* This class provides the methods necessary for creating, starting, stopping, * and destroying recordings. * * @since 9 */ public final class FlightRecorder { private static volatile FlightRecorder platformRecorder; private static volatile boolean initialized; private final PlatformRecorder internal; private FlightRecorder(PlatformRecorder internal) { this.internal = internal; } /** * Returns an immutable list of the available recordings. *
* A recording becomes available when it is created. It becomes unavailable when it
* is in the {@code CLOSED} state, typically after a call to
* {@link Recording#close()}.
*
* @return a list of recordings, not {@code null}
*/
public List
* A snapshot is a synthesized recording in a stopped state. If no data is
* available, a recording with size {@code 0} is returned.
*
* A snapshot provides stable access to data for later operations (for example,
* operations to change the interval or to reduce the data size).
*
* Example,
*
*
* If the event class is already registered, then the invocation of this method is
* ignored.
*
* @param eventClass the event class to register, not {@code null}
*
* @throws IllegalArgumentException if class is abstract or not a subclass
* of {@link Event}
* @throws SecurityException if a security manager exists and the caller
* does not have {@code FlightRecorderPermission("registerEvent")}
*/
public static void register(Class eventClass) {
Objects.requireNonNull(eventClass);
if (JVMSupport.isNotAvailable()) {
return;
}
Utils.ensureValidEventSubclass(eventClass);
MetadataRepository.getInstance().register(eventClass);
}
/**
* Unregisters an event class.
*
* If the event class is not registered, then the invocation of this method is
* ignored.
*
* @param eventClass the event class to unregistered, not {@code null}
* @throws IllegalArgumentException if a class is abstract or not a subclass
* of {@link Event}
*
* @throws SecurityException if a security manager exists and the caller
* does not have {@code FlightRecorderPermission("registerEvent")}
*/
public static void unregister(Class eventClass) {
Objects.requireNonNull(eventClass);
if (JVMSupport.isNotAvailable()) {
return;
}
Utils.ensureValidEventSubclass(eventClass);
MetadataRepository.getInstance().unregister(eventClass);
}
/**
* Returns the Flight Recorder for the platform.
*
* @return a Flight Recorder instance, not {@code null}
*
* @throws IllegalStateException if the platform Flight Recorder couldn't be
* created (for example, if the file repository can't be created or
* accessed)
*
* @throws SecurityException if a security manager exists and the caller does
* not have {@code FlightRecorderPermission("accessFlightRecorder")}
*/
public static FlightRecorder getFlightRecorder() throws IllegalStateException, SecurityException {
synchronized (PlatformRecorder.class) {
Utils.checkAccessFlightRecorder();
JVMSupport.ensureWithIllegalStateException();
if (platformRecorder == null) {
try {
platformRecorder = new FlightRecorder(new PlatformRecorder());
} catch (IllegalStateException ise) {
throw ise;
} catch (Exception e) {
throw new IllegalStateException("Can't create Flight Recorder. " + e.getMessage(), e);
}
// Must be in synchronized block to prevent instance leaking out
// before initialization is done
initialized = true;
Logger.log(JFR, INFO, "Flight Recorder initialized");
Logger.log(JFR, DEBUG, "maxchunksize: " + Options.getMaxChunkSize()+ " bytes");
Logger.log(JFR, DEBUG, "memorysize: " + Options.getMemorySize()+ " bytes");
Logger.log(JFR, DEBUG, "globalbuffersize: " + Options.getGlobalBufferSize()+ " bytes");
Logger.log(JFR, DEBUG, "globalbuffercount: " + Options.getGlobalBufferCount());
Logger.log(JFR, DEBUG, "dumppath: " + Options.getDumpPath());
Logger.log(JFR, DEBUG, "samplethreads: " + Options.getSampleThreads());
Logger.log(JFR, DEBUG, "stackdepth: " + Options.getStackDepth());
Logger.log(JFR, DEBUG, "threadbuffersize: " + Options.getThreadBufferSize());
Logger.log(JFR, LogLevel.INFO, "Created repository " + Repository.getRepository().getRepositoryPath().toString());
PlatformRecorder.notifyRecorderInitialized(platformRecorder);
}
}
return platformRecorder;
}
/**
* Adds a callback for a periodic event.
*
* The implementation of the hook should return as soon as possible, to
* avoid blocking other Flight Recorder operations. The hook should emit
* one or more events of the specified type. When a hook is added, the
* interval at which the call is invoked is configurable using the
* {@code "period"} setting.
