[quality] Possible Emitter memory leak detected when opening more than 15 editors

[kittaakos]

In my case, it was the Java editor:

Possible Emitter memory leak detected. 30 exit listeners added. Use event.maxListeners to increase limit
    at Emitter.../../packages/core/lib/common/event.js.Emitter.checkMaxListeners (http://localhost:3000/bundle.js:100299:26)
    at Proxy._event.Object.assign.maxListeners (http://localhost:3000/bundle.js:100266:27)
    at MonacoEditorProvider.<anonymous> (http://localhost:3000/26.bundle.js:686:63)
    at step (http://localhost:3000/26.bundle.js:540:23)
    at Object.next (http://localhost:3000/26.bundle.js:521:53)
    at fulfilled (http://localhost:3000/26.bundle.js:512:58)
log @ logger-protocol.ts:99
(anonymous) @ logger-frontend-module.ts:41
(anonymous) @ logger.ts:312
(anonymous) @ logger.ts:304
Promise.then (async)
../../packages/core/lib/common/logger.js.Logger.log @ logger.ts:299
log @ logger.ts:45
../../packages/core/lib/common/event.js.Emitter.checkMaxListeners @ event.ts:189
_event.Object.assign.maxListeners @ event.ts:155
(anonymous) @ monaco-editor-provider.js:213
step @ monaco-editor-provider.js:67
(anonymous) @ monaco-editor-provider.js:48
fulfilled @ monaco-editor-provider.js:39
Promise.then (async)
step @ monaco-editor-provider.js:41
(anonymous) @ monaco-editor-provider.js:42
push.../../packages/monaco/lib/browser/monaco-editor-provider.js.__awaiter @ monaco-editor-provider.js:38
push.../../packages/monaco/lib/browser/monaco-editor-provider.js.MonacoEditorProvider.createMonacoEditor @ monaco-editor-provider.js:203
push.../../packages/monaco/lib/browser/monaco-editor-provider.js.MonacoEditorProvider.createEditor @ monaco-editor-provider.js:193
(anonymous) @ monaco-editor-provider.js:155
(anonymous) @ monaco-editor-provider.js:170
step @ monaco-editor-provider.js:67
(anonymous) @ monaco-editor-provider.js:48
(anonymous) @ monaco-editor-provider.js:42
push.../../packages/monaco/lib/browser/monaco-editor-provider.js.__awaiter @ monaco-editor-provider.js:38
push.../../packages/monaco/lib/browser/monaco-editor-provider.js.MonacoEditorProvider.doCreateEditor @ monaco-editor-provider.js:161
(anonymous) @ monaco-editor-provider.js:155
step @ monaco-editor-provider.js:67
(anonymous) @ monaco-editor-provider.js:48
fulfilled @ monaco-editor-provider.js:39
Promise.then (async)
step @ monaco-editor-provider.js:41
(anonymous) @ monaco-editor-provider.js:42
push.../../packages/monaco/lib/browser/monaco-editor-provider.js.__awaiter @ monaco-editor-provider.js:38
push.../../packages/monaco/lib/browser/monaco-editor-provider.js.MonacoEditorProvider.get @ monaco-editor-provider.js:148
(anonymous) @ monaco-frontend-module.ts:76
(anonymous) @ editor-widget-factory.ts:47
step @ editor-widget-factory.ts:15
(anonymous) @ editor-widget-factory.ts:15
fulfilled @ editor-widget-factory.ts:15
Promise.then (async)
step @ editor-widget-factory.ts:15
(anonymous) @ editor-widget-factory.ts:15
push.../../packages/editor/lib/browser/editor-widget-factory.js.__awaiter @ editor-widget-factory.ts:15
push.../../packages/editor/lib/browser/editor-widget-factory.js.EditorWidgetFactory.createEditor @ editor-widget-factory.ts:45
push.../../packages/editor/lib/browser/editor-widget-factory.js.EditorWidgetFactory.createWidget @ editor-widget-factory.ts:42
(anonymous) @ widget-manager.ts:130
step @ widget-manager.ts:15
(anonymous) @ widget-manager.ts:15
fulfilled @ widget-manager.ts:15
Promise.then (async)
step @ widget-manager.ts:15
(anonymous) @ widget-manager.ts:15
../../packages/core/lib/browser/widget-manager.js.__awaiter @ widget-manager.ts:15
../../packages/core/lib/browser/widget-manager.js.WidgetManager.getOrCreateWidget @ widget-manager.ts:119
../../packages/core/lib/browser/widget-open-handler.js.WidgetOpenHandler.getOrCreateWidget @ widget-open-handler.ts:166
(anonymous) @ widget-open-handler.ts:83
step @ widget-open-handler.ts:15
(anonymous) @ widget-open-handler.ts:15
(anonymous) @ widget-open-handler.ts:15
../../packages/core/lib/browser/widget-open-handler.js.__awaiter @ widget-open-handler.ts:15
../../packages/core/lib/browser/widget-open-handler.js.WidgetOpenHandler.open @ widget-open-handler.ts:82
(anonymous) @ editor-manager.ts:104
step @ editor-manager.ts:15
(anonymous) @ editor-manager.ts:15
(anonymous) @ editor-manager.ts:15
push.../../packages/editor/lib/browser/editor-manager.js.__awaiter @ editor-manager.ts:15
push.../../packages/editor/lib/browser/editor-manager.js.EditorManager.open @ editor-manager.ts:103
(anonymous) @ typehierarchy-tree-widget.tsx:94
step @ typehierarchy-tree-widget.tsx:15
(anonymous) @ typehierarchy-tree-widget.tsx:15
(anonymous) @ typehierarchy-tree-widget.tsx:15
push.../../packages/typehierarchy/lib/browser/tree/typehierarchy-tree-widget.js.__awaiter @ typehierarchy-tree-widget.tsx:15
push.../../packages/typehierarchy/lib/browser/tree/typehierarchy-tree-widget.js.TypeHierarchyTreeWidget.openEditor @ typehierarchy-tree-widget.tsx:91
(anonymous) @ typehierarchy-tree-widget.tsx:53
../../packages/core/lib/common/event.js.CallbackList.invoke @ event.ts:107
../../packages/core/lib/common/event.js.Emitter.fire @ event.ts:199
../../packages/core/lib/browser/tree/tree-selection-impl.js.TreeSelectionServiceImpl.fireSelectionChanged @ tree-selection-impl.ts:50
../../packages/core/lib/browser/tree/tree-selection-impl.js.TreeSelectionServiceImpl.addSelection @ tree-selection-impl.ts:87
../../packages/core/lib/browser/tree/tree-model.js.TreeModelImpl.addSelection @ tree-model.ts:388
../../packages/core/lib/browser/tree/tree-model.js.TreeModelImpl.selectPrevNode @ tree-model.ts:267
../../packages/core/lib/browser/tree/tree-widget.js.TreeWidget.handleUp @ tree-widget.tsx:663
(anonymous) @ tree-widget.tsx:630
(anonymous) @ widget.ts:180

