fix(leak): HTTP agents with maxSockets: Infinity result in a large me…

…mory leak

This memory leak cannot be truly fixed, as Node.js itself is keeping
these sockets alive. cls-hooked context objects will therefore continue
to exist as long as the socket hasn't been closed.

We can only reduce the impact this has on a monitored system and the
likeliness that this turns into a problem, by removing (potentially)
large span objects from the CLS context objects.

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
  - Prepare support for 128bit trace IDs.
+ - Reduce memory footprint when using HTTP agents with `maxSockets: Infinity`.
 
 ## 1.37.2
  - MongoDB: Properly initialize and assure operationId is generated

package.json

@@ -39,9 +39,10 @@
  },
  "homepage": "https://github.com/instana/nodejs-sensor#readme",
  "dependencies": {
+ "async-hook-jl": "^1.7.6",
  "bunyan": "^1.5.1",
  "cls-bluebird": "^2.1.0",
- "cls-hooked": "4.2.2",
+ "emitter-listener": "^1.1.1",
  "event-loop-lag": "^1.3.0",
  "opentracing": "^0.14.1",
  "redis-commands": "^1.3.1",

src/tracing/cls.js

@@ -1,10 +1,12 @@
 'use strict';
 
+var transmission = require('./transmission');
 var tracingUtil = require('./tracingUtil');
-var hooked = require('cls-hooked');
+var hooked = require('./clsHooked');
 
-var currentRootSpanKey = 'com.instana.rootSpan';
-var currentSpanKey = 'com.instana.span';
+var currentRootSpanKey = exports.currentRootSpanKey = 'com.instana.rootSpan';
+var currentSpanKey = exports.currentSpanKey = 'com.instana.span';
+var tracingLevelKey = exports.tracingLevelKey = 'com.instana.tl';
 
 var exitSpans = ['node.http.client', 'elasticsearch', 'mongo', 'mysql', 'redis'];
 var entrySpans = ['node.http.server'];
@@ -18,30 +20,15 @@ var entrySpans = ['node.http.server'];
  * cls.ns.run(function() {});
  *
  */
-var instanaNamespace = 'instana.sensor';
-Object.defineProperty(exports, 'ns', {
- get: function() {
- return hooked.getNamespace(instanaNamespace) || hooked.createNamespace(instanaNamespace);
- }
-});
+exports.ns = hooked.createNamespace('instana.sensor');
 
 /*
  * Start a new span and set it as the current span
  *
  */
-exports.startSpan = function startSpan(spanName, traceId, spanId) {
- var span = {
- f: tracingUtil.getFrom(),
- async: false,
- error: false,
- ec: 0,
- ts: Date.now(),
- d: 0,
- n: spanName,
- stack: [],
- data: null
- };
-
+exports.startSpan = function startSpan(spanName, traceId, spanId, modifyAsyncContext) {
+ modifyAsyncContext = modifyAsyncContext !== false;
+ var span = new InstanaSpan(spanName);
  var parentSpan = exports.ns.get(currentSpanKey);
 
  // If specified, use params
@@ -61,14 +48,19 @@ exports.startSpan = function startSpan(spanName, traceId, spanId) {
  // Set span direction type (1=entry, 2=exit, 3=local/intermediate)
  if (entrySpans.indexOf(span.n) > -1) {
  span.k = 1;
- exports.ns.set(currentRootSpanKey, span);
+
+ if (!span.p && modifyAsyncContext) {
+ span.addCleanup(exports.ns.set(currentRootSpanKey, span));
+ }
  } else if (exitSpans.indexOf(span.n) > -1) {
  span.k = 2;
  } else {
  span.k = 3;
  }
 
- exports.ns.set(currentSpanKey, span);
+ if (modifyAsyncContext) {
+ span.addCleanup(exports.ns.set(currentSpanKey, span));
+ }
  return span;
 };
 
@@ -85,7 +77,8 @@ exports.getCurrentRootSpan = function getCurrentRootSpan() {
  *
  */
 exports.setCurrentSpan = function setCurrentSpan(span) {
- return exports.ns.set(currentSpanKey, span);
+ exports.ns.set(currentSpanKey, span);
+ return span;
 };
 
 /*
@@ -107,9 +100,9 @@ exports.isTracing = function isTracing() {
 /*
  * Set the tracing level
  */
-var tracingLevelKey = 'tlKey';
 exports.setTracingLevel = function setTracingLevel(level) {
- return exports.ns.set(tracingLevelKey, level);
+ exports.ns.set(tracingLevelKey, level);
+ return level;
 };
 
 /*
@@ -154,3 +147,55 @@ exports.isExitSpan = function isExitSpan(span) {
 exports.isLocalSpan = function isLocalSpan(span) {
  return span.k === 3 ? true : false;
 };
+
+/*
+ * Instead of creating a span object via {}, we use new InstanaSpan().
+ * This will support better debugging, especially in cases where we need
+ * to analyse heap dumps.
+ *
+ * Furthermore, it allows us to add CLS cleanup logic to the span and to
+ * manipulate JSON serialization logic.
+ */
+function InstanaSpan(name) {
+ // properties that part of our span model
+ this.t = undefined;
+ this.s = undefined;
+ this.p = undefined;
+ this.k = undefined;
+ this.n = name;
+ this.f = tracingUtil.getFrom();
+ this.async = false;
+ this.error = false;
+ this.ec = 0;
+ this.ts = Date.now();
+ this.d = 0;
+ this.stack = [];
+ this.data = undefined;
+
+ // properties used within the sensor that should not be transmitted to the agent/backend
+ // NOTE: If you add a new property, make sure that it is not enumerable, as it may otherwise be transmitted
+ // to the backend!
+ Object.defineProperty(this, 'cleanupFunctions', {
+ value: [],
+ writable: false,
+ enumerable: false
+ });
+}
+
+InstanaSpan.prototype.addCleanup = function addCleanup(fn) {
+ this.cleanupFunctions.push(fn);
+};
+
+InstanaSpan.prototype.transmit = function transmit() {
+ transmission.addSpan(this);
+ this.cleanup();
+};
+
+InstanaSpan.prototype.cleanup = function cleanup() {
+ this.cleanupFunctions.forEach(call);
+ this.cleanupFunctions.length = 0;
+};
+
+function call(fn) {
+ fn();
+}