package org.lttng.ust.agent.context;
-import java.util.Set;
-import java.util.concurrent.CopyOnWriteArraySet;
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
/**
* The singleton manager of {@link IContextInfoRetriever} objects.
*/
public final class ContextInfoManager {
- private static final ContextInfoManager INSTANCE = new ContextInfoManager();
+ private static final String SHARED_LIBRARY_NAME = "lttng-ust-context-jni";
- private final Set<IContextInfoRetriever> cirs = new CopyOnWriteArraySet<IContextInfoRetriever>();
+ private static ContextInfoManager instance;
+
+ private final Map<String, IContextInfoRetriever> contextInfoRetrievers = new ConcurrentHashMap<String, IContextInfoRetriever>();
+ private final Map<String, Long> contextInforRetrieverRefs = new HashMap<String, Long>();
+
+ 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
- * @deprecated The context-retrieving facilities are not yet implemented.
+ * @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.
*/
- @Deprecated
- public static ContextInfoManager getInstance() {
- return INSTANCE;
+ 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.
*
- * This method has no effect if the exact same retriever is already
- * registered.
+ * <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 cir
+ * @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 void addContextInfoRetriever(IContextInfoRetriever cir) {
- cirs.add(cir);
+ public boolean registerContextInfoRetriever(String retrieverName, IContextInfoRetriever contextInfoRetriever) {
+ synchronized (retrieverLock) {
+ 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;
+ }
}
/**
*
* This method has no effect if the retriever was not already registered.
*
- * @param cir
+ * @param retrieverName
* The context info retriever to unregister
+ * @return True if unregistration was successful, false if there was an
+ * error
*/
- public void removeContextInfoRetriever(IContextInfoRetriever cir) {
- cirs.remove(cir);
+ 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 a read-only view (does not support
- * {@link java.util.Iterator#remove}) of the currently registered context
- * info retrievers.
+ * Return the context info retriever object registered with the given name.
*
- * @return The current context info retrievers
+ * @param retrieverName
+ * The retriever name to look for
+ * @return The corresponding retriever object, or <code>null</code> if there
+ * was none
*/
- public Iterable<IContextInfoRetriever> getContextInfoRetrievers() {
- return cirs;
+ public IContextInfoRetriever getContextInfoRetriever(String retrieverName) {
+ return contextInfoRetrievers.get(retrieverName);
}
}
projects / deliverable / lttng-ust.git / blobdiff