3 |
4 | ## Installation
5 |
6 | ```
7 | npm install --save event-loop-stats
8 | ```
9 |
10 | ## Usage
11 | ```javascript
12 | var eventLoopStats = require('event-loop-stats');
13 | console.log('Stats', eventLoopStats.sense());
14 | ```
15 |
16 | This will print the following information:
17 |
18 | ```
19 | Stats {
20 | max: 5,
21 | min: 0,
22 | sum: 10,
23 | num: 5
24 | }
25 | ```
26 |
27 | ## Property insights
28 | - `max`: Maximum number of milliseconds spent in a single loop since last `sense call`.
29 | - `min`: Minimum number of milliseconds spent in a single loop since last `sense call`.
30 | - `sum`: Total number of milliseconds spent in the loop since last `sense call`.
31 | - `num`: Total number of loops since last `sense call`.
32 |
33 | ## Node version compatibility
34 | `event-loop-stats` depends on C++ extensions which are compiled when the `event-loop-stats` module is installed. Compatibility information can be inspected via the [Travis-CI build jobs](https://travis-ci.org/bripkens/event-loop-stats).
35 |
--------------------------------------------------------------------------------
/LICENSE:
--------------------------------------------------------------------------------
1 | The MIT License (MIT)
2 |
3 | Copyright (c) 2015-2022 Ben Blackmore and contributors
4 |
5 | Permission is hereby granted, free of charge, to any person obtaining a copy
6 | of this software and associated documentation files (the "Software"), to deal
7 | in the Software without restriction, including without limitation the rights
8 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
9 | copies of the Software, and to permit persons to whom the Software is
10 | furnished to do so, subject to the following conditions:
11 |
12 | The above copyright notice and this permission notice shall be included in
13 | all copies or substantial portions of the Software.
14 |
15 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
18 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
21 | THE SOFTWARE.
22 |
--------------------------------------------------------------------------------
/test/eventLoopStats.js:
--------------------------------------------------------------------------------
1 | var eventLoopStats = require('..');
2 | var expect = require('chai').expect;
3 |
4 | describe('eventLoopStats', function() {
5 | it('should expose a sense function', function() {
6 | expect(eventLoopStats.sense).to.be.a('function');
7 | });
8 |
9 | it('should return stats via the sense function', function(done) {
10 | setTimeout(function() {
11 | // provoke execution on the default loop
12 | }, 500);
13 |
14 | setTimeout(function() {
15 | var stats = eventLoopStats.sense();
16 | expect(stats.num).to.be.a('number');
17 | expect(stats.num).to.be.gt(0);
18 | expect(stats.sum).to.be.a('number');
19 | expect(stats.max).to.be.a('number');
20 | expect(stats.min).to.be.a('number');
21 | done();
22 | }, 1000);
23 | });
24 |
25 | // This pattern will usually allow for at least _two_ on_check calls between
26 | // the two sense calls. Check the next test for a slightly different pattern.
27 | it('should detect a blocked event loop', function(done) {
28 | // Call sense to reset max.
29 | eventLoopStats.sense();
30 | // On the next tick, block for 500ms.
31 | setTimeout(function() {
32 | var waitUntill = new Date(Date.now() + 500);
33 | // Block event loop with busy waiting.
34 | while (waitUntill > new Date()) {}
35 |
36 | // On the next tick, detect stats again - the 500 ms block should have
37 | // been noticed.
38 | setTimeout(function() {
39 | var stats = eventLoopStats.sense();
40 | expect(stats.max).to.be.gte(490);
41 | expect(stats.max).to.be.lt(2000);
42 | expect(stats.sum).to.be.gte(490);
43 | expect(stats.sum).to.be.lt(2000);
44 |
45 | // At least two on_check calls should have happened (older Node.js versions will call it more often).
46 | expect(stats.num).to.be.gte(2);
47 |
48 | // Since there are at least two on_check calls, min and max should be different.
