Ticket

Class Overview

A ticket to access a named resource. When the resource is no longer needed, the ticket holder should close their ticket, allowing another request to acquire it. The preferred approach for this is to use a try-with-resources block:

     try (Ticket ticket = throttleService.acquireTicket("scm-command")) {
         //Do work, knowing the ticket will always be closed
     }

Note: The maximum duration for a ticket is scoped to the surrounding operation (where "operation" may be an HTTP request, an executed task or some other arbitrary unit of work). The system forcibly releases any tickets which are still held at the end of that bounding operation, where possible. This is done to help prevent resource starvation due to "lost" tickets, which are never otherwise released by their holding code.

Warning: Tickets are not thread-safe, and should never be passed across threads. Acquiring a ticket on one thread and releasing it on another thread will fail.

If a thread submits a Runnable on the ExecutorService exposed by the system or on any of the delegating ExecutorServices created by SAL's ThreadLocalDelegateExecutorFactory while holding a ticket, then the executor thread will implicitly inherit an internal "stub" of the calling thread's ticket. This "stub" ticket will act like a real ticket for the purposes of subsequent calls to the ThrottleService (preventing multiple tickets from being acquired in nested calls to acquireTicket(String) for example), but will not actually count towards the named resource and will not affect the calling thread's ticket in any way when released. A thread created in any other way (for example, with java.util.concurrent.ThreadFactory or by submitting a Runnable to a java.util.concurrent.Executor) does not inherit any ticket state from the calling thread, and must acquire its own ticket independently by calling acquireTicket(String)) if it wants to throttle access to the same resource. Any such tickets acquired in this way must be released with close() after the resource-intensive work has been done, to ensure no tickets are ever "lost".

Summary

[Expand] Inherited Methods
From interface java.lang.AutoCloseable void close()