javamelody#692 warn in the reports if multiple instances use the same…

… storage directory

javamelody-core/src/main/java/net/bull/javamelody/FilterContext.java

@@ -35,6 +35,7 @@
 import javax.management.MBeanServer;
 import javax.management.ObjectName;
 
+import net.bull.javamelody.internal.common.I18N;
 import net.bull.javamelody.internal.common.LOG;
 import net.bull.javamelody.internal.common.Parameters;
 import net.bull.javamelody.internal.model.Collector;
@@ -252,6 +253,10 @@ private void initCollect() {
 			return;
 		}
 
+		if (collector.isStorageUsedByMultipleInstances()) {
+			LOG.info(I18N.getString("storage_used_by_multiple_instances"));
+		}
+
 		try {
 			JRobin.initBackendFactory(timer);
 		} catch (final IOException e) {

javamelody-core/src/main/java/net/bull/javamelody/internal/model/Collector.java

@@ -74,6 +74,7 @@ public class Collector { // NOPMD
 	private final boolean noDatabase = Parameters.isNoDatabase();
 	private List<MetricsPublisher> metricsPublishers;
 	private final WebappVersions webappVersions;
+	private final StorageLock storageLock;
 
 	/**
 	 * Constructeur.
@@ -130,6 +131,9 @@ public Collector(String application, List<Counter> counters,
 					+ Parameters.getStorageDirectory(application), e);
 		}
 
+		// puis pose le lock
+		this.storageLock = new StorageLock(application);
+
 		this.webappVersions = new WebappVersions(application);
 	}
 
@@ -985,11 +989,19 @@ void clearCounter(String counterName) {
 		}
 	}
 
+	public boolean isStorageUsedByMultipleInstances() {
+		return !storageLock.isAcquired();
+	}
+
 	public void stop() {
 		try {
-			// on persiste les compteurs pour les relire à l'initialisation et ne pas perdre les stats
-			for (final Counter counter : counters) {
-				counter.writeToFile();
+			try {
+				// on persiste les compteurs pour les relire à l'initialisation et ne pas perdre les stats
+				for (final Counter counter : counters) {
+					counter.writeToFile();
+				}
+			} finally {
+				storageLock.release();
 			}
 		} catch (final IOException e) {
 			// persistance échouée, tant pis

javamelody-core/src/main/java/net/bull/javamelody/internal/model/StorageLock.java

@@ -0,0 +1,84 @@
+/*
+ * Copyright 2008-2017 by Emeric Vernat
+ *
+ *     This file is part of Java Melody.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package net.bull.javamelody.internal.model;
+
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.io.RandomAccessFile;
+import java.nio.channels.FileChannel;
+import java.nio.channels.FileLock;
+import java.nio.channels.OverlappingFileLockException;
+
+import net.bull.javamelody.internal.common.Parameters;
+
+/**
+ * Lock sur le répertoire de stockage pour détecter si des instances distinctes écrivent dans le même répertoire.
+ * @author Emeric Vernat
+ */
+class StorageLock {
+	private static final String LOCK_FILENAME = "javamelody.lock";
+	private final RandomAccessFile input;
+	private final FileChannel fileChannel;
+	private FileLock fileLock;
+
+	StorageLock(String application) {
+		super();
+		final File storageDir = Parameters.getStorageDirectory(application);
+		final File lockFile = new File(storageDir, LOCK_FILENAME);
+		try {
+			this.input = new RandomAccessFile(lockFile, "rw");
+			this.fileChannel = input.getChannel();
+		} catch (final FileNotFoundException e) {
+			throw new IllegalArgumentException(e);
+		}
+		// initialize the lock
+		getFileLock();
+	}
+
+	void release() throws IOException {
+		try {
+			if (fileLock != null) {
+				fileLock.release();
+			}
+		} finally {
+			try {
+				fileChannel.close();
+			} finally {
+				input.close();
+			}
+		}
+	}
+
+	private FileLock getFileLock() {
+		if (fileLock == null) {
+			try {
+				fileLock = fileChannel.tryLock();
+			} catch (final IOException e) {
+				return null;
+			} catch (final OverlappingFileLockException e) {
+				return null;
+			}
+		}
+		return fileLock;
+	}
+
+	boolean isAcquired() {
+		return getFileLock() != null;
+	}
+}

javamelody-core/src/main/java/net/bull/javamelody/internal/web/html/HtmlCoreReport.java

