Package com.vaadin.flow.server

Interface SessionLockListener

All Superinterfaces:
Serializable
@Deprecated(since="25.3", forRemoval=true) public interface SessionLockListener extends Serializable
Deprecated, for removal: This API element is subject to removal in a future version.
add listeners for SessionLockRequestedEvent, SessionLockAcquiredEvent and SessionLockReleasedEvent on the service event bus instead
Listener that is notified when a Vaadin session lock is acquired and released, enabling observation of session-lock contention (for example to publish lock wait and hold-time metrics).

All Vaadin server-side work for a single session is serialized behind one lock, so the time a thread blocks acquiring it and the time it holds it are key performance signals. Callbacks are delivered for the outermost acquisition only (reentrant re-locks are not reported), and the three callbacks for a single hold are delivered on the same thread in the order lockRequested(com.vaadin.flow.server.SessionLockEvent), lockAcquired(com.vaadin.flow.server.SessionLockEvent), lockReleased(com.vaadin.flow.server.SessionLockEvent), so a listener can record the start time in a ThreadLocal on lockRequested, derive the wait time on lockAcquired, and the hold time on lockReleased.

When several listeners are registered, lockRequested(com.vaadin.flow.server.SessionLockEvent) and lockAcquired(com.vaadin.flow.server.SessionLockEvent) are delivered in registration order while lockReleased(com.vaadin.flow.server.SessionLockEvent) is delivered in reverse registration order, so the callbacks nest like try/finally blocks: a listener registered later sees its lockReleased run before that of a listener registered earlier.

Implementations must be fast and non-blocking: callbacks run on the request/access thread directly around the lock operation. Exceptions thrown from a callback are logged and suppressed so they cannot disrupt session locking.

Register via VaadinService.addSessionLockListener(SessionLockListener), typically from a VaadinServiceInitListener. Listeners registered after a session's lock has already been created are still honoured.

Since:
25.2
See Also:

  • Method Summary

    Modifier and Type
    Method
    Description
    default void
    lockAcquired(SessionLockEvent event)
    Deprecated, for removal: This API element is subject to removal in a future version.
    Invoked on the locking thread immediately after it has acquired the session lock for an outermost acquisition.
    default void
    lockReleased(SessionLockEvent event)
    Deprecated, for removal: This API element is subject to removal in a future version.
    Invoked on the locking thread immediately after the outermost lock hold has been released (the lock's hold count reached zero).
    default void
    lockRequested(SessionLockEvent event)
    Deprecated, for removal: This API element is subject to removal in a future version.
    Invoked on the locking thread immediately before it attempts to acquire the session lock for an outermost (non-reentrant) acquisition.

  • Method Details

    • lockRequested

      default void lockRequested(SessionLockEvent event)
      Deprecated, for removal: This API element is subject to removal in a future version.
      Invoked on the locking thread immediately before it attempts to acquire the session lock for an outermost (non-reentrant) acquisition. The thread may block between this callback and lockAcquired(com.vaadin.flow.server.SessionLockEvent); the elapsed time is the lock wait time. For a non-blocking acquisition (tryLock) this is delivered together with lockAcquired(com.vaadin.flow.server.SessionLockEvent) only when the lock was actually taken, so the reported wait time is effectively zero.
      Parameters:
      event - the session lock event

    • lockAcquired

      default void lockAcquired(SessionLockEvent event)
      Deprecated, for removal: This API element is subject to removal in a future version.
      Invoked on the locking thread immediately after it has acquired the session lock for an outermost acquisition.
      Parameters:
      event - the session lock event

    • lockReleased

      default void lockReleased(SessionLockEvent event)
      Deprecated, for removal: This API element is subject to removal in a future version.
      Invoked on the locking thread immediately after the outermost lock hold has been released (the lock's hold count reached zero). The time since lockAcquired(com.vaadin.flow.server.SessionLockEvent) is the lock hold time.
      Parameters:
      event - the session lock event