Handling connectivity issues in web service outbound gateway (retry)

[ach]

Currently, we have a requirement to attempt a WS request, and in the case that the remote endpoint is down, queue the request for retry. This queue should also be backed by a database, so that if the application goes down, the requests will be retried once it is restarted.

I am hoping that I can achieve this purely with Spring Integration. My thought was that I could use a WS Outbound Gateway, with a message-store-backed queue channel set as the error channel. The error channel would be polled, and the message would be sent to a retry gateway (via Service Activator) which would also hook up to the WS Outbound Gateway, and basically form a processing loop.

The idea of the Service Activator and retry Gateway was taken from one of Oleg's SpringOne 2GX examples. The polling is happening properly, but I can't figure out how to "complete the loop" and actually get the retry to happen. Oddly, the poller seems to stop after the retry gateway is invoked.

Here is what I have currently:

        <!-- Will replace this with a JDBC store later -->
        <bean id="testMessageStore" class="org.springframework.integration.store.SimpleMessageStore" />

        <int:channel id="wsRequestChannel" />
        <int:channel id="wsReplyChannel" />
        <int:channel id="wsErrorChannel">
            <int:queue message-store="testMessageStore" />
        </int:channel>

        <int:channel id="testChannel" />
        <int:chain input-channel="wsErrorChannel" auto-startup="true">
            <int:poller fixed-rate="5000">
                <int:transactional transaction-manager="transactionManager" />
            </int:poller>
            <int:transformer expression="payload.getFailedMessage().getPayload() + ' '" />
            <!-- Everything seems to work fine up to here, but how do I get it to retry the WS? -->
            <int:service-activator ref="retryGateway" />
        </int:chain>

        <int:chain input-channel="wsRequestChannel" output-channel="wsReplyChannel">
            <int-ws:header-enricher>
                <int-ws:soap-action value="theTargetSoapAction" />
            </int-ws:header-enricher>
            <int-ws:outbound-gateway id="testWsGateway" uri="https://someSOAPService" interceptor="wsSecurityInterceptor" />
        </int:chain>

        <int:gateway id="mainGateway" default-request-channel="wsRequestChannel" default-reply-channel="wsReplyChannel" error-channel="wsErrorChannel" service-interface="com.mypackage.IntegrationTestService">
            <int:method name="sendMessage" />
        </int:gateway>
        <int:gateway id="retryGateway" default-request-channel="wsRequestChannel" default-reply-channel="wsReplyChannel" error-channel="wsErrorChannel" />

Can anyone help with this, or offer up suggestions for alternative approaches?
Thanks!

[Cleric]

Hello

If you're going to use persistent MessageStore for <queue>, you just need to configure <transactional> <poller> on <ws:outbound-gateway> and after Exception on service the transaction will be rollbacked and your failed Message won't be removed from MessageStore. And on the next poll the last one will be sended to service again. So, to make simple retry it's enough to configure message-flow like this:

 <int:channel id="wsRequestChannel">
   <int:queue message-store="messageStore" />
</int:channel>

<int:chain input-channel="wsRequestChannel" output-channel="wsReplyChannel">
   <int:poller fixed-rate="5000">
       <int:transactional/>
    </int:poller>
    <int-ws:header-enricher>
        <int-ws:soap-action value="theTargetSoapAction" />
    </int-ws:header-enricher>
    <int-ws:outbound-gateway id="testWsGateway" uri="https://someSOAPService" interceptor="wsSecurityInterceptor" />
</int:chain>

However be careful about <gateway> as message-flow entry point: Message Store. "Important" paragraph.

Take care,
Artem Bilan

[ach]

Thanks for the reply. The reason why my approach may seem a bit convoluted, is that I would like for the first attempt at the web service call to be synchronous -- only when it fails should it be retried asynchronously. In this scenario, the poller rate would be something much slower: 5 mins, for example.

[Cleric]

OK, let it be
But <gateway> is still bad idea for <queue> with persistent MessageStore.
Nevertheless, how do you plan to process WS-response in the asynchronous retry sub-flow?

By the way, what you're looking for looks like this: http://forum.springsource.org/showthread.php?111867

Give me, please, more time to figure out how it should be in your case...

[ach]

OK, let it be
But <gateway> is still bad idea for <queue> with persistent MessageStore.

The use of a Gateway was mainly just because it's an easy way to start the message flow for my small proof-of-concept. I don't necessarily have to use it.

Nevertheless, how do you plan to process WS-response in the asynchronous retry sub-flow?

Probably just via some service method (is this possible with a Service Activator?).

By the way, what you're looking for looks like this: http://forum.springsource.org/showthread.php?111867

Thanks, I will take a look at that.

[Cleric]

Hi, again

So, I've builded some approximate test for your use case:

<int-jdbc:message-store id="messageStore" data-source="dataSource"/>

	<channel id="input"/>

	<channel id="output">
		<queue/>
	</channel>

	<channel id="retryChannel">
		<!--<queue/>-->
		<queue message-store="messageStore"/>
	</channel>

	<gateway service-interface="org.springframework.integration.jdbc.RetryViaMessageStoreTests$TestGateway"
			 error-channel="retryChannel">
		<method name="send" request-channel="input"/>
		<method name="receive" reply-channel="output"/>
	</gateway>

	<service-activator input-channel="input" output-channel="output" ref="service" method="serviceIt"/>

	<beans:bean id="service" class="org.springframework.integration.jdbc.RetryViaMessageStoreTests$TestService"/>

	<chain input-channel="retryChannel">
		<poller fixed-rate="100">
			<transactional/>
		</poller>
		<transformer expression="payload.failedMessage.payload"/>
		<gateway request-channel="input"/>
	</chain>

@ContextConfiguration
@RunWith(SpringJUnit4ClassRunner.class)
public class RetryViaMessageStoreTests {

	@Autowired
	private TestGateway gateway;

	@Test
	public void testIt() throws InterruptedException {
		gateway.send("test");
		assertEquals("TEST", gateway.receive());
	}


	private static interface TestGateway {

		void send(String s);

		String receive();
	}

	private static class TestService {

		private AtomicInteger counter = new AtomicInteger();

		public String serviceIt(String s) {
			System.out.println(counter);
			if (10 == counter.getAndIncrement()) {
				return s.toUpperCase();
			}
			throw new RuntimeException("intentional");

		}

	}

}

Here you can replace my <service-activator> with your WS-flow. If you change the 'retryChannel' <queue> to SimpleMessageStore you're going to lose message after first retry effort and your upstream invocation will hang on 'gateway.receive()'.
My test is passed after 10 retries.
Nevertheless you should try to use real robust solution with Spring-retry as it will be done after solving the issue: https://jira.springsource.org/browse/INT-343

Good luck