--- /dev/null
+/*
+ * SPDX-License-Identifier: LGPL-2.1-only
+ *
+ * Copyright (C) 2015 EfficiOS Inc.
+ * Copyright (C) 2015 Alexandre Montplaisir <alexmonthy@efficios.com>
+ */
+
+package org.lttng.ust.agent.context;
+
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * The singleton manager of {@link IContextInfoRetriever} objects.
+ *
+ * @author Alexandre Montplaisir
+ */
+public final class ContextInfoManager {
+
+ private static final String SHARED_LIBRARY_NAME = "lttng-ust-context-jni";
+
+ private static final Pattern VALID_CONTEXT_NAME_PATTERN = Pattern.compile("^[a-zA-Z0-9_\\.]+$");
+
+ private static ContextInfoManager instance;
+
+ private final Map<String, IContextInfoRetriever> contextInfoRetrievers = new ConcurrentHashMap<String, IContextInfoRetriever>();
+ private final Map<String, Long> contextInforRetrieverRefs = new HashMap<String, Long>();
+
+ /**
+ * Lock used to keep the two maps above in sync when retrievers are
+ * registered or unregistered.
+ */
+ private final Object retrieverLock = new Object();
+
+ /** Singleton class, constructor should not be accessed directly */
+ private ContextInfoManager() {
+ }
+
+ /**
+ * Get the singleton instance.
+ *
+ * <p>
+ * Usage of this class requires the "liblttng-ust-context-jni.so" native
+ * library to be present on the system and available (passing
+ * -Djava.library.path=path to the JVM may be needed).
+ * </p>
+ *
+ * @return The singleton instance
+ * @throws IOException
+ * If the shared library cannot be found.
+ * @throws SecurityException
+ * We will forward any SecurityExcepion that may be thrown when
+ * trying to load the JNI library.
+ */
+ public static synchronized ContextInfoManager getInstance() throws IOException, SecurityException {
+ if (instance == null) {
+ try {
+ System.loadLibrary(SHARED_LIBRARY_NAME);
+ } catch (UnsatisfiedLinkError e) {
+ throw new IOException(e);
+ }
+ instance = new ContextInfoManager();
+ }
+ return instance;
+ }
+
+ /**
+ * Register a new context info retriever.
+ *
+ * <p>
+ * Each context info retriever is registered with a given "retriever name",
+ * which specifies the namespace of the context elements. This name is
+ * specified separately from the retriever objects, which would allow
+ * register the same retriever under different namespaces for example.
+ * </p>
+ *
+ * <p>
+ * If the method returns false (indicating registration failure), then the
+ * retriever object will *not* be used for context information.
+ * </p>
+ *
+ * @param retrieverName
+ * The name to register to the context retriever object with.
+ * @param contextInfoRetriever
+ * The context info retriever to register
+ * @return True if the retriever was successfully registered, false if there
+ * was an error, for example if a retriever is already registered
+ * with that name.
+ */
+ public boolean registerContextInfoRetriever(String retrieverName, IContextInfoRetriever contextInfoRetriever) {
+ synchronized (retrieverLock) {
+ if (!validateRetrieverName(retrieverName)) {
+ return false;
+ }
+
+ if (contextInfoRetrievers.containsKey(retrieverName)) {
+ /*
+ * There is already a retriever registered with that name,
+ * refuse the new registration.
+ */
+ return false;
+ }
+ /*
+ * Inform LTTng-UST of the new retriever. The names have to start
+ * with "$app." on the UST side!
+ */
+ long ref = LttngContextApi.registerProvider("$app." + retrieverName);
+ if (ref == 0) {
+ return false;
+ }
+
+ contextInfoRetrievers.put(retrieverName, contextInfoRetriever);
+ contextInforRetrieverRefs.put(retrieverName, Long.valueOf(ref));
+
+ return true;
+ }
+ }
+
+ /**
+ * Unregister a previously added context info retriever.
+ *
+ * This method has no effect if the retriever was not already registered.
+ *
+ * @param retrieverName
+ * The context info retriever to unregister
+ * @return True if unregistration was successful, false if there was an
+ * error
+ */
+ public boolean unregisterContextInfoRetriever(String retrieverName) {
+ synchronized (retrieverLock) {
+ if (!contextInfoRetrievers.containsKey(retrieverName)) {
+ /*
+ * There was no retriever registered with that name.
+ */
+ return false;
+ }
+ contextInfoRetrievers.remove(retrieverName);
+ long ref = contextInforRetrieverRefs.remove(retrieverName).longValue();
+
+ /* Unregister the retriever on the UST side too */
+ LttngContextApi.unregisterProvider(ref);
+
+ return true;
+ }
+ }
+
+ /**
+ * Return the context info retriever object registered with the given name.
+ *
+ * @param retrieverName
+ * The retriever name to look for
+ * @return The corresponding retriever object, or <code>null</code> if there
+ * was none
+ */
+ public IContextInfoRetriever getContextInfoRetriever(String retrieverName) {
+ /*
+ * Note that this method does not take the retrieverLock, it lets
+ * concurrent threads access the ConcurrentHashMap directly.
+ *
+ * It's fine for a get() to happen during a registration or
+ * unregistration, it's first-come-first-serve.
+ */
+ return contextInfoRetrievers.get(retrieverName);
+ }
+
+ /**
+ * Validate that the given retriever name contains only the allowed
+ * characters, which are alphanumerical characters, period "." and
+ * underscore "_". The name must also not start with a number.
+ */
+ private static boolean validateRetrieverName(String contextName) {
+ if (contextName.isEmpty()) {
+ return false;
+ }
+
+ /* First character must not be a number */
+ if (Character.isDigit(contextName.charAt(0))) {
+ return false;
+ }
+
+ /* Validate the other characters of the string */
+ Matcher matcher = VALID_CONTEXT_NAME_PATTERN.matcher(contextName);
+ return matcher.matches();
+ }
+}
projects / lttng-ust.git / blobdiff