Adds this ServerBinding to the actor system's coordinated shutdown, so that unbind and terminate get called appropriately before the system is shut down.

Triggers "graceful" termination request being handled on this connection.

Termination works as follows:

1) Unbind: - the server port is unbound; no new connections will be accepted.

1.5) Immediately the ServerBinding whenTerminationSignalIssued future is completed. This can be used to signal parts of the application that the http server is shutting down and they should clean up as well. Note also that for more advanced shut down scenarios you may want to use the Coordinated Shutdown capabilities of Akka.

2) if a connection has no "in-flight" request, it is terminated immediately

3) Handle in-flight request: - if a request is "in-flight" (being handled by user code), it is given hardDeadline time to complete,

• if user code emits a response within the timeout, then this response is sent to the client with a Connection: close header and the connection is closed.
  • however if it is a streaming response, it is also mandated that it shall complete within the deadline, and if it does not the connection will be terminated regardless of status of the streaming response (this is because such response could be infinite, which could trap the server in a situation where it could not terminate if it were to wait for a response to "finish")
  • existing streaming responses must complete before the deadline as well. When the deadline is reached the connection will be terminated regardless of status of the streaming responses.
• if user code does not reply with a response within the deadline we produce a special pekko.http.javadsl.settings.ServerSettings.getTerminationDeadlineExceededResponse HTTP response (e.g. 503 Service Unavailable)

4) Keep draining incoming requests on existing connection: - The existing connection will remain alive for until the hardDeadline is exceeded, yet no new requests will be delivered to the user handler. All such drained responses will be replied to with an termination response (as explained in phase 3).

5) Close still existing connections - Connections are terminated forcefully once the hardDeadline is exceeded. The whenTerminated future is completed as well, so the graceful termination (of the ActorSystem or entire JVM itself can be safely performed, as by then it is known that no connections remain alive to this server).

Note that the termination response is configurable in pekko.http.javadsl.settings.ServerSettings, and by default is an 503 Service Unavailable, with an empty response entity.

Asynchronously triggers the unbinding of the port that was bound by the materialization of the connections pekko.stream.javadsl.Source

The produced java.util.concurrent.CompletionStage is fulfilled when the unbinding has been completed.

This completion stage completes when the termination process, as initiated by an terminate call has completed. This means that the server is by then: unbound, and has closed all existing connections.

This signal can for example be used to safely terminate the underlying ActorSystem.

Note: This mechanism is currently NOT hooked into the Coordinated Shutdown mechanisms of Akka. TODO: This feature request is tracked by: https://github.com/apache/incubator-pekko-http/issues/1210

Note that this signal may be used for Coordinated Shutdown to proceed to next steps in the shutdown. You may also explicitly depend on this completion stage to perform your next shutting down steps.

Completes when the terminate is called and server termination is in progress. Can be useful to make parts of your application aware that termination has been issued, and they have java.time.Duration time remaining to clean-up before the server will forcefully close existing connections.

Note that while termination is in progress, no new connections will be accepted (i.e. termination implies prior unbind).