moved process reaper to commons and re-used it for boot-java-ls

eclipse-language-servers/org.springframework.tooling.ls.eclipse.commons/src/org/springframework/tooling/ls/eclipse/commons/LanguageServerProcessReaper.java

@@ -0,0 +1,115 @@
+/*******************************************************************************
+ * Copyright (c) 2017 Pivotal, Inc.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Pivotal, Inc. - initial API and implementation
+ *******************************************************************************/
+package org.springframework.tooling.ls.eclipse.commons;
+
+import java.lang.reflect.Field;
+import java.util.Iterator;
+import java.util.LinkedList;
+
+import org.eclipse.core.runtime.Platform;
+import org.eclipse.lsp4e.server.ProcessStreamConnectionProvider;
+
+/**
+ * A 'last resort cleanup' utility for LSP server processes. This class, when instantiated
+ * registers a JVM shutdown hook. When the hook is executed it kills of all tracked processes
+ * with the most aggressive process termination method available through the JRE.
+ * <p>
+ * This is meant only as a kind of 'fail-safe' as it is expected that lps4e does proper
+ * house-keeping and cleans up these processes automatically and cleanly. So... unless
+ * something goes wrong inside lsp4e then the `destroyProcesses` method really should
+ * just be iterating an empty collection of processes. I.e. the typical debug output
+ * on shutdown should look something like this:
+ * 
+ * <pre>
+ *  LanguageServerProcessReaper: Destroying errant processes... 
+ *  LanguageServerProcessReaper: Number of alive processes = 0
+ *  LanguageServerProcessReaper: Destroying errant processes... DONE
+ * </pre> 
+ * 
+ * @author Kris De Volder
+ */
+public class LanguageServerProcessReaper extends Thread {
+	
+	private static final boolean DEBUG = (""+Platform.getLocation()).contains("kdvolder");
+
+	private static void debug(String string) {
+		if (DEBUG) {
+			System.out.println("LanguageServerProcessReaper: "+string);
+		}
+	}
+
+	public static Process getProcess(ProcessStreamConnectionProvider connectionProvider) {
+		try {
+			//The super class is doesn't provide a way to get at the process without using reflection...
+			// This method can be removed if / when the super-class provides a getProcess method we can call.
+			Field processField = ProcessStreamConnectionProvider.class.getDeclaredField("process");
+			processField.setAccessible(true);
+			Process process = (Process) processField.get(connectionProvider);
+			return process;
+		} catch (NoSuchFieldException | SecurityException | IllegalArgumentException | IllegalAccessException e) {
+			return null;
+		}
+	}
+
+	LinkedList<Process> processes = new LinkedList<>();
+	{
+		Runtime.getRuntime().addShutdownHook(this);
+	}
+	
+	public synchronized void addProcess(Process process) {
+		debug("added process: "+process);
+		if (process!=null) {
+			processes.add(process);
+		}
+		garbageCollect();
+	}
+
+	/**
+	 * If processes are managed reasonably by lsp4e then we don't expect the list of
+	 * actually 'alive' processes to keep on growing. This checks for and removes
+	 * processes that are already dead.
+	 */
+	protected void garbageCollect() {
+		Process process;
+		Iterator<Process> iter = processes.iterator();
+		while (iter.hasNext()) {
+			process = iter.next();
+			if (!process.isAlive()) {
+				iter.remove();
+			}
+		}
+		debug("Number of alive processes = "+processes.size());
+	}
+
+	public synchronized void removeProcess(Process process) {
+		debug("removeProcess "+process);
+		garbageCollect();
+	}
+
+	@Override
+	public void run() {
+		destroyProcesses();
+	}
+
+	private synchronized void destroyProcesses() {
+		debug("Destroying errant processes... ");
+		garbageCollect();
+		for (Process process : processes) {
+			try {
+				debug("Destroying process "+process);
+				process.destroyForcibly();
+			} catch (Throwable e) {
+			}
+		}
+		debug("Destroying errant processes... DONE");
+	}
+
+}