Also: https://github.com/theia-ide/yangster/issues/62

[lmcbout]

Could be related to issue #3023 as well. I also reproduce a memory leak with only one JAVA editor. I start theia, open a java file , then I stop and re-start the server. DO NOT REFRESH the client side. After ~15-30 sec, I see the memory leak on the server console and if I open a memroy tool (htop on ubuntu), i see the cpu is consuming 100% on all cores of my computer and remains like that for a long time. We see as well many java processes running . See picture below

[kittaakos]

I have added a dummy logging to the Java backend contribution, had the frontend running in the browser and restarted the backend. See how many times the backend tries to reconnect:

"3000"
root INFO [nsfw-watcher: 16577] Started watching: /Users/akos.kitta/git/theia/examples/browser/package.json
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Unregistering scopes for language: java.
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331203596/.metadata/.log
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331203675/.metadata/.log
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331203705/.metadata/.log
root INFO The scopes have been successfully unregistered for java.
root INFO Started watching the git repository: file:///Users/akos.kitta/git/eclipse.jdt.ls
root INFO Checking whether '--no-optional-locks' can be used with the current Git executable. Minimum required version is '2.15.0'.
root INFO [nsfw-watcher: 16578] Started watching: /Users/akos.kitta/.theia
root INFO Checking whether '--no-optional-locks' can be used with the current Git executable. Minimum required version is '2.15.0'.
root INFO [nsfw-watcher: 16578] Started watching: /Users/akos.kitta/git/eclipse.jdt.ls
root INFO Checking whether '--no-optional-locks' can be used with the current Git executable. Minimum required version is '2.15.0'.
root INFO [nsfw-watcher: 16578] Started watching: /Users/akos.kitta/git/eclipse.jdt.ls
root INFO '--no-optional-locks' is a valid Git option for the current Git version: '2.17.1'.
root INFO '--no-optional-locks' is a valid Git option for the current Git version: '2.17.1'.
root INFO [nsfw-watcher: 16578] Started watching: /Users/akos.kitta/git/eclipse.jdt.ls/org.eclipse.jdt.ls.core/src/org/eclipse/jdt/ls/core/internal/handlers/BundleUtils.java
root INFO '--no-optional-locks' is a valid Git option for the current Git version: '2.17.1'.
root INFO Registering scopes for language: java.
root INFO The scopes have been successfully registered for java.
root INFO Registering scopes for language: java.
root ERROR The scopes are already registered for language: java.
root INFO Registering scopes for language: java.
root ERROR The scopes are already registered for language: java.
root WARN A command java.edit.organizeImports is already registered.
root WARN A command java.edit.organizeImports is already registered.
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331254132/.metadata/.log
root WARN A command java.edit.organizeImports is already registered.
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331259199/.metadata/.log
root INFO Registering scopes for language: java.
root ERROR The scopes are already registered for language: java.
root INFO Registering scopes for language: java.
root ERROR The scopes are already registered for language: java.
root WARN A command java.edit.organizeImports is already registered.
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331269473/.metadata/.log
root WARN A command java.edit.organizeImports is already registered.
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331275000/.metadata/.log
root INFO Registering scopes for language: java.
root ERROR The scopes are already registered for language: java.
root INFO Registering scopes for language: java.
root ERROR The scopes are already registered for language: java.
root WARN A command java.edit.organizeImports is already registered.
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331284115/.metadata/.log
root WARN A command java.edit.organizeImports is already registered.
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331289170/.metadata/.log
root INFO Registering scopes for language: java.
root ERROR The scopes are already registered for language: java.
root INFO Registering scopes for language: java.
root ERROR The scopes are already registered for language: java.
root WARN A command java.edit.organizeImports is already registered.
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331299830/.metadata/.log
root WARN A command java.edit.organizeImports is already registered.
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331304305/.metadata/.log
root INFO Registering scopes for language: java.
root ERROR The scopes are already registered for language: java.
root INFO Registering scopes for language: java.
root ERROR The scopes are already registered for language: java.
root WARN A command java.edit.organizeImports is already registered.
