }

    if (!proms.length) {
        return setImmediate(() => cb());
    }

    let returned;

    let closeTimeout = setTimeout(() => {
        clearTimeout(closeTimeout);
        if (returned) {
            return;
        }
        returned = true;
        cb();
    }, 2500);

    Promise.allSettled(proms).then(() => {
        clearTimeout(closeTimeout);
        if (returned) {
            return;
        }
        returned = true;
        cb();
    });
};

process.on('SIGTERM', () => {
    logger.info({ msg: 'Close signal received', signal: 'SIGTERM', isClosing });
    if (isClosing) {
        return;
    }
    isClosing = true;
    closeQueues(() => {
        logger.flush(() => process.exit());
    });
});

process.on('SIGINT', () => {
    logger.info({ msg: 'Close signal received', signal: 'SIGINT', isClosing });
    if (isClosing) {
        return;
    }
    isClosing = true;
    closeQueues(() => {
        logger.flush(() => process.exit());
    });
});

// START APPLICATION

const startApplication = async () => {
    runIndex = await redis.hincrby(`${REDIS_PREFIX}settings`, 'run', 1);

    // process license
    if (config.licensePath) {
        try {
            let stat = await fs.stat(config.licensePath);
            if (!stat.isFile()) {
                throw new Error(`Provided license key is not a regular file`);
            }
            const licenseFile = await fs.readFile(config.licensePath, 'utf-8');
            let licenseData = await checkLicense(licenseFile);
            if (!licenseData) {
                throw new Error('Failed to verify provided license key');
            }
            logger.info({ msg: 'Loaded license key', license: licenseData, source: config.licensePath });

            await setLicense(licenseData, licenseFile);
        } catch (err) {
            logger.fatal({ msg: 'Failed to verify provided license key file', source: config.licensePath, err });
            return logger.flush(() => process.exit(13));
        }
    }

    const preparedLicenseString = readEnvValue('EENGINE_PREPARED_LICENSE') || config.preparedLicense;
    if (preparedLicenseString) {
        try {
            let imported = await settings.importLicense(preparedLicenseString, checkLicense);
            if (imported) {
                logger.info({ msg: 'Imported license key', source: 'import' });
            }
        } catch (err) {
            logger.fatal({ msg: 'Failed to verify provided license key data', source: 'import', err });
            return logger.flush(() => process.exit(13));
        }
    }

    let licenseFile = await redis.hget(`${REDIS_PREFIX}settings`, 'license');
    if (licenseFile) {
        try {
            let licenseData = await checkLicense(licenseFile);
            if (!licenseData) {
                throw new Error('Failed to verify provided license key');
            }
            licenseInfo.active = true;
            licenseInfo.details = licenseData;
            licenseInfo.type = 'EmailEngine License';
            if (!config.licensePath) {
                logger.info({ msg: 'Loaded license', license: licenseData, source: 'db' });
            }
        } catch (err) {
            logger.fatal({ msg: 'Failed to verify stored license key', content: licenseFile, err });
        }
    }

    if (!licenseInfo.active) {
        logger.fatal({ msg: 'No active license key provided. Running in limited mode.' });
    }

    // check for updates, run as a promise to not block other activities
    processCheckUpgrade().catch(err => {
        logger.error({ msg: 'Failed to process upgrade check', err });
    });

    if (preparedSettings) {
        // set up configuration
        logger.debug({ msg: 'Updating application settings', settings: preparedSettings });

        for (let key of Object.keys(preparedSettings)) {
            await settings.set(key, preparedSettings[key]);
        }
    }

    // prepare some required configuration values
    let existingServiceId = await settings.get('serviceId');
    if (existingServiceId === null) {
        await settings.set('serviceId', crypto.randomBytes(16).toString('hex'));
    }

    let existingSmtpEnabled = await settings.get('smtpServerEnabled');
    if (existingSmtpEnabled === null) {
        await settings.set('smtpServerEnabled', !!SMTP_ENABLED);
    }

    let existingSmtpSecret = await settings.get('smtpServerPassword');
    if (existingSmtpSecret === null) {
        await settings.set('smtpServerPassword', SMTP_SECRET || null);
    }

    let existingSmtpAuthEnabled = await settings.get('smtpServerAuthEnabled');
    if (existingSmtpAuthEnabled === null && (existingSmtpSecret || existingSmtpSecret === null)) {
        await settings.set('smtpServerAuthEnabled', true);
    }

    let existingSmtpPort = await settings.get('smtpServerPort');
    if (existingSmtpPort === null) {
        await settings.set('smtpServerPort', SMTP_PORT);
    }

    let existingSmtpHost = await settings.get('smtpServerHost');
    if (existingSmtpHost === null) {
        await settings.set('smtpServerHost', SMTP_HOST);
    }

    let existingSmtpProxy = await settings.get('smtpServerProxy');
    if (existingSmtpProxy === null) {
        await settings.set('smtpServerProxy', SMTP_PROXY);
    }

    let existingImapProxyEnabled = await settings.get('imapProxyServerEnabled');
    if (existingImapProxyEnabled === null) {
        await settings.set('imapProxyServerEnabled', !!IMAP_PROXY_ENABLED);
    }

    let existingImapProxySecret = await settings.get('imapProxyServerPassword');
    if (existingImapProxySecret === null) {
        await settings.set('imapProxyServerPassword', IMAP_PROXY_SECRET || null);
    }

