RemoteRecordingStream (Java SE 25 & JDK 25)
Description: declaration: module: jdk.management.jfr, package: jdk.management.jfr, class: RemoteRecordingStream
Keywords: jdk.management.jfr.RemoteRecordingStream class

# Class RemoteRecordingStream

java.lang.Object
jdk.management.jfr.RemoteRecordingStream

All Implemented Interfaces:
  `AutoCloseable, EventStream`

public final class RemoteRecordingStream extends Object implements EventStream
An implementation of an `EventStream` that can serialize events over the network using an `MBeanServerConnection`.

The following example shows how to record garbage collection pauses and CPU usage on a remote host and print the events to standard out.

        String host = "com.example";
        int port = 4711;

        String url = "service:jmx:rmi:///jndi/rmi://" + host + ":" + port + "/jmxrmi";

        JMXServiceURL u = new JMXServiceURL(url);
        JMXConnector c = JMXConnectorFactory.connect(u);
        MBeanServerConnection conn = c.getMBeanServerConnection();

        try (var rs = new RemoteRecordingStream(conn)) {
            rs.enable("jdk.GCPhasePause").withoutThreshold();
            rs.enable("jdk.CPULoad").withPeriod(Duration.ofSeconds(1));
            rs.onEvent("jdk.CPULoad", System.out::println);
            rs.onEvent("jdk.GCPhasePause", System.out::println);
            rs.start();
        }

Since:
  16

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `RemoteRecordingStream(MBeanServerConnection connection)`
  Creates an event stream that operates against a `MBeanServerConnection` that has a registered `FlightRecorderMXBean`.
  `RemoteRecordingStream(MBeanServerConnection connection, Path directory)`
  Creates an event stream that operates against a `MBeanServerConnection` that has a registered `FlightRecorderMXBean`.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `awaitTermination()`
  Blocks until all actions are completed, or the stream is closed, or the current thread is interrupted, whichever happens first.
  `void`
  `awaitTermination(Duration timeout)`
  Blocks until all actions are completed, or the stream is closed, or the timeout occurs, or the current thread is interrupted, whichever happens first.
  `void`
  `close()`
  Releases all resources associated with this stream.
  `EventSettings`
  `disable(String name)`
  Disables event with the specified name.
  `void`
  `dump(Path destination)`
  Writes recording data to a file.
  `EventSettings`
  `enable(String name)`
  Enables the event with the specified name.
  `void`
  `onClose(Runnable action)`
  Registers an action to perform when the stream is closed.
  `void`
  `onError(Consumer<Throwable> action)`
  Registers an action to perform if an exception occurs.
  `void`
  `onEvent(String eventName, Consumer<RecordedEvent> action)`
  Registers an action to perform on all events matching a name.
  `void`
  `onEvent(Consumer<RecordedEvent> action)`
  Registers an action to perform on all events in the stream.
  `void`
  `onFlush(Runnable action)`
  Registers an action to perform after the stream has been flushed.
  `boolean`
  `remove(Object action)`
  Unregisters an action.
  `void`
  `setEndTime(Instant endTime)`
  Specifies the end time of the stream.
  `void`
  `setMaxAge(Duration maxAge)`
  Determines how far back data is kept for the stream.
  `void`
  `setMaxSize(long maxSize)`
  Determines how much data is kept for the stream.
  `void`
  `setOrdered(boolean ordered)`
  Specifies that events arrives in chronological order, sorted by the time they were committed to the stream.
  `void`
  `setReuse(boolean reuse)`
  Specifies that the event object in an `EventStream.onEvent(Consumer)` action can be reused.
  `void`
  `setSettings(Map<String,String> settings)`
  Replaces all settings for this recording stream.
  `void`
  `setStartTime(Instant startTime)`
  Specifies the start time of the stream.
  `void`
  `start()`
  Starts processing of actions.
  `void`
  `startAsync()`
  Starts asynchronous processing of actions.
  `boolean`
  `stop()`
  Stops the recording stream.

