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It appears that in some cases, LSP4E can block the UI thread while waiting on a response from the language server. Example stack trace: !ENTRY org.eclipse.lsp4e 4 0 2018-07-07 20:38:10.751 !MESSAGE LanguageServer not initialized after 10s !STACK 0 java.util.concurrent.TimeoutException at java.util.concurrent.CompletableFuture.timedGet(CompletableFuture.java:1771) at java.util.concurrent.CompletableFuture.get(CompletableFuture.java:1915) at org.eclipse.lsp4e.LanguageServerWrapper.getServerCapabilities(LanguageServerWrapper.java:558) at org.eclipse.lsp4e.LanguageServiceAccessor.lambda$8(LanguageServiceAccessor.java:368) at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:174) at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:175) at java.util.HashMap$KeySpliterator.forEachRemaining(HashMap.java:1553) at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481) at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471) at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708) at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499) at org.eclipse.lsp4e.LanguageServiceAccessor.getMatchingStartedWrappers(LanguageServiceAccessor.java:370) at org.eclipse.lsp4e.LanguageServiceAccessor.getLSWrappers(LanguageServiceAccessor.java:280) at org.eclipse.lsp4e.LanguageServiceAccessor.getLSPDocumentInfosFor(LanguageServiceAccessor.java:433) at org.eclipse.lsp4e.operations.rename.LSPRenameHandler.isEnabled(LSPRenameHandler.java:73) at org.eclipse.ui.internal.handlers.HandlerProxy.isEnabled(HandlerProxy.java:308) at org.eclipse.ui.internal.handlers.E4HandlerProxy.canExecute(E4HandlerProxy.java:73) at sun.reflect.GeneratedMethodAccessor2.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.eclipse.e4.core.internal.di.MethodRequestor.execute(MethodRequestor.java:55) at org.eclipse.e4.core.internal.di.InjectorImpl.invokeUsingClass(InjectorImpl.java:318) at org.eclipse.e4.core.internal.di.InjectorImpl.invoke(InjectorImpl.java:252) at org.eclipse.e4.core.contexts.ContextInjectionFactory.invoke(ContextInjectionFactory.java:161) at org.eclipse.e4.core.commands.internal.HandlerServiceHandler.isEnabled(HandlerServiceHandler.java:58) at org.eclipse.core.commands.Command.isEnabled(Command.java:838) at org.eclipse.e4.core.commands.internal.HandlerServiceImpl.canExecute(HandlerServiceImpl.java:177) at org.eclipse.e4.ui.workbench.renderers.swt.MenuManagerRendererFilter.updateElementVisibility(MenuManagerRendererFilter.java:220) at org.eclipse.e4.ui.workbench.renderers.swt.MenuManagerShowProcessor.showMenu(MenuManagerShowProcessor.java:255) at org.eclipse.e4.ui.workbench.renderers.swt.MenuManagerShowProcessor.menuAboutToHide(MenuManagerShowProcessor.java:112) at org.eclipse.jface.internal.MenuManagerEventHelper.showEventPostHelper(MenuManagerEventHelper.java:92) at org.eclipse.jface.action.MenuManager.handleAboutToShow(MenuManager.java:471) at org.eclipse.jface.action.MenuManager.access$1(MenuManager.java:465) at org.eclipse.jface.action.MenuManager$2.menuShown(MenuManager.java:497) at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:256) at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:86) at org.eclipse.swt.widgets.Display.sendEvent(Display.java:5686) at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1370) at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1396) at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1375) at org.eclipse.swt.widgets.Menu.gtk_show(Menu.java:779) at org.eclipse.swt.widgets.Widget.windowProc(Widget.java:1935) at org.eclipse.swt.widgets.Display.windowProc(Display.java:5898) at org.eclipse.swt.internal.gtk.GTK._gtk_main_do_event(Native Method) at org.eclipse.swt.internal.gtk.GTK.gtk_main_do_event(GTK.java:4084) at org.eclipse.swt.widgets.Display.eventProc(Display.java:1383) at org.eclipse.swt.internal.gtk.OS._g_main_context_iteration(Native Method) at org.eclipse.swt.internal.gtk.OS.g_main_context_iteration(OS.java:1626) I haven't yet investigated why the language server is not responding in 10 seconds in this case, but I think it shouldn't matter, even if it's a server-side bug: the UI thread should never be blocked on an asynchronous operation such as communication with another process.
I seem to have similar problems on my Eclipse Photon installation at work. However, the stack trace is slightly different. I get UI lockups for several seconds at a time. This is very annoying. In my case, the lockups seem to happen when opening Maven pom.xml files from multi-module projects. I also think that these operations shouldn't block the UI thread. I tried cancelling the language server initialization manually and it didn't seem to effect the operations that I wanted to use.
Eclipse LSP4E is moving away from this bugs.eclipse.org issue tracker to https://github.com/eclipse/lsp4e/issues/ instead. If this issue is relevant to you, your action is required. 0. Verify this issue is still happening with latest LSP4E snapshots (from https://download.eclipse.org/lsp4e/snapshots ) if issue has disappeared, please change status of this issue to "CLOSED WORKFORME" with some details about your testing environment and how you did verify the issue; and you're done if issue is still present with snapshots: * Create a new issue at https://github.com/eclipse/lsp4e/issues/ ** Use as title in GitHub the title of this Bugzilla ticket (may include the bug number or not, at your own convenience) ** In the GitHub description, start with a link to this bugzilla ticket ** Optionally add new content to the description if it can helps towards resolution ** Submit GitHub issue * Update bugzilla ticket ** Add to "See also" property (up right column) the link to the newly created GitHub issue ** Add a comment "Migrated to <link-to-newly-created-GitHub-issue>" ** Set status as CLOSED MOVED ** Submit All issues that remain open will be automatically closed soon. Then the Bugzilla component for LSP4E will be archived and made read-only.