@@ -499,6 +499,11 @@ private void writeGraphs() throws IOException {
 			writeln("</div>");
 			return;
 		}
+		if (collector.isStorageUsedByMultipleInstances()) {
+			writeln("<div align='center' class='severe'><br/><br/>");
+			writeln("#storage_used_by_multiple_instances#");
+			writeln("</div><br/>");
+		}
 
 		writeGraphs(collector.getDisplayedCounterJRobins());
 		final Collection<JRobin> otherJRobins = collector.getDisplayedOtherJRobins();

javamelody-core/src/main/java/net/bull/javamelody/internal/web/pdf/PdfCoreReport.java

@@ -208,6 +208,12 @@ private void writeGraphs(Collection<JRobin> jrobins, Map<String, byte[]> mySmall
 			addToDocument(jrobinParagraph);
 			return;
 		}
+		if (collector.isStorageUsedByMultipleInstances()) {
+			final String message = getString("storage_used_by_multiple_instances") + "\n\n";
+			final Paragraph jrobinParagraph = new Paragraph(message, PdfFonts.BOLD.getFont());
+			jrobinParagraph.setAlignment(Element.ALIGN_CENTER);
+			addToDocument(jrobinParagraph);
+		}
 		final Paragraph jrobinParagraph = new Paragraph("",
 				FontFactory.getFont(FontFactory.HELVETICA, 9f, Font.NORMAL));
 		jrobinParagraph.setAlignment(Element.ALIGN_CENTER);

javamelody-core/src/main/resources/net/bull/javamelody/resource/translations.properties

@@ -621,3 +621,6 @@ Tableau_de_bord=Dashboard
 
 collect_server_misusage=Do not use this monitoring page if you use the optional collector server: \
 either use the monitoring page from the webapp, without a collector server, or use the page from the collector server
+
+storage_used_by_multiple_instances=Do not use the same storage directory with multiple instances or it will cause data loss. \
+Configure the storage-directory parameter if needed.

javamelody-core/src/main/resources/net/bull/javamelody/resource/translations_de.properties

@@ -621,3 +621,6 @@ Tableau_de_bord=
 
 collect_server_misusage=Nutzen Sie nicht diese Monitoring Seite, wenn Sie den optionalen collector server benutzen: \
 Bitte nutzen Sie stattdessen entweder die Monitoring Seite der webapp ohne einen collector server oder benutzen Sie die eigene Monitoring Seite des collector servers.
+
+storage_used_by_multiple_instances=Do not use the same storage directory with multiple instances or it will cause data loss. \
+Configure the storage-directory parameter if needed.

javamelody-core/src/main/resources/net/bull/javamelody/resource/translations_fr.properties

@@ -620,3 +620,6 @@ Tableau_de_bord=Tableau de bord
 
 collect_server_misusage=N'utilisez pas cette page de monitoring si vous utilisez le serveur de collecte optionnel : \
 utilisez soit la page de monitoring de cette webapp, sans un serveur de collecte, ou utilisez la page du serveur de collecte
+
+storage_used_by_multiple_instances=N'utilisez pas le même répertoire de stockage pour plusieurs instances ou cela causera des pertes de données. \
+Configurez le paramètre storage-directory si besoin.

javamelody-core/src/main/resources/net/bull/javamelody/resource/translations_pt.properties

@@ -625,3 +625,6 @@ Tableau_de_bord=Painel principal
 
 collect_server_misusage=Não use esta página de monitoramento se você usar o servidor coletor opcional: \
 use a página de monitoramento do webapp, Sem um collector server, ou use a página do collector server
+
+storage_used_by_multiple_instances=Do not use the same storage directory with multiple instances or it will cause data loss. \
+Configure the storage-directory parameter if needed.

javamelody-core/src/main/resources/net/bull/javamelody/resource/translations_zh.properties

@@ -947,3 +947,6 @@ thread_interrupt_sent = Thread interrupt signal sent
 send_thread_interrupt=Send a thread interrupt signal to {0}. The thread can test Thread.currentThread().isInterrupted() to stop itself.
 confirm_send_thread_interrupt=Do you confirm the sending of a thread interrupt signal to {0}?
 Interrupt=Interrupt
+
+storage_used_by_multiple_instances=Do not use the same storage directory with multiple instances or it will cause data loss. \
+Configure the storage-directory parameter if needed.