Please clarify one thing for me. Because what I understand SCC operating model starts on producer side. So I can have situation where I am able to modify contract definition then build and deploy producer without any test failures and my consumer will not know about that change until they are build right? So In theory I can endup on production with failing contracts between my producer and consumer until I will rebuild consumer found out about change and fix it. Is that valid scenario ?
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I have a set of microservices using springboot rest. These microservices will be deployed in a autoscaled and load balanced environment. One of these services is responsible for managing the system's configuration. When other microservices startup, they obtain the configuration from this service. If and when the configuration is updated, I need to inform all currently running microservices instances to update their cached configuration.
I am considering using RabbitMQ with a fanout exchange. In this solution, each instance at startup will create its queue and bind that queue to the exchange. When there is a configuration change, the configuration service will publish an update to all queues currently bound to that exchange.
However, as service instances are deleted, I cannot figure out how would I delete the queue specific to that instance. I googled but could not find a complete working example of a solution.
Any help or advise?
The idea and solution is correct