fix: clean up old requests to prevent lambda resource exhaustion (#1217)

refs PR 1210

Author: aryamohanan

packages/serverless/src/backend_connector.js

@@ -308,6 +308,9 @@ function send(resourcePath, payload, finalLambdaRequest, callback) {
       if (finalLambdaRequest) {
         req.removeAllListeners();
         req.on('error', () => {});
+        // At this point we already received a response from the server, but since we removed all listeners we have to
+        // manually clean up the request.
+        req.destroy();
       }
 
       handleCallback();

packages/serverless/test/backend_connector_test.js

@@ -32,18 +32,21 @@ describe('[UNIT] backend connector', () => {
     this.timeout(config.getTestTimeout());
 
     let onStub;
+    let destroyStub;
 
     beforeEach(() => {
       sinon.spy(global, 'setInterval');
       sinon.spy(global, 'clearInterval');
 
       onStub = sinon.stub();
+      destroyStub = sinon.stub();
 
       sinon.stub(uninstrumentedHttp.http, 'request').returns({
         on: onStub,
         setTimeout: sinon.stub(),
         end: sinon.stub(),
-        removeAllListeners: sinon.stub()
+        removeAllListeners: sinon.stub(),
+        destroy: destroyStub
       });
     });
 
@@ -97,6 +100,8 @@ describe('[UNIT] backend connector', () => {
 
         setTimeout(onEnd, 200);
         await prom;
+
+        expect(destroyStub.called).to.be.true;
       });
     });
 
@@ -122,6 +127,8 @@ describe('[UNIT] backend connector', () => {
 
         setTimeout(onEnd, 200);
         await prom;
+
+        expect(destroyStub.called).to.be.true;
       });
     });
 
@@ -163,6 +170,8 @@ describe('[UNIT] backend connector', () => {
 
         // 1 bundle req, 2 heartbeats
         expect(uninstrumentedHttp.http.request.callCount).to.eql(3);
+
+        expect(destroyStub.called).to.be.true;
       });
     });
 
@@ -224,6 +233,8 @@ describe('[UNIT] backend connector', () => {
         await delay(250);
 
         expect(uninstrumentedHttp.http.request.callCount).to.eql(2);
+
+        expect(destroyStub.called).to.be.true;
       });
     });
   });