event-loop-stats - npm Package Compare versions

Comparing version 1.2.0 to 1.3.0

CHANGELOG.md

 # Changelog
 
+## 1.3.0
+ - Detect synchronous blocks
+
 ## 1.2.0
@@ -4,0 +7,0 @@ - Support Node.js v12

package.json

 {
   "name": "event-loop-stats",
-  "version": "1.2.0",
+  "version": "1.3.0",
   "description": "Exposes stats about the libuv default loop",
@@ -5,0 +5,0 @@ "main": "src/eventLoopStats.js",

test/eventLoopStats.js

@@ -5,3 +5,2 @@ var eventLoopStats = require('..');
 describe('eventLoopStats', function() {
-
   it('should expose a sense function', function() {
@@ -27,2 +26,59 @@ expect(eventLoopStats.sense).to.be.a('function');
 
+  // This pattern will usually allow for at least _two_ on_check calls between
+  // the two sense calls. Check the next test for a slightly different pattern.
+  it('should detect a blocked event loop', function(done) {
+    // Call sense to reset max.
+    eventLoopStats.sense();
+    // On the next tick, block for 500ms.
+    setTimeout(function() {
+      var waitUntill = new Date(Date.now() + 500);
+      // Block event loop with busy waiting.
+      while (waitUntill > new Date()) {}
+
+      // On the next tick, detect stats again - the 500 ms block should have
+      // been noticed.
+      setTimeout(function() {
+        var stats = eventLoopStats.sense();
+        expect(stats.max).to.be.gte(490);
+        expect(stats.max).to.be.lt(2000);
+        expect(stats.sum).to.be.gte(490);
+        expect(stats.sum).to.be.lt(2000);
+
+        // At least two on_check calls should have happened (older Node.js versions will call it more often).
+        expect(stats.num).to.be.gte(2);
+
+        // Since there are at least two on_check calls, min and max should be different.
+        expect(stats.min).to.be.gte(0);
+        expect(stats.min).to.be.lt(stats.max);
+
+        done();
+      }, 0);
+    }, 0);
+  });
+
+  // This pattern will typically allow for only _one_ on_check call between the
+  // two sense calls (at least on more recent Node.js versions). Check the
+  // previous test for a slightly different pattern.
+  it('one on_check call should suffice to report correct max duration ', function(done) {
+    // Call sense to reset max.
+    eventLoopStats.sense();
+    var now = Date.now();
+    var end = now + 50;
+    setTimeout(function() {
+      // After 100ms, call sense again - the 50ms block (see below) should have been noticed.
+      var stats = eventLoopStats.sense();
+      expect(stats.max).to.be.gte(40);
+      expect(stats.max).to.be.lt(1000);
+      expect(stats.sum).to.be.gte(40);
+      expect(stats.sum).to.be.lt(1000);
+
+      // Only one on_check call might have happened.
+      expect(stats.num).to.gte(1);
+
+      done();
+    }, 100);
+
+    // Directly block for 50ms right in this tick, synchronously.
+    while (Date.now() < end) {}
+  });
 });

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Improved metrics

Total package byte prevSize

10206

increased by51.76%

Lines of code

86

increased by132.43%

No dependency changes