fix(node-http-handler): call socket.setKeepAlive if enabled in http(s)Agent

packages/node-http-handler/src/node-http-handler.ts

@@ -9,6 +9,7 @@ import { getTransformedHeaders } from "./get-transformed-headers";
 import { setConnectionTimeout } from "./set-connection-timeout";
 import { setSocketTimeout } from "./set-socket-timeout";
 import { writeRequestBody } from "./write-request-body";
+import { setSocketKeepAlive, SocketKeepAliveOptions } from "./set-socket-keep-alive";
 
 /**
  * Represents the http options that can be passed to a node http client.
@@ -151,6 +152,16 @@ export class NodeHttpHandler implements HttpHandler {
         };
       }
 
+      const httpAgent = nodeHttpsOptions.agent;
+      if (typeof httpAgent === "object" && "keepAlive" in httpAgent) {
+        setSocketKeepAlive(req, {
+          // @ts-expect-error keepAlive is not public on httpAgent.
+          keepAlive: (httpAgent as hAgent).keepAlive,
+          // @ts-expect-error keepAliveMsecs is not public on httpAgent.
+          keepAliveMsecs: (httpAgent as hAgent).keepAliveMsecs,
+        });
+      }
+
       writeRequestBody(req, request);
     });
   }

packages/node-http-handler/src/set-socket-keep-alive.spec.ts

@@ -0,0 +1,66 @@
+import { setSocketKeepAlive } from "./set-socket-keep-alive";
+import { EventEmitter } from "events";
+
+class MockSocket {
+  enableKeepAlive: boolean;
+  keepAliveInitialDelay: number;
+
+  setKeepAlive(enable, initialDelay) {
+    this.enableKeepAlive = enable;
+    this.keepAliveInitialDelay = initialDelay;
+  }
+
+  isKeepAliveEnabled() {
+    return this.enableKeepAlive;
+  }
+
+  getKeepALiveInitialDelay() {
+    return this.keepAliveInitialDelay;
+  }
+}
+
+describe("setSocketKeepAlive", () => {
+  let request: any;
+  let socket;
+
+  beforeEach(() => {
+    request = new EventEmitter();
+    socket = new MockSocket();
+  });
+
+  it("should set keepAlive to true", () => {
+    setSocketKeepAlive(request, {
+      keepAlive: true,
+    });
+    request.emit("socket", socket);
+
+    expect(socket.isKeepAliveEnabled()).toBeTruthy();
+  });
+
+  it("should set keepAlive to true with custom initialDelay", () => {
+    const initialDelay = 5 * 1000;
+    setSocketKeepAlive(request, {
+      keepAlive: true,
+      keepAliveMsecs: initialDelay,
+    });
+    request.emit("socket", socket);
+
+    expect(socket.isKeepAliveEnabled() && socket.getKeepALiveInitialDelay() === initialDelay).toBeTruthy();
+  });
+
+  it("should not set keepAlive at all when keepAlive is false", () => {
+    setSocketKeepAlive(request, {
+      keepAlive: false,
+    });
+    request.emit("socket", socket);
+
+    expect(socket.isKeepAliveEnabled()).toBeFalsy();
+  });
+
+  it("should not set keepAlive at all when socketKeepAlive is undefined", () => {
+    setSocketKeepAlive(request, undefined);
+    request.emit("socket", socket);
+
+    expect(socket.isKeepAliveEnabled()).toBeFalsy();
+  });
+});

packages/node-http-handler/src/set-socket-keep-alive.ts

@@ -0,0 +1,16 @@
+import { ClientRequest } from "http";
+
+export interface SocketKeepAliveOptions {
+  keepAlive: boolean;
+  keepAliveMsecs?: number;
+}
+
+export const setSocketKeepAlive = (request: ClientRequest, socketKeepAlive: SocketKeepAliveOptions) => {
+  if (socketKeepAlive?.keepAlive !== true) {
+    return;
+  }
+
+  request.on("socket", (socket) => {
+    socket.setKeepAlive(socketKeepAlive.keepAlive, socketKeepAlive.keepAliveMsecs || 0);
+  });
+};