InterProcessMutex is not releasing when called inside a future's onSuccess function.

[ibanner56]

We're trying to set up a lock for our Zookeeper operations, but when we attempt to call the release function, the entire application simply hangs on the call to release (that is, it prints the 'releasing lock' line, but not the 'lock released' line).

  get(byName) { request =>
    val topologyPromise = new Promise[ResponseBuilder]
    val topologyName = request.routeParams("name")
    val client = zkService.getCuratorClient
    val lock = new InterProcessMutex(client, s"${Config.ZOOKEEPER_APP_PATH}/locks/${topologyName.split("-")(0)}")
    if(lock.acquire(5, TimeUnit.SECONDS)){
      topologyService.getTopologyInfo(topologyName).onSuccess({ topology =>
        log.info("releasing lock")
        lock.release()
        log.info("lock released")
        topologyPromise.setValue(render.json(AppResponse(data = topology)))
      }).onFailure({ t: Throwable =>
        log.info(t.getMessage)
        lock.release()
        client.close()
        topologyPromise.setException(t)
      })
      }
    }
    else {
      log.info("No lock")
      topologyPromise.setValue(render.status(409).json(AppResponse(409, "Unable to acquire lock")))
    }

    topologyPromise
  }

If we use an await on the future, the release does not hang and releases correctly.

      try {
        val topology = Await.result(topologyService.getTopologyInfo(topologyName), Duration.fromMilliseconds(1000))
        topologyPromise.setValue(render.json(AppResponse(data = topology)))
      } catch { case ex: Exception =>
        topologyPromise.setException(ex)
      } finally {
        log.info("releasing lock")
        lock.release()
        log.info("lock released")
      }

[ibanner56]

I should mention that the onSuccess function _is_ running in the same thread as the acquire command - we initially tried to release the lock inside of a flatMap and received the error for trying to release from a thread that didn't own the lock.