*
* @param eventClass the class that the hook should run for, not {@code null}
* @param hook the hook, not {@code null}
* @throws IllegalArgumentException if a class is not a subclass of
* {@link Event}, is abstract, or the hook is already added
* @throws IllegalStateException if the event class has the
* {@code Registered(false)} annotation and is not registered manually
* @throws SecurityException if a security manager exists and the caller
* does not have {@code FlightRecorderPermission("registerEvent")}
*/
public static void addPeriodicEvent(Class eventClass, Runnable hook) throws SecurityException {
Objects.requireNonNull(eventClass);
Objects.requireNonNull(hook);
if (JVMSupport.isNotAvailable()) {
return;
}
Utils.ensureValidEventSubclass(eventClass);
Utils.checkRegisterPermission();
AccessControlContext acc = AccessController.getContext();
RequestEngine.addHook(acc, EventType.getEventType(eventClass).getPlatformEventType(), hook);
}
/**
* Removes a callback hook for a periodic event.
*
* @param hook the hook to remove, not {@code null}
* @return {@code true} if hook is removed, {@code false} otherwise
* @throws SecurityException if a security manager exists and the caller
* does not have {@code FlightRecorderPermission("registerEvent")}
*/
public static boolean removePeriodicEvent(Runnable hook) throws SecurityException {
Objects.requireNonNull(hook);
Utils.checkRegisterPermission();
if (JVMSupport.isNotAvailable()) {
return false;
}
return RequestEngine.removeHook(hook);
}
/**
* Returns an immutable list that contains all currently registered events.
*
* By default, events are registered when they are first used, typically
* when an event object is allocated. To ensure an event is visible early,
* registration can be triggered by invoking the
* {@link FlightRecorder#register(Class)} method.
*
* @return list of events, not {@code null}
*/
public List
* If Flight Recorder is already initialized when the listener is added, the the method
* {@link FlightRecorderListener#recorderInitialized(FlightRecorder)} method is
* invoked before returning from this method.
*
* @param changeListener the listener to add, not {@code null}
*
* @throws SecurityException if a security manager exists and the caller
* does not have
* {@code FlightRecorderPermission("accessFlightRecorder")}
*/
public static void addListener(FlightRecorderListener changeListener) {
Objects.requireNonNull(changeListener);
Utils.checkAccessFlightRecorder();
if (JVMSupport.isNotAvailable()) {
return;
}
PlatformRecorder.addListener(changeListener);
}
/**
* Removes a recorder listener.
*
* If the same listener is added multiple times, only one instance is
* removed.
*
* @param changeListener listener to remove, not {@code null}
*
* @throws SecurityException if a security manager exists and the caller
* does not have
* {@code FlightRecorderPermission("accessFlightRecorder")}
*
* @return {@code true}, if the listener could be removed, {@code false}
* otherwise
*/
public static boolean removeListener(FlightRecorderListener changeListener) {
Objects.requireNonNull(changeListener);
Utils.checkAccessFlightRecorder();
if (JVMSupport.isNotAvailable()) {
return false;
}
return PlatformRecorder.removeListener(changeListener);
}
/**
* Returns {@code true} if the Java Virtual Machine (JVM) has Flight Recorder capabilities.
*
* This method can quickly check whether Flight Recorder can be
* initialized, without actually doing the initialization work. The value may
* change during runtime and it is not safe to cache it.
*
* @return {@code true}, if Flight Recorder is available, {@code false}
* otherwise
*
* @see FlightRecorderListener for callback when Flight Recorder is
* initialized
*/
public static boolean isAvailable() {
if (JVMSupport.isNotAvailable()) {
return false;
}
return JVM.getJVM().isAvailable();
}
/**
* Returns {@code true} if Flight Recorder is initialized.
*
* @return {@code true}, if Flight Recorder is initialized,
* {@code false} otherwise
*
* @see FlightRecorderListener for callback when Flight Recorder is
* initialized
*/
public static boolean isInitialized() {
return initialized;
}
// package private
PlatformRecording newInternalRecording(Map
*
*
* The caller must close the recording when access to the data is no longer
* needed.
*
* @return a snapshot of all available recording data, not {@code null}
*/
public Recording takeSnapshot() {
return internal.newSnapshot();
}
/**
* Registers an event class.
*
* try (Recording snapshot = FlightRecorder.getFlightRecorder().takeSnapshot()) {
* if (snapshot.getSize() > 0) {
* snapshot.setMaxSize(100_000_000);
* snapshot.setMaxAge(Duration.ofMinutes(5));
* snapshot.dump(Paths.get("snapshot.jfr"));
* }
* }
*
*