Added spec for k-NN warmup api

model/knn/warmup/operations.smithy

@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: Apache-2.0
+//
+//  The OpenSearch Contributors require contributions made to
+//  this file be licensed under the Apache-2.0 license or a
+//  compatible open source license.
+
+$version: "2"
+namespace OpenSearch
+
+@externalDocumentation(
+    "API Reference": "https://opensearch.org/docs/latest/search-plugins/knn/api/#warmup-operation"
+)
+
+@xOperationGroup("knn.warmup")
+@xVersionAdded("1.0")
+@readonly
+@suppress(["HttpUriConflict"])
+@http(method: "GET", uri: "/_plugins/_knn/warmup/{index}")
+@documentation("Preloads native library files into memory, reducing initial search latency for specified indexes")
+operation KNNWarmup {
+    input: KNNWarmup_Input,
+    output: KNNWarmup_Output
+}

model/knn/warmup/structures.smithy

@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: Apache-2.0
+//
+//  The OpenSearch Contributors require contributions made to
+//  this file be licensed under the Apache-2.0 license or a
+//  compatible open source license.
+
+$version: "2"
+namespace OpenSearch
+
+@input
+structure KNNWarmup_Input {
+    @required
+    @httpLabel
+    index: PathIndices,
+}
+
+// TODO: Fill in Output Structure
+structure KNNWarmup_Output{}

model/opensearch.smithy

@@ -262,6 +262,7 @@ service OpenSearch {
         KNNSearchModels_Post,
         KNNTrainModel,
         KNNTrainModel_WithModelId,
+        KNNWarmup,
         Mget_Get,
         Mget_Get_WithIndex,
         Mget_Post,