    let existingImapProxyPort = await settings.get('imapProxyServerPort');
    if (existingImapProxyPort === null) {
        await settings.set('imapProxyServerPort', IMAP_PROXY_PORT);
    }

    let existingImapProxyHost = await settings.get('imapProxyServerHost');
    if (existingImapProxyHost === null) {
        await settings.set('imapProxyServerHost', IMAP_PROXY_HOST);
    }

    let existingImapProxyProxy = await settings.get('imapProxyServerProxy');
    if (existingImapProxyProxy === null) {
        await settings.set('imapProxyServerProxy', IMAP_PROXY_PROXY);
    }

    let existingEnableApiProxy = await settings.get('enableApiProxy');
    if (existingEnableApiProxy === null) {
        await settings.set('enableApiProxy', HAS_API_PROXY_SET ? API_PROXY : true);
    }

    let existingServiceSecret = await settings.get('serviceSecret');
    if (existingServiceSecret === null) {
        await settings.set('serviceSecret', crypto.randomBytes(16).toString('hex'));
    }

    let existingQueueKeep = await settings.get('queueKeep');
    if (existingQueueKeep === null) {
        let QUEUE_KEEP = Math.max((readEnvValue('EENGINE_QUEUE_REMOVE_AFTER') && Number(readEnvValue('EENGINE_QUEUE_REMOVE_AFTER'))) || 0, 0);
        await settings.set('queueKeep', QUEUE_KEEP);
    }

    let existingNotifyText = await settings.get('notifyText');
    if (existingNotifyText === null) {
        await settings.set('notifyText', true);
    }

    let existingNotifyTextSize = await settings.get('notifyTextSize');
    if (existingNotifyTextSize === null) {
        await settings.set('notifyTextSize', 2 * 1024 * 1024); // set default max text size in webhooks to 2MB
    }

    let existingScriptEnv = await settings.get('scriptEnv');
    if (existingScriptEnv === null) {
        await settings.set('scriptEnv', {}); // empty object
    }

    if (preparedToken) {
        try {
            let imported = await tokens.setRawData(preparedToken);
            if (imported) {
                logger.debug({ msg: 'Imported prepared token', token: preparedToken.id });
            } else {
                logger.debug({ msg: 'Skipped prepared token', token: preparedToken.id });
            }
        } catch (err) {
            logger.error({ msg: 'Failed to import token', token: preparedToken.id });
        }
    }

    if (preparedPassword) {
        try {
            let authData = await settings.get('authData');

            authData = authData || {};
            authData.user = authData.user || 'admin';
            authData.password = preparedPassword;
            authData.passwordVersion = Date.now();

            await settings.set('authData', authData);
            logger.debug({ msg: 'Imported hashed password', hash: preparedPassword });
        } catch (err) {
            logger.error({ msg: 'Failed to import password', hash: preparedPassword });
        }
    }

    // renew encryiption secret, if needed
    await getSecret();

    // ensure password for cookie based auth
    let cookiePassword = await settings.get('cookiePassword');
    if (!cookiePassword) {
        cookiePassword = crypto.randomBytes(32).toString('base64');
        await settings.set('cookiePassword', cookiePassword);
    }

    // -- START WORKER THREADS

    // single worker for HTTP, start first for health checks
    await spawnWorker('api');

    // multiple IMAP connection handlers
    let workerPromises = [];
    for (let i = 0; i < config.workers.imap; i++) {
        workerPromises.push(spawnWorker('imap'));
    }
    let threadIds = await Promise.all(workerPromises);
    logger.info({ msg: 'IMAP workers started', workers: config.workers.imap, threadIds });

    try {
        await assignAccounts();
    } catch (err) {
        logger.error({ msg: 'Failed to assign accounts', n: 2, err });
    }
    imapInitialWorkersLoaded = true;

    for (let i = 0; i < config.workers.webhooks; i++) {
        await spawnWorker('webhooks');
    }

    for (let i = 0; i < config.workers.submit; i++) {
        await spawnWorker('submit');
    }

    // single worker to process events in order
    await spawnWorker('documents');

    if (await settings.get('smtpServerEnabled')) {
        // single SMTP interface worker
        await spawnWorker('smtp');
    }

    if (await settings.get('imapProxyServerEnabled')) {
        // single IMAP proxy interface worker
        await spawnWorker('imapProxy');
    }
};

startApplication()
    .then(() => {
        // start collecting metrics
        setInterval(() => {
            collectMetrics().catch(err => logger.error({ msg: 'Failed to collect metrics', err }));
        }, 1000).unref();

        licenseCheckTimer = setTimeout(checkActiveLicense, LICENSE_CHECK_TIMEOUT);
        licenseCheckTimer.unref();

        upgradeCheckTimer = setTimeout(checkUpgrade, UPGRADE_CHECK_TIMEOUT);
        upgradeCheckTimer.unref();

        redisPingTimer = setTimeout(checkRedisPing, REDIS_PING_TIMEOUT);
        redisPingTimer.unref();

        queueEvents.notify = new QueueEvents('notify', Object.assign({}, queueConf));
        queueEvents.submit = new QueueEvents('submit', Object.assign({}, queueConf));
        queueEvents.documents = new QueueEvents('documents', Object.assign({}, queueConf));
    })
    .catch(err => {
        logger.fatal({ msg: 'Failed to start application', err });
        logger.flush(() => process.exit(1));
    });