Avoid restarting profiling for last collect

Upon process exit, profiler collects profiles a last time and was
restarting all profilers before stopping them.
Avoid this useless restart by changing the profiler API and make
`profile()` methode take a restart argument.

Author: nsavoire

packages/dd-trace/src/profiling/profiler.js

@@ -69,7 +69,7 @@ class Profiler extends EventEmitter {
           mapper,
           nearOOMCallback: this._nearOOMExport.bind(this)
         })
-        this._logger.debug(`Started ${profiler.type} profiler in thread ${threadId}`)
+        this._logger.debug(`Started ${profiler.type} profiler in ${threadNamePrefix} thread`)
       }
 
       this._capture(this._timeoutInterval, start)
@@ -98,7 +98,7 @@ class Profiler extends EventEmitter {
 
     // collect and export current profiles
     // once collect returns, profilers can be safely stopped
-    this._collect(snapshotKinds.ON_SHUTDOWN)
+    this._collect(snapshotKinds.ON_SHUTDOWN, false)
     this._stop()
   }
 
@@ -109,13 +109,11 @@ class Profiler extends EventEmitter {
 
     for (const profiler of this._config.profilers) {
       profiler.stop()
-      this._logger.debug(`Stopped ${profiler.type} profiler`)
+      this._logger.debug(`Stopped ${profiler.type} profiler in ${threadNamePrefix} thread`)
     }
 
     clearTimeout(this._timer)
     this._timer = undefined
-
-    return this
   }
 
   _capture (timeout, start) {
@@ -129,18 +127,21 @@ class Profiler extends EventEmitter {
     }
   }
 
-  async _collect (snapshotKind) {
+  async _collect (snapshotKind, restart = true) {
     if (!this._enabled) return
 
-    const start = this._lastStart
-    const end = new Date()
+    const startDate = this._lastStart
+    const endDate = new Date()
     const profiles = []
     const encodedProfiles = {}
 
     try {
       // collect profiles synchronously so that profilers can be safely stopped asynchronously
       for (const profiler of this._config.profilers) {
-        const profile = profiler.profile(start, end)
+        const profile = profiler.profile({ startDate, endDate, restart })
+        if (!restart) {
+          this._logger.debug(`Stopped ${profiler.type} profiler in ${threadNamePrefix} thread`)
+        }
         if (!profile) continue
         profiles.push({ profiler, profile })
       }
@@ -156,8 +157,10 @@ class Profiler extends EventEmitter {
         })
       }
 
-      this._capture(this._timeoutInterval, end)
-      await this._submit(encodedProfiles, start, end, snapshotKind)
+      if (restart) {
+        this._capture(this._timeoutInterval, endDate)
+      }
+      await this._submit(encodedProfiles, startDate, endDate, snapshotKind)
       this._logger.debug('Submitted profiles')
     } catch (err) {
       this._logger.error(err)
@@ -197,10 +200,10 @@ class ServerlessProfiler extends Profiler {
     this._flushAfterIntervals = this._config.flushInterval / 1000
   }
 
-  async _collect (snapshotKind) {
-    if (this._profiledIntervals >= this._flushAfterIntervals) {
+  async _collect (snapshotKind, restart = true) {
+    if (this._profiledIntervals >= this._flushAfterIntervals || !restart) {
       this._profiledIntervals = 0
-      await super._collect(snapshotKind)
+      await super._collect(snapshotKind, restart)
     } else {
       this._profiledIntervals += 1
       this._capture(this._timeoutInterval, new Date())

packages/dd-trace/src/profiling/profilers/events.js

@@ -171,10 +171,11 @@ class EventsProfiler {
   stop () {
     if (this._observer) {
       this._observer.disconnect()
+      this._observer = undefined
     }
   }
 
-  profile (startDate, endDate) {
+  profile ({ startDate, endDate, restart = true }) {
     if (this.entries.length === 0) {
       // No events in the period; don't produce a profile
       return null
@@ -243,6 +244,10 @@ class EventsProfiler {
       unit: stringTable.dedup(pprofValueUnit)
     })
 
+    if (!restart) {
+      this.stop()
+    }
+
     return new Profile({
       sampleType: [timeValueType],
       timeNanos: endDate.getTime() * MS_TO_NS,

packages/dd-trace/src/profiling/profilers/space.js

@@ -33,8 +33,12 @@ class NativeSpaceProfiler {
     }
   }
 
-  profile () {
-    return this._pprof.heap.profile(undefined, this._mapper, getThreadLabels)
+  profile ({ restart = true } = {}) {
+    const profile = this._pprof.heap.profile(undefined, this._mapper, getThreadLabels)
+    if (!restart) {
+      this.stop()
+    }
+    return profile
   }
 
   encode (profile) {

packages/dd-trace/src/profiling/profilers/wall.js

@@ -223,18 +223,32 @@ class NativeWallProfiler {
 
   _stop (restart) {
     if (!this._started) return
+
     if (this._captureSpanData) {
       // update last sample context if needed
       this._enter()
       this._lastSampleCount = 0
     }
     const profile = this._pprof.time.stop(restart, this._generateLabels)
+
     if (restart) {
       const v8BugDetected = this._pprof.time.v8ProfilerStuckEventLoopDetected()
       if (v8BugDetected !== 0) {
         this._reportV8bug(v8BugDetected === 1)
       }
+    } else {
+      if (this._captureSpanData) {
+        beforeCh.unsubscribe(this._enter)
+        enterCh.unsubscribe(this._enter)
+        spanFinishCh.unsubscribe(this._spanFinished)
+        this._profilerState = undefined
+        this._lastSpan = undefined
+        this._lastStartedSpans = undefined
+        this._lastWebTags = undefined
+      }
+      this._started = false
     }
+
     return profile
   }
 
@@ -276,30 +290,16 @@ class NativeWallProfiler {
     return labels
   }
 
-  profile () {
-    return this._stop(true)
+  profile ({ restart = true } = {}) {
+    return this._stop(restart)
   }
 
   encode (profile) {
     return this._pprof.encode(profile)
   }
 
   stop () {
-    if (!this._started) return
-
-    const profile = this._stop(false)
-    if (this._captureSpanData) {
-      beforeCh.unsubscribe(this._enter)
-      enterCh.unsubscribe(this._enter)
-      spanFinishCh.unsubscribe(this._spanFinished)
-      this._profilerState = undefined
-      this._lastSpan = undefined
-      this._lastStartedSpans = undefined
-      this._lastWebTags = undefined
-    }
-
-    this._started = false
-    return profile
+    this._stop(false)
   }
 }