  ### Methods declared in class Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

  ### Methods declared in interface EventStream

  `onMetadata`

- ## Constructor Details

  - ### RemoteRecordingStream

    public RemoteRecordingStream(MBeanServerConnection connection) throws IOException
    Creates an event stream that operates against a `MBeanServerConnection` that has a registered `FlightRecorderMXBean`.

    To configure event settings, use `setSettings(Map)`.

    Parameters:
      `connection` - the `MBeanServerConnection` where the `FlightRecorderMXBean` is registered, not `null`
    Throws:
      `IOException` - if a stream can't be opened, an I/O error occurs when trying to access the repository or the `FlightRecorderMXBean`

  - ### RemoteRecordingStream

    public RemoteRecordingStream(MBeanServerConnection connection, Path directory) throws IOException
    Creates an event stream that operates against a `MBeanServerConnection` that has a registered `FlightRecorderMXBean`.

    To configure event settings, use `setSettings(Map)`.

    Parameters:
      `connection` - the `MBeanServerConnection` where the `FlightRecorderMXBean` is registered, not `null`
      `directory` - the directory to store event data that is downloaded, not `null`
    Throws:
      `IOException` - if a stream can't be opened, an I/O error occurs when trying to access the repository or the `FlightRecorderMXBean`

- ## Method Details

  - ### setSettings

    public void setSettings(Map<String,String> settings)
    Replaces all settings for this recording stream.

    The following example connects to a remote host and stream events using settings from the "default" configuration.

        {

            String host = "com.example";
            int port = 4711;

            String url = "service:jmx:rmi:///jndi/rmi://" + host + ":" + port + "/jmxrmi";

            JMXServiceURL u = new JMXServiceURL(url);
            JMXConnector c = JMXConnectorFactory.connect(u);
            MBeanServerConnection conn = c.getMBeanServerConnection();

            try (final var rs = new RemoteRecordingStream(conn)) {
                rs.onMetadata(e -> {
                    for (Configuration c : e.getConfigurations()) {
                        if (c.getName().equals("default")) {
                            rs.setSettings(c.getSettings());
                        }
                    }
                });
                rs.onEvent(System.out::println);
                rs.start();
            }

    Parameters:
      `settings` - the settings to set, not `null`
    See Also:
      - `Recording.setSettings(Map)`

  - ### disable

    public EventSettings disable(String name)
    Disables event with the specified name.

    If multiple events with same name (for example, the same class is loaded in different class loaders), then all events that match the name are disabled.

    Parameters:
      `name` - the settings for the event, not `null`
    Returns:
      an event setting for further configuration, not `null`

  - ### enable

    public EventSettings enable(String name)
    Enables the event with the specified name.

    If multiple events have the same name (for example, the same class is loaded in different class loaders), then all events that match the name are enabled.

    Parameters:
      `name` - the settings for the event, not `null`
    Returns:
      an event setting for further configuration, not `null`
    See Also:
      - `EventType`

  - ### setMaxAge

    public void setMaxAge(Duration maxAge)
    Determines how far back data is kept for the stream.

    To control the amount of recording data stored on disk, the maximum length of time to retain the data can be specified. Data stored on disk that is older than the specified length of time is removed by the Java Virtual Machine (JVM).

    If neither maximum limit or the maximum age is set, the size of the recording may grow indefinitely if events are not consumed.

    Parameters:
      `maxAge` - the length of time that data is kept, or `null` if infinite
    Throws:
      `IllegalArgumentException` - if `maxAge` is negative
      `IllegalStateException` - if the recording is in the `CLOSED` state

  - ### setMaxSize

    public void setMaxSize(long maxSize)
    Determines how much data is kept for the stream.

    To control the amount of recording data that is stored on disk, the maximum amount of data to retain can be specified. When the maximum limit is exceeded, the Java Virtual Machine (JVM) removes the oldest chunk to make room for a more recent chunk.

    If neither maximum limit or the maximum age is set, the size of the recording may grow indefinitely if events are not consumed.

    The size is measured in bytes.

