perf_hooks: add warning when too many entries in the timeline

PR-URL: #18087
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

Author: jasnell

doc/api/perf_hooks.md

@@ -125,6 +125,20 @@ Creates a new `PerformanceMark` entry in the Performance Timeline. A
 `performanceEntry.duration` is always `0`. Performance marks are used
 to mark specific significant moments in the Performance Timeline.
 
+### performance.maxEntries
+<!-- YAML
+added: REPLACEME
+-->
+
+Value: {number}
+
+The maximum number of Performance Entry items that should be added to the
+Performance Timeline. This limit is not strictly enforced, but a process
+warning will be emitted if the number of entries in the timeline exceeds
+this limit.
+
+Defaults to 150.
+
 ### performance.measure(name, startMark, endMark)
 <!-- YAML
 added: v8.5.0

lib/perf_hooks.js

@@ -53,6 +53,9 @@ const kClearEntry = Symbol('clear-entry');
 constkGetEntries=Symbol('get-entries');
 constkIndex=Symbol('index');
 constkMarks=Symbol('marks');
+constkCount=Symbol('count');
+constkMaxCount=Symbol('max-count');
+constkDefaultMaxCount=150;
 
 observerCounts[NODE_PERFORMANCE_ENTRY_TYPE_MARK]=1;
 observerCounts[NODE_PERFORMANCE_ENTRY_TYPE_MEASURE]=1;
@@ -250,20 +253,32 @@ const nodeTiming = new PerformanceNodeTiming();
 // Maintains a list of entries as a linked list stored in insertion order.
 classPerformanceObserverEntryList{
 constructor(){
-Object.defineProperty(this,kEntries,{
-writable: true,
-enumerable: false,
-value: {}
+Object.defineProperties(this,{
+[kEntries]: {
+writable: true,
+enumerable: false,
+value: {}
+},
+[kCount]: {
+writable: true,
+enumerable: false,
+value: 0
+}
 });
 L.init(this[kEntries]);
 }
 
 [kInsertEntry](entry){
 constitem={ entry };
 L.append(this[kEntries],item);
+this[kCount]++;
 this[kIndexEntry](item);
 }
 
+getlength(){
+returnthis[kCount];
+}
+
 [kIndexEntry](entry){
 // Default implementation does nothing
 }
@@ -384,9 +399,22 @@ class Performance extends PerformanceObserverEntryList {
 this[kIndex]={
 [kMarks]: newSet()
 };
+this[kMaxCount]=kDefaultMaxCount;
 this[kInsertEntry](nodeTiming);
 }
 
+setmaxEntries(val){
+if(typeofval!=='number'||val>>>0!==val){
+consterrors=lazyErrors();
+thrownewerrors.TypeError('ERR_INVALID_ARG_TYPE','val','number');
+}
+this[kMaxCount]=Math.max(1,val>>>0);
+}
+
+getmaxEntries(){
+returnthis[kMaxCount];
+}
+
 [kIndexEntry](item){
 constindex=this[kIndex];
 consttype=item.entry.entryType;
@@ -397,6 +425,17 @@ class Performance extends PerformanceObserverEntryList {
 }
 constentry=item.entry;
 L.append(items,{ entry, item });
+constcount=this[kCount];
+if(count>this[kMaxCount]){
+consttext=count===1 ? 'is 1 entry' : `are ${count} entries`;
+process.emitWarning('Possible perf_hooks memory leak detected. '+
+`There ${text} in the `+
+'Performance Timeline. Use the clear methods '+
+'to remove entries that are no longer needed or '+
+'set performance.maxEntries equal to a higher '+
+'value (currently the maxEntries is '+
+`${this[kMaxCount]}).`);
+}
 }
 
 [kClearEntry](type,name){
@@ -411,10 +450,12 @@ class Performance extends PerformanceObserverEntryList {
 if(entry.name===`${name}`){
 L.remove(item);// remove from the index
 L.remove(item.item);// remove from the master
+this[kCount]--;
 }
 }else{
 L.remove(item);// remove from the index
 L.remove(item.item);// remove from the master
+this[kCount]--;
 }
 item=next;
 }

test/parallel/test-performance-warning.js

@@ -0,0 +1,29 @@
+// Flags: --no-warnings
+'use strict';
+
+constcommon=require('../common');
+const{ performance }=require('perf_hooks');
+constassert=require('assert');
+
+assert.strictEqual(performance.length,1);
+assert.strictEqual(performance.maxEntries,150);
+
+performance.maxEntries=1;
+
+[-1,0xffffffff+1,'',null,undefined,Infinity].forEach((i)=>{
+common.expectsError(
+()=>performance.maxEntries=i,
+{
+code: 'ERR_INVALID_ARG_TYPE',
+type: TypeError
+}
+);
+});
+
+common.expectWarning('Warning',[
+'Possible perf_hooks memory leak detected. There are 2 entries in the '+
+'Performance Timeline. Use the clear methods to remove entries that are no '+
+'longer needed or set performance.maxEntries equal to a higher value '+
+'(currently the maxEntries is 1).']);
+
+performance.mark('test');