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331311244/.metadata/.log
root WARN A command java.edit.organizeImports is already registered.
root INFO Registering scopes for language: java.
root ERROR The scopes are already registered for language: java.
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331316022/.metadata/.log
root INFO Registering scopes for language: java.
root ERROR The scopes are already registered for language: java.
root WARN A command java.edit.organizeImports is already registered.
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331323659/.metadata/.log
root WARN A command java.edit.organizeImports is already registered.
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331327191/.metadata/.log
root INFO Registering scopes for language: java.
root ERROR The scopes are already registered for language: java.
root INFO Registering scopes for language: java.
root ERROR The scopes are already registered for language: java.
root WARN A command java.edit.organizeImports is already registered.
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331335481/.metadata/.log
root WARN A command java.edit.organizeImports is already registered.
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331338907/.metadata/.log
root INFO Registering scopes for language: java.
root ERROR The scopes are already registered for language: java.
root INFO Registering scopes for language: java.
root ERROR The scopes are already registered for language: java.
root WARN A command java.edit.organizeImports is already registered.
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331348432/.metadata/.log
root INFO Registering scopes for language: java.
root ERROR The scopes are already registered for language: java.
root WARN A command java.edit.organizeImports is already registered.
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331358475/.metadata/.log
root WARN A command java.edit.organizeImports is already registered.
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331362507/.metadata/.log
root INFO Registering scopes for language: java.
root ERROR The scopes are already registered for language: java.
root INFO Registering scopes for language: java.
root ERROR The scopes are already registered for language: java.
root WARN A command java.edit.organizeImports is already registered.
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331372139/.metadata/.log
root WARN A command java.edit.organizeImports is already registered.
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331377059/.metadata/.log
root INFO Registering scopes for language: java.
root ERROR The scopes are already registered for language: java.
root INFO Registering scopes for language: java.
root ERROR The scopes are already registered for language: java.
root WARN A command java.edit.organizeImports is already registered.
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: logs at /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/_ws_1539331386633/.metadata/.log

And finally, we will hit the Possible Emitter memory leak detected. issue and the backend crash:

root INFO [nsfw-watcher: 18535] Started watching: /Users/akos.kitta/.theia
assert.js:42
  throw new errors.AssertionError({
  ^

AssertionError [ERR_ASSERTION]: false == true
    at RoundRobinHandle.add (internal/cluster/round_robin_handle.js:34:3)
    at queryServer (internal/cluster/master.js:316:10)
    at Worker.onmessage (internal/cluster/master.js:248:5)
    at ChildProcess.onInternalMessage (internal/cluster/utils.js:42:8)
    at emitTwo (events.js:131:20)
    at ChildProcess.emit (events.js:214:7)
    at emit (internal/child_process.js:772:12)
    at _combinedTickCallback (internal/process/next_tick.js:141:11)
    at process._tickCallback (internal/process/next_tick.js:180:9)
root INFO Java: HERE!!!!! starting the JDT LS
root INFO Java: HERE!!!!! starting the JDT LS

[tsmaeder]

@kittaakos related to the former java extension, I believe. Close?

[kittaakos]

Just open enough editors, any kind of them, and you will see the warning:

logger-protocol.ts:112 root WARN     at PreferenceServiceImpl._event.Object.assign.maxListeners [as onPreferencesChanged] (file:///Users/akos.kitta/git/theia/examples/electron/lib/bundle.js:134774:57)
    at Proxy.onPreferenceChanged (file:///Users/akos.kitta/git/theia/examples/electron/lib/bundle.js:114175:95)
    at MonacoTextModelService.<anonymous> (file:///Users/akos.kitta/git/theia/examples/electron/lib/16.bundle.js:925:61)
    at step (file:///Users/akos.kitta/git/theia/examples/electron/lib/16.bundle.js:831:23)
    at Object.next (file:///Users/akos.kitta/git/theia/examples/electron/lib/16.bundle.js:812:53

[kittaakos]

Possible related: https://github.com/eclipse-theia/theia/pull/13327 and https://github.com/eclipse-theia/theia/issues/13323

[msujew]

Given that this is related to the old (and long deprecated) java extension, we can close this.