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import { readdir } from 'fs-extra'
import { constants, PerformanceObserver } from 'perf_hooks'
import * as process from 'process'
import { Meter, ObservableResult } from '@opentelemetry/api-metrics'
import { ExplicitBucketHistogramAggregation, MeterProvider } from '@opentelemetry/sdk-metrics-base'
import { View } from '@opentelemetry/sdk-metrics-base/build/src/view/View'
import { logger } from '@server/helpers/logger'
// Thanks to https://github.com/siimon/prom-client
// We took their logic and adapter it for opentelemetry
// Try to keep consistency with their metric name/description so it's easier to process (grafana dashboard template etc)
export class NodeJSObserversBuilder {
constructor (private readonly meter: Meter, private readonly meterProvider: MeterProvider) {
}
buildObservers () {
this.buildCPUObserver()
this.buildMemoryObserver()
this.buildHandlesObserver()
this.buildFileDescriptorsObserver()
this.buildGCObserver()
this.buildEventLoopLagObserver()
this.buildLibUVActiveRequestsObserver()
this.buildActiveResourcesObserver()
}
private buildCPUObserver () {
const cpuTotal = this.meter.createObservableCounter('process_cpu_seconds_total', {
description: 'Total user and system CPU time spent in seconds.'
})
const cpuUser = this.meter.createObservableCounter('process_cpu_user_seconds_total', {
description: 'Total user CPU time spent in seconds.'
})
const cpuSystem = this.meter.createObservableCounter('process_cpu_system_seconds_total', {
description: 'Total system CPU time spent in seconds.'
})
let lastCpuUsage = process.cpuUsage()
this.meter.addBatchObservableCallback(observableResult => {
const cpuUsage = process.cpuUsage()
const userUsageMicros = cpuUsage.user - lastCpuUsage.user
const systemUsageMicros = cpuUsage.system - lastCpuUsage.system
lastCpuUsage = cpuUsage
observableResult.observe(cpuTotal, (userUsageMicros + systemUsageMicros) / 1e6)
observableResult.observe(cpuUser, userUsageMicros / 1e6)
observableResult.observe(cpuSystem, systemUsageMicros / 1e6)
}, [ cpuTotal, cpuUser, cpuSystem ])
}
private buildMemoryObserver () {
this.meter.createObservableGauge('nodejs_memory_usage_bytes', {
description: 'Memory'
}).addCallback(observableResult => {
const current = process.memoryUsage()
observableResult.observe(current.heapTotal, { memoryType: 'heapTotal' })
observableResult.observe(current.heapUsed, { memoryType: 'heapUsed' })
observableResult.observe(current.arrayBuffers, { memoryType: 'arrayBuffers' })
observableResult.observe(current.external, { memoryType: 'external' })
observableResult.observe(current.rss, { memoryType: 'rss' })
})
}
private buildHandlesObserver () {
if (typeof (process as any)._getActiveHandles !== 'function') return
this.meter.createObservableGauge('nodejs_active_handles_total', {
description: 'Total number of active handles.'
}).addCallback(observableResult => {
const handles = (process as any)._getActiveHandles()
observableResult.observe(handles.length)
})
}
private buildGCObserver () {
const kinds = {
[constants.NODE_PERFORMANCE_GC_MAJOR]: 'major',
[constants.NODE_PERFORMANCE_GC_MINOR]: 'minor',
[constants.NODE_PERFORMANCE_GC_INCREMENTAL]: 'incremental',
[constants.NODE_PERFORMANCE_GC_WEAKCB]: 'weakcb'
}
this.meterProvider.addView(
new View({ aggregation: new ExplicitBucketHistogramAggregation([ 0.001, 0.01, 0.1, 1, 2, 5 ]) }),
{ instrument: { name: 'nodejs_gc_duration_seconds' } }
)
const histogram = this.meter.createHistogram('nodejs_gc_duration_seconds', {
description: 'Garbage collection duration by kind, one of major, minor, incremental or weakcb'
})
const obs = new PerformanceObserver(list => {
const entry = list.getEntries()[0]
// Node < 16 uses entry.kind
// Node >= 16 uses entry.detail.kind
// See: https://nodejs.org/docs/latest-v16.x/api/deprecations.html#deprecations_dep0152_extension_performanceentry_properties
const kind = (entry as any).detail
? kinds[(entry as any).detail.kind]
: kinds[entry.kind]
// Convert duration from milliseconds to seconds
histogram.record(entry.duration / 1000, {
kind
})
})
obs.observe({ entryTypes: [ 'gc' ] })
}
private buildEventLoopLagObserver () {
const reportEventloopLag = (start: [ number, number ], observableResult: ObservableResult, res: () => void) => {
const delta = process.hrtime(start)
const nanosec = delta[0] * 1e9 + delta[1]
const seconds = nanosec / 1e9
observableResult.observe(seconds)
res()
}
this.meter.createObservableGauge('nodejs_eventloop_lag_seconds', {
description: 'Lag of event loop in seconds.'
}).addCallback(observableResult => {
return new Promise(res => {
const start = process.hrtime()
setImmediate(reportEventloopLag, start, observableResult, res)
})
})
}
private buildFileDescriptorsObserver () {
this.meter.createObservableGauge('process_open_fds', {
description: 'Number of open file descriptors.'
}).addCallback(async observableResult => {
try {
const fds = await readdir('/proc/self/fd')
observableResult.observe(fds.length - 1)
} catch (err) {
logger.debug('Cannot list file descriptors of current process for OpenTelemetry.', { err })
}
})
}
private buildLibUVActiveRequestsObserver () {
if (typeof (process as any)._getActiveRequests !== 'function') return
this.meter.createObservableGauge('nodejs_active_requests_total', {
description: 'Total number of active libuv requests.'
}).addCallback(observableResult => {
const requests = (process as any)._getActiveRequests()
observableResult.observe(requests.length)
})
}
private buildActiveResourcesObserver () {
if (typeof (process as any).getActiveResourcesInfo !== 'function') return
const grouped = this.meter.createObservableCounter('nodejs_active_resources', {
description: 'Number of active resources that are currently keeping the event loop alive, grouped by async resource type.'
})
const total = this.meter.createObservableCounter('nodejs_active_resources_total', {
description: 'Total number of active resources.'
})
this.meter.addBatchObservableCallback(observableResult => {
const resources = (process as any).getActiveResourcesInfo()
const data = {}
for (let i = 0; i < resources.length; i++) {
const resource = resources[i]
if (data[resource] === undefined) data[resource] = 0
data[resource] += 1
}
for (const type of Object.keys(data)) {
observableResult.observe(grouped, data[type], { type })
}
observableResult.observe(total, resources.length)
}, [ grouped, total ])
}
}
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