    Parameters:
      `maxSize` - the amount of data to retain, `0` if infinite
    Throws:
      `IllegalArgumentException` - if `maxSize` is negative
      `IllegalStateException` - if the recording is in `CLOSED` state

  - ### onEvent

    public void onEvent(Consumer<RecordedEvent> action)
    Description copied from interface: `EventStream`
    Registers an action to perform on all events in the stream.

    To perform an action on a subset of event types, consider using `EventStream.onEvent(String, Consumer)` and `EventStream.onMetadata(Consumer)` as it is likely more performant than any selection or filtering mechanism implemented in a generic action.

    Specified by:
      `onEvent` in interface `EventStream`
    Parameters:
      `action` - an action to perform on each `RecordedEvent`, not `null`
    See Also:
      - `EventStream.onEvent(Consumer)`
      - `EventStream.onMetadata(Consumer)`

  - ### onEvent

    public void onEvent(String eventName, Consumer<RecordedEvent> action)
    Description copied from interface: `EventStream`
    Registers an action to perform on all events matching a name.
    Specified by:
      `onEvent` in interface `EventStream`
    Parameters:
      `eventName` - the name of the event, not `null`
      `action` - an action to perform on each `RecordedEvent` matching the event name, not `null`

  - ### onFlush

    public void onFlush(Runnable action)
    Description copied from interface: `EventStream`
    Registers an action to perform after the stream has been flushed.
    Specified by:
      `onFlush` in interface `EventStream`
    Parameters:
      `action` - an action to perform after the stream has been flushed, not `null`

  - ### onError

    public void onError(Consumer<Throwable> action)
    Description copied from interface: `EventStream`
    Registers an action to perform if an exception occurs.

    If an action is not registered, an exception stack trace is printed to standard error.

    Registering an action overrides the default behavior. If multiple actions have been registered, they are performed in the order of registration.

    If this method itself throws an exception, resulting behavior is undefined.

    Specified by:
      `onError` in interface `EventStream`
    Parameters:
      `action` - an action to perform if an exception occurs, not `null`

  - ### onClose

    public void onClose(Runnable action)
    Description copied from interface: `EventStream`
    Registers an action to perform when the stream is closed.

    If the stream is already closed, the action will be performed immediately in the current thread.

    Specified by:
      `onClose` in interface `EventStream`
    Parameters:
      `action` - an action to perform after the stream is closed, not `null`
    See Also:
      - `EventStream.close()`

  - ### close

    public void close()
    Description copied from interface: `EventStream`
    Releases all resources associated with this stream.

    If a stream is started, asynchronously or synchronously, it is stopped immediately or after the next flush. This method does NOT guarantee that all registered actions are completed before return.

    Closing a previously closed stream has no effect.

    Specified by:
      `close` in interface `AutoCloseable`
    Specified by:
      `close` in interface `EventStream`

  - ### remove

    public boolean remove(Object action)
    Description copied from interface: `EventStream`
    Unregisters an action.

    If the action has been registered multiple times, all instances are unregistered.

    Specified by:
      `remove` in interface `EventStream`
    Parameters:
      `action` - the action to unregister, not `null`
    Returns:
      `true` if the action was unregistered, `false` otherwise
    See Also:
      - `EventStream.onEvent(Consumer)`
      - `EventStream.onEvent(String, Consumer)`
      - `EventStream.onFlush(Runnable)`
      - `EventStream.onClose(Runnable)`
      - `EventStream.onError(Consumer)`

  - ### setReuse

    public void setReuse(boolean reuse)
    Description copied from interface: `EventStream`
    Specifies that the event object in an `EventStream.onEvent(Consumer)` action can be reused.

    If reuse is set to `true`, an action should not keep a reference to the event object after the action has completed.

    Specified by:
      `setReuse` in interface `EventStream`
    Parameters:
      `reuse` - `true` if an event object can be reused, `false` otherwise

  - ### setOrdered

    public void setOrdered(boolean ordered)
    Description copied from interface: `EventStream`
    Specifies that events arrives in chronological order, sorted by the time they were committed to the stream.
    Specified by:
      `setOrdered` in interface `EventStream`
    Parameters:
      `ordered` - if event objects arrive in chronological order to `EventStream.onEvent(Consumer)`

  - ### setStartTime

    public void setStartTime(Instant startTime)
    Description copied from interface: `EventStream`
    Specifies the start time of the stream.

