Skip to content

Latest commit

 

History

History
58 lines (51 loc) · 2.74 KB

Design.md

File metadata and controls

58 lines (51 loc) · 2.74 KB
Raw

Design

Overview of the ddprof architecture

Architecture

ddprof is a sample based profiler. It uses a mix of user space instrumentation and kernel APIs. ddprof runs in a separate process and processes events through shared ring buffers.

wrapper_architecture.png

IPC communication

Library communicates with profiler through a unix socket. Socket creation is the responsibility of the profiler. By default ddprof creates an random abstract socket, that does not exist on the filesystem: "\0/tmp/ddprof--<random_string>.sock" but unix socket path can be overridden with profiler --socket input option. Profiler worker process accepts and handles connections on this socket in a separate thread and sends ring buffer information upon request.

Overview of the communication process (wrapper mode):

  • Profiler starts, set DD_PROFILING_NATIVE_LIB_SOCKET env variable with socket path and daemonizes.
  • Target process starts and blocks on intermediate process termination
  • Profiler creates socket and listen on it, and then unblock target process by killing intermediate process.
  • Profiler forks into worker process and worker process starts accepting connections.
  • Library get socket path from DD_PROFILING_NATIVE_LIB_SOCKET, connects to it, retrieve ring buffer information and closes connection.
  • Exec'd processes from target process inherit DD_PROFILING_NATIVE_LIB_SOCKET env variable and connect to profiler in the same manner. Overview of the communication process (library mode):
  • Library starts, checks if DD_PROFILING_NATIVE_LIB_SOCKET is set.
  • If DD_PROFILING_NATIVE_LIB_SOCKET is set:
    • Library connects to socket, retrieve ring buffer information and closes connection.
  • Otherwise:
    • Library daemonizes into the profiler.
    • Profiler blocks on intermediate process termination.
    • Library unblocks profiler by killing intermediate process.
    • Library blocks on reading socket path from pipe created during daemonization.
    • Profiler starts, creates socket and listen on socket.
    • Profiler creates socket, listen on it and then sends socket path to library through pipe created during daemonization. Pipe allows library to retrieve socket path from profiler and to ensure that library tries to connect to socket after it has been created by profiler.
    • Library connects to socket, retrieve ring buffer information and closes connection.
    • Library sets environment variable DD_PROFILING_NATIVE_LIB_SOCKET with socket path so that socket is used by future exec'd processes.
    • Exec'd processes from target process inherit DD_PROFILING_NATIVE_LIB_SOCKET env variable and connect to profiler in the same manner as in wrapper mod