From 5976d36bd92628c4ed11a8597c857f42ac76aef8 Mon Sep 17 00:00:00 2001
From: Kris De Volder <kdevolder@pivotal.io>
Date: Tue, 27 Jun 2017 17:00:45 -0700
Subject: [PATCH] Implement a 'fallback' lsp process reaper to cleanup errant
 processes.

---
 .../CloudFoundryManifestLanguageServer.java   |  23 ++++
 .../ls/LanguageServerProcessReaper.java       | 100 ++++++++++++++++++
 2 files changed, 123 insertions(+)
 create mode 100644 eclipse-language-servers/org.springframework.tooling.cloudfoundry.manifest.ls/src/org/springframework/tooling/cloudfoundry/manifest/ls/LanguageServerProcessReaper.java

diff --git a/eclipse-language-servers/org.springframework.tooling.cloudfoundry.manifest.ls/src/org/springframework/tooling/cloudfoundry/manifest/ls/CloudFoundryManifestLanguageServer.java b/eclipse-language-servers/org.springframework.tooling.cloudfoundry.manifest.ls/src/org/springframework/tooling/cloudfoundry/manifest/ls/CloudFoundryManifestLanguageServer.java
index 7e776553c..7e7bf68d0 100644
--- a/eclipse-language-servers/org.springframework.tooling.cloudfoundry.manifest.ls/src/org/springframework/tooling/cloudfoundry/manifest/ls/CloudFoundryManifestLanguageServer.java
+++ b/eclipse-language-servers/org.springframework.tooling.cloudfoundry.manifest.ls/src/org/springframework/tooling/cloudfoundry/manifest/ls/CloudFoundryManifestLanguageServer.java
@@ -13,6 +13,7 @@ package org.springframework.tooling.cloudfoundry.manifest.ls;
 import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
+import java.lang.reflect.Field;
 import java.net.URI;
 import java.nio.file.Files;
 import java.nio.file.StandardCopyOption;
@@ -38,6 +39,8 @@ import org.osgi.framework.Bundle;
 @SuppressWarnings("restriction")
 public class CloudFoundryManifestLanguageServer extends ProcessStreamConnectionProvider {
 	
+	private static LanguageServerProcessReaper processReaper = new LanguageServerProcessReaper();
+	
 	private LanguageServer languageServer;
 	private URI rootPath;
 
@@ -85,6 +88,7 @@ public class CloudFoundryManifestLanguageServer extends ProcessStreamConnectionP
 	public void stop() {
 		removeLanguageServer(this);
 		super.stop();
+		processReaper.removeProcess(this.getProcess());
 	}
 	
 	@Override
@@ -108,6 +112,25 @@ public class CloudFoundryManifestLanguageServer extends ProcessStreamConnectionP
 		return null;
 	}
 	
+	@Override
+	public void start() throws IOException {
+		super.start();
+		processReaper.addProcess(getProcess());
+	}
+	
+	private Process getProcess() {
+		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(this);
+			return process;
+		} catch (NoSuchFieldException | SecurityException | IllegalArgumentException | IllegalAccessException e) {
+			return null;
+		}
+	}
+
 	protected String getLanguageServerJARLocation() {
 		String languageServer = "manifest-yaml-language-server-" + Constants.LANGUAGE_SERVER_VERSION;
 
diff --git a/eclipse-language-servers/org.springframework.tooling.cloudfoundry.manifest.ls/src/org/springframework/tooling/cloudfoundry/manifest/ls/LanguageServerProcessReaper.java b/eclipse-language-servers/org.springframework.tooling.cloudfoundry.manifest.ls/src/org/springframework/tooling/cloudfoundry/manifest/ls/LanguageServerProcessReaper.java
new file mode 100644
index 000000000..f50b3d46a
--- /dev/null
+++ b/eclipse-language-servers/org.springframework.tooling.cloudfoundry.manifest.ls/src/org/springframework/tooling/cloudfoundry/manifest/ls/LanguageServerProcessReaper.java
@@ -0,0 +1,100 @@
+/*******************************************************************************
+ * Copyright (c) 2017 Spring IDE Developers
+ * 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:
+ *     Spring IDE Developers - initial API and implementation
+ *******************************************************************************/
+package org.springframework.tooling.cloudfoundry.manifest.ls;
+
+import java.util.Iterator;
+import java.util.LinkedList;
+
+import org.eclipse.core.runtime.Platform;
+
+/**
+ * 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);
+		}
+	}
+
+	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");
+	}
+
+}