49 | expect(stats.min).to.be.gte(0);
50 | expect(stats.min).to.be.lt(stats.max);
51 |
52 | done();
53 | }, 0);
54 | }, 0);
55 | });
56 |
57 | // This pattern will typically allow for only _one_ on_check call between the
58 | // two sense calls (at least on more recent Node.js versions). Check the
59 | // previous test for a slightly different pattern.
60 | it('one on_check call should suffice to report correct max duration ', function(done) {
61 | // Call sense to reset max.
62 | eventLoopStats.sense();
63 | var now = Date.now();
64 | var end = now + 50;
65 | setTimeout(function() {
66 | // After 100ms, call sense again - the 50ms block (see below) should have been noticed.
67 | var stats = eventLoopStats.sense();
68 | expect(stats.max).to.be.gte(40);
69 | expect(stats.max).to.be.lt(1000);
70 | expect(stats.sum).to.be.gte(40);
71 | expect(stats.sum).to.be.lt(1000);
72 |
73 | // Only one on_check call might have happened.
74 | expect(stats.num).to.gte(1);
75 |
76 | done();
77 | }, 100);
78 |
79 | // Directly block for 50ms right in this tick, synchronously.
80 | while (Date.now() < end) {}
81 | });
82 | });
83 |
--------------------------------------------------------------------------------
/src/eventLoopStats.cc:
--------------------------------------------------------------------------------
1 | #include
2 |
3 | using namespace v8;
4 |
5 | // Casting -1 to an uint will give the max uint value
6 | const uint32_t maxPossibleUint32 = -1;
7 | const uint64_t maxPossibleUint64 = -1;
8 | const uint32_t minPossibleUint32 = 0;
9 |
10 | uv_check_t check_handle;
11 |
12 | // The minimum event loop duration since the last sense() call.
13 | uint32_t min;
14 | // The maximum event loop duration since the last sense() call.
15 | uint32_t max;
16 | // The sum of event loop durations the last sense() call.
17 | uint32_t sum;
18 | // The number of event loop iterations since the last sense() call.
19 | uint32_t num;
20 |
21 | uint64_t previous_now = maxPossibleUint64;
22 |
23 | // This will be called after each sense call.
24 | void reset() {
25 | min = maxPossibleUint32;
26 | max = minPossibleUint32;
27 | sum = 0;
28 | num = 0;
29 | }
30 |
31 | // This will be called once per event loop iteration, right after polling
32 | // for i/o. See http://docs.libuv.org/en/v1.x/design.html#the-i-o-loop for a
33 | // general overview and http://docs.libuv.org/en/v1.x/check.html for details.
34 | void on_check(uv_check_t* handle) {
35 | // An earlier incarnation of event-loop-stats checked uv_hrtime() against
36 | // uv_now(handle->loop), which doesn't seem to work -- for example, it does
37 | // not detect long event loop iterations caused by a synchronous block due to
38 | // long running for- or while-loops. Checking against the time of the same
39 | // point at the last iteration of the event loop also covers these cases.
40 |
41 | const uint64_t now = uv_hrtime();
42 | uint32_t duration;
43 |
44 | if (previous_now >= now) {
45 | // This only happens on the very first call on_check call. Since we have no
46 | // timestamp to compare to from an earlier on_check call, we start by
47 | // assuming an event loop lag of zero.
48 | duration = 0;
49 | } else {
50 | // Calculate the duration since the last on_check call - this is the
51 | // event loop lag.
52 | // And convert to milliseconds (uv_hrtime yields nanos).
53 | duration = (now - previous_now) / static_cast(1e6);
54 | }
55 |
56 | // save min/max values
57 | if (duration < min) {
58 | min = duration;
59 | }
60 | if (duration > max) {
61 | max = duration;
62 | }
63 |
64 | // Sum up all durations between two consecutive sense() calls.
65 | sum += duration;
66 |
67 | // Simply count all event loop iterations between two sense() calls.
68 | num += 1;
69 |
70 | // Save the current timestamp for the next on_check call for comparison.
71 | previous_now = now;
72 | }
73 |
74 |
75 | static NAN_METHOD(sense) {
76 | // Reset min and max counters when there were no calls.
77 | if (num == 0) {
78 | min = 0;
79 | max = 0;
80 | }
81 |
82 | Local