1 files changed, 198 insertions, 0 deletions

diff --git a/server/lib/opentelemetry/metric-helpers/nodejs-observers-builder.ts b/server/lib/opentelemetry/metric-helpers/nodejs-observers-builder.ts
new file mode 100644
index 000000000..c51a50ebb
--- /dev/null
+++ b/server/lib/opentelemetry/metric-helpers/nodejs-observers-builder.ts
@@ -0,0 +1,198 @@
+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(async 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 ])
+  }
+}