    The start time must be set before starting the stream

    Specified by:
      `setStartTime` in interface `EventStream`
    Parameters:
      `startTime` - the start time, not `null`
    See Also:
      - `EventStream.start()`
      - `EventStream.startAsync()`

  - ### setEndTime

    public void setEndTime(Instant endTime)
    Description copied from interface: `EventStream`
    Specifies the end time of the stream.

    The end time must be set before starting the stream.

    At end time, the stream is closed.

    Specified by:
      `setEndTime` in interface `EventStream`
    Parameters:
      `endTime` - the end time, not `null`
    See Also:
      - `EventStream.start()`
      - `EventStream.startAsync()`

  - ### start

    public void start()
    Description copied from interface: `EventStream`
    Starts processing of actions.

    Actions are performed in the current thread.

    To stop the stream, use the `EventStream.close()` method.

    Specified by:
      `start` in interface `EventStream`

  - ### startAsync

    public void startAsync()
    Description copied from interface: `EventStream`
    Starts asynchronous processing of actions.

    Actions are performed in a single separate thread.

    To stop the stream, use the `EventStream.close()` method.

    Specified by:
      `startAsync` in interface `EventStream`

  - ### stop

    public boolean stop()
    Stops the recording stream.

    Stops a started stream and waits until all events in the recording have been consumed.

    Invoking this method in an action, for example in the `onEvent(Consumer)` method, could block the stream indefinitely. To stop the stream abruptly, use the `close()` method.

    The following code snippet illustrates how this method can be used in conjunction with the `startAsync()` method to monitor what happens during a test method:

          AtomicLong bytesWritten = new AtomicLong();
          try (var r = new RemoteRecordingStream(connection)) {
            r.setMaxSize(Long.MAX_VALUE);
            r.enable("jdk.FileWrite").withoutThreshold();
            r.onEvent(event ->
              bytesWritten.addAndGet(event.getLong("bytesWritten"))
            );
            r.startAsync();
            testFoo();
            r.stop();
            if (bytesWritten.get() > 1_000_000L) {
              r.dump(Path.of("file-write-events.jfr"));
              throw new AssertionError("testFoo() writes too much data to disk");
            }
          }

    Returns:
      `true` if recording is stopped, `false` otherwise
    Throws:
      `IllegalStateException` - if the recording is not started or is already stopped
    Since:
      20

  - ### dump

    public void dump(Path destination) throws IOException
    Writes recording data to a file.

    The recording stream must be started, but not closed.

    It's highly recommended that a max age or max size is set before starting the stream. Otherwise, the dump may not contain any events.

    Parameters:
      `destination` - the location where recording data is written, not `null`
    Throws:
      `IOException` - if the recording data can't be copied to the specified location, or if the stream is closed, or not started.
    Since:
      17
    See Also:
      - `setMaxAge(Duration)`
      - `setMaxSize(long)`

  - ### awaitTermination

    public void awaitTermination(Duration timeout) throws InterruptedException
    Description copied from interface: `EventStream`
    Blocks until all actions are completed, or the stream is closed, or the timeout occurs, or the current thread is interrupted, whichever happens first.
    Specified by:
      `awaitTermination` in interface `EventStream`
    Parameters:
      `timeout` - the maximum time to wait, not `null`
    Throws:
      `InterruptedException` - if interrupted while waiting
    See Also:
      - `EventStream.start()`
      - `EventStream.startAsync()`
      - `Thread.interrupt()`

  - ### awaitTermination

    public void awaitTermination() throws InterruptedException
    Description copied from interface: `EventStream`
    Blocks until all actions are completed, or the stream is closed, or the current thread is interrupted, whichever happens first.
    Specified by:
      `awaitTermination` in interface `EventStream`
    Throws:
      `InterruptedException` - if interrupted while waiting
    See Also:
      - `EventStream.start()`
      - `EventStream.startAsync()`
      - `Thread.interrupt()`