Spectator-js node.js metrics

⚠️ Experimental

Generate node.js internal metrics using the nflx-spectator node module.

Description

This module will generate node.js metrics using nflx-spectator.

Example

'use strict';

function getConfig() {
}

const spectator = require('nflx-spectator');
const NodeMetrics = require('nflx-spectator-nodejsmetrics');

const config = {
  commonTags: {'nf.node': 'i-1234'},
  uri: 'http://atlas.example.org/v1/publish'
};
const registry = new spectator.Registry(config);
registry.start();

const metrics = new NodeMetrics(registry);
metrics.start(); // start collecting nodejs metrics

// ...

metrics.stop();
registry.stop();

Metrics generated

Note that all metrics will have a nodejs.version tag

CPU

• nodejs.cpuUsage: Percentage of CPU time the node.js process is consuming [0, 100]:

  • id: user
  • id: system

  For example:

  {
      "tags": {
        "id": "system",
        "name": "nodejs.cpuUsage",
        /// nf.* tags
        "nodejs.version": "v6.5.0"
      },
      "start": 1485813720000,
      "value": 0.8954088417692685
    },
    {
      "tags": {
        "id": "user",
        "name": "nodejs.cpuUsage",
        /// nf.* tags
        "nodejs.version": "v6.5.0"
      },
      "start": 1485813720000,
      "value": 4.659007745141895
    }

Event Loop

• nodejs.eventLoop timer, which measures the time it takes for the event loop to complete. This is sampled twice per second.

• nodejs.eventLoopLag timer, which measures if the event loop is running behind by attempting to execute a timer once a second, and measuring the actual lag.

Garbage Collection Metrics

• nodejs.gc.allocationRate: measures in bytes/second how fast the app is allocating memory

• nodejs.gc.promotionRate: measures in bytes/second how fast data is being moved from new_space to old_space

• nodejs.gc.liveDataSize: measures in bytes the size of the old_space after a major GC event

• nodejs.gc.maxDataSize: measures the maximum amount of memory the nodejs process is allowed to use. Primarly used for gaining perspective on the liveDataSize.

• nodejs.gc.pause: times the time it takes for the different GC events:

  • id=scavenge: The most common garbage collection method. Node will typically trigger one of these every time the VM is idle.

  • id=markSweepCompact: The heaviest type of garbage collection V8 may do. If you see many of these happening you will need to either keep fewer objects around in your process or increase V8's heap limit

  • id=incrementalMarking: A phased garbage collection that interleaves collection with application logic to reduce the amount of time the application is paused.

  • id=processWeakCallbacks: After a garbage collection occurs, V8 will call any weak reference callbacks registered for objects that have been freed. This measurement is from the start of the first weak callback to the end of the last for a given garbage collection.

Memory Usage Metrics

Memory usage of the Node.js process in bytes:

• rss: nodejs.rss
• heapTotal: nodejs.heapTotal - v8 memory usage
• heapUsed: nodejs.heapUsed - v8 memory usage
• external: nodejs.external - memory usage of C++ objects bound to JS objects managed by v8

V8 Heap Statistics

• total_heap_size: nodejs.totalHeapSize

• total_heap_size_executable: nodejs.totalHeapSizeExecutable

• total_physical_size: nodejs.totalPhysicalSize

• total_available_size: nodejs.totalAvailableSize

• used_heap_size: nodejs.usedHeapSize

• heap_size_limit: nodejs.heapSizeLimit

• malloced_memory: nodejs.mallocedMemory

• peak_malloced_memory: nodejs.peakMallocedMemory

• does_zap_garbage: nodejs.doesZapGarbage - a 0/1 boolean, which signifies whether the --zap_code_space option is enabled or not. This makes V8 overwrite heap garbage with a bit pattern. The RSS footprint (resident memory set) gets bigger because it continuously touches all heap pages and that makes them less likely to get swapped out by the operating system.

V8 Heap Space Statistics

For each space returned by v8.getHeapSpaceStatistics

• space_size: nodejs.spaceSize id: <space_name>
• space_used_size: nodejs.spaceUsedSize id: <space_name>
• space_available_size: nodejs.spaceAvailableSize id: <space_name>
• physical_space_size: nodejs.physicalSpaceSize id: <space_name>

File descriptor usage

• Number currently opened: openFileDescriptorsCount

• Limit: maxFileDescriptorsCount - the maximum number of file descriptors we can have open at the same time.