Handle OOM in Java language server

Add parameters to the java server to make lemminx crash
when it runs out of memory.
Detect when the java server shuts down due to running out of memory,
display a message to the user that this happened,
and don't attempt to restart the server.

Closes #527

Signed-off-by: David Thompson <davthomp@redhat.com>

Author: datho7561

docs/Troubleshooting.md

@@ -21,3 +21,23 @@ You can kill the process by:
 
   * on Windows OS: run `taskkill /F /PID ...` all instances
   * on other OS: run `kill -9 ...` all instances
+
+### The Language Server Crashes Due to an Out Of Memory Error
+
+If you are working with large XML files or referencing large schema files,
+it's likely that increasing the memory available to the language server will resolve this issue.
+
+If you aren't working with large XML files, then it may be a memory leak.
+Please [file a issue](https://github.com/redhat-developer/vscode-xml/issues) with a description of what you were doing if this is the case.
+
+#### How to increase the amount of memory available to the Language Server
+
+If you are using the Java Language Server:
+1. Go to settings
+2. Navigate to the setting `xml.server.vmargs`
+3. Add `-Xmx 1G` to the setting string. This allows the the language server to use at most 1 gigabyte of memory.
+4. If the problem persists, you can increase the `1G` to `2G` or higher
+
+If you are using the binary language server:
+1. By default, the language server will use up to 80% of your RAM.
+   Increasing this amount likely won't help solve the problem.

package-lock.json

@@ -68,6 +68,7 @@
   ],
   "devDependencies": {
     "@types/fs-extra": "^8.0.0",
+    "@types/glob": "^7.1.4",
     "@types/node": "^10.14.16",
     "@types/vscode": "^1.37.0",
     "@types/yauzl": "^2.9.1",

package.json

@@ -1,9 +1,14 @@
-import { window } from "vscode";
+import * as fs from "fs-extra";
+import * as path from "path";
+import { commands, window } from "vscode";
 import { CloseAction, ErrorAction, ErrorHandler, Message } from "vscode-languageclient";
+import { ClientCommandConstants } from "../commands/commandConstants";
+import glob = require("glob");
 
 /**
  * An error handler that restarts the language server,
- * unless it has been restarted 5 times in the last 3 minutes
+ * unless it has been restarted 5 times in the last 3 minutes,
+ * or if it crashed due to an Out Of Memory Error
  *
  * Adapted from [vscode-java](https://github.com/redhat-developer/vscode-java)
  */
@@ -23,6 +28,11 @@ export class ClientErrorHandler implements ErrorHandler {
 
   closed(): CloseAction {
     this.restarts.push(Date.now());
+    const heapProfileGlob = new glob.GlobSync(`${path.resolve(__dirname, '..')}/java_*.hprof`);
+    if (heapProfileGlob.found.length) {
+      showOOMMessage();
+      return CloseAction.DoNotRestart;
+    }
     if (this.restarts.length < 5) {
       return CloseAction.Restart;
     } else {
@@ -37,3 +47,32 @@ export class ClientErrorHandler implements ErrorHandler {
   }
 
 }
+
+/**
+ * Deletes all the heap dumps generated by Out Of Memory errors
+ *
+ * @returns when the heap dumps have been deleted
+ */
+export async function cleanUpHeapDumps(): Promise<void> {
+  const heapProfileGlob = new glob.GlobSync(`${path.resolve(__dirname, '..')}/java_*.hprof`);
+  for (let heapProfile of heapProfileGlob.found) {
+    await fs.remove(heapProfile);
+  }
+}
+
+/**
+ * Shows a message about the server crashing due to an out of memory issue
+ */
+async function showOOMMessage(): Promise<void> {
+  const DOCS = 'More info...';
+  const result = await window.showErrorMessage('The XML Language Server crashed due to an Out Of Memory Error, and will not be restarted. ', //
+    DOCS);
+  if (result === DOCS) {
+    await commands.executeCommand(ClientCommandConstants.OPEN_DOCS,
+      {
+        page: 'Troubleshooting',
+        section: 'the-language-server-crashes-due-to-an-out-of-memory-error'
+      }
+    );
+  }
+}

src/client/clientErrorHandler.ts

@@ -16,15 +16,16 @@ import { ExtensionContext, extensions, languages } from "vscode";
 import { Executable, LanguageClient } from 'vscode-languageclient/node';
 import { XMLExtensionApi } from './api/xmlExtensionApi';
 import { getXmlExtensionApiImplementation } from './api/xmlExtensionApiImplementation';
+import { cleanUpHeapDumps } from './client/clientErrorHandler';
 import { getIndentationRules } from './client/indentation';
 import { startLanguageClient } from './client/xmlClient';
+import { registerClientOnlyCommands } from './commands/registerCommands';
 import { collectXmlJavaExtensions } from './plugin';
 import * as requirements from './server/requirements';
 import { prepareExecutable } from './server/serverStarter';
 import { ExternalXmlSettings } from "./settings/externalXmlSettings";
 import { getXMLConfiguration } from './settings/settings';
 import { Telemetry } from './telemetry';
-import { registerClientOnlyCommands } from './commands/registerCommands';
 
 let languageClient: LanguageClient;
 
@@ -52,6 +53,7 @@ export async function activate(context: ExtensionContext): Promise<XMLExtensionA
     storagePath = os.homedir() + "/.lemminx";
   }
   const logfile = path.resolve(storagePath + '/lemminx.log');
+  await cleanUpHeapDumps();
 
   const externalXmlSettings: ExternalXmlSettings = new ExternalXmlSettings();
 

src/extension.ts

@@ -13,7 +13,7 @@ import { getProxySettings, getProxySettingsAsEnvironmentVariables, ProxySettings
 import { getXMLConfiguration } from "../../settings/settings";
 import { Telemetry } from '../../telemetry';
 import { addTrustedHash, getTrustedHashes } from './binaryHashManager';
-const glob = require('glob');
+import glob = require('glob');
 
 const HTTPS_PATTERN = /^https:\/\//;
 const JAR_ZIP_AND_HASH_REJECTOR = /(?:\.jar)|(?:\.zip)|(?:\.sha256)$/;
@@ -430,4 +430,4 @@ async function acceptBinaryDownloadResponse(response: http.IncomingMessage): Pro
 
 async function openProxyDocumentation(): Promise<void> {
   await commands.executeCommand(ClientCommandConstants.OPEN_DOCS, { page: "Proxy" });
-}
+}

src/server/binary/binaryServerStarter.ts

@@ -1,16 +1,31 @@
 import * as os from 'os';
 import * as path from 'path';
-import { ExtensionContext, workspace } from 'vscode';
+import { ExtensionContext, window, workspace } from 'vscode';
 import { Executable } from 'vscode-languageclient/node';
 import { getProxySettings, getProxySettingsAsJVMArgs, jvmArgsContainsProxySettings, ProxySettings } from '../../settings/proxySettings';
 import { getJavaagentFlag, getKey, getXMLConfiguration, IS_WORKSPACE_VMARGS_XML_ALLOWED, xmlServerVmargs } from '../../settings/settings';
 import { RequirementsData } from '../requirements';
-const glob = require('glob');
+import glob = require('glob');
 
 declare var v8debug;
 
 const DEBUG = (typeof v8debug === 'object') || startedInDebugMode();
 
+/**
+ * Argument that tells the program to crash when an OutOfMemoryError is raised
+ */
+const CRASH_ON_OOM = '-XX:+ExitOnOutOfMemoryError';
+
+/**
+ * Argument that tells the program to generate a heap dump file when an OutOfMemoryError is raised
+ */
+const HEAP_DUMP = '-XX:+HeapDumpOnOutOfMemoryError';
+
+/**
+ * Argument that tells the program where to generate the heap dump that is created when an OutOfMemoryError is raised and `HEAP_DUMP` has been passed
+ */
+const HEAP_DUMP_LOCATION = '-XX:HeapDumpPath=';
+
 export async function prepareJavaExecutable(
   context: ExtensionContext,
   requirements: RequirementsData,
@@ -63,6 +78,18 @@ function prepareParams(requirements: RequirementsData, xmlJavaExtensions: string
       params.push(watchParentProcess + 'false');
     }
   }
+  if (vmargs.indexOf(CRASH_ON_OOM) < 0) {
+    params.push(CRASH_ON_OOM);
+  }
+  if (vmargs.indexOf(HEAP_DUMP) < 0) {
+    params.push(HEAP_DUMP);
+  }
+  if (vmargs.indexOf(HEAP_DUMP_LOCATION) < 0) {
+    params.push(`${HEAP_DUMP_LOCATION}${path.resolve(__dirname, '..')}`);
+  } else {
+    window.showWarningMessage('Heap dump location has been modified; if you are experiencing Out Of Memory crashes, vscode-xml won\'t be able to detect them');
+  }
+
   // "OpenJDK 64-Bit Server VM warning: Options -Xverify:none and -noverify
   // were deprecated in JDK 13 and will likely be removed in a future release."
   // so only add -noverify for older versions