How to wait until Spark service is stopped?

问题

For my Spark API I'm building integration tests. Sometimes I want to stop and start the Spark instance. When I do that I sometimes run into the problem that I'm creating a new Spark instance, while the old one is still shutting down on a separate thread. It would be helpful to know when the Spark instance actually shut down.

First I start my Spark instance like this:

Spark.init();
Spark.awaitInitialization();

Then I stop it like this:

Spark.stop();

Now after I call stop(), the Spark Service hasn't actually stopped!

Is there a similar functionality to awaitInitialization() or another way of knowing when the Spark service actually stopped?

回答1:

Spark 2.8.0 introduced an awaitStop() method: https://github.com/perwendel/spark/pull/730

If you are stuck at a version below (e.g. using spark-kotlin which uses Spark 2.6.0), you could use some reflection to identify the current state of Spark:

    fun awaitShutdown() {
        Spark.stop()

        while (isSparkInitialized()) {
            Thread.sleep(100)
        }
    }

    /**
     * Access the internals of Spark to check if the "initialized" flag is already set to false.
     */
    private fun isSparkInitialized(): Boolean {
        val sparkClass = Spark::class.java
        val getInstanceMethod = sparkClass.getDeclaredMethod("getInstance")
        getInstanceMethod.isAccessible = true
        val service = getInstanceMethod.invoke(null) as Service

        val serviceClass = service::class.java
        val initializedField = serviceClass.getDeclaredField("initialized")
        initializedField.isAccessible = true
        val initialized = initializedField.getBoolean(service)

        return initialized
    }

(extracted from https://github.com/debuglevel/sparkmicroserviceutils/blob/ec6b9692d808ecc448f1828f5487739101a2f62e/src/main/kotlin/de/debuglevel/microservices/utils/spark/SparkTestUtils.kt)

回答2:

I read this solution in https://github.com/perwendel/spark/issues/731 and works for me:

public static void stopServer() {
        try {
            Spark.stop();
            while (true) {
                try {
                    Spark.port();
                    Thread.sleep(500);
                } catch (final IllegalStateException ignored) {
                    break;
                }
            }
        } catch (final Exception ex) {
            // Ignore
        }
    }

回答3:

I use spark-java to build mock services for integration/ functional test.

My test tear down code:

public FakeServer shutdown() {
    service.stop();
    // Remove when https://github.com/perwendel/spark/issues/705 is fixed.
    try {
        Thread.sleep(100);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    return this;
}

Works seamlessly for me, each test sets up the FakeServer @Before and tears it down on test completion - @After.

Give it a shot.

来源：https://stackoverflow.com/questions/46451309/how-to-wait-until-spark-service-is-stopped

标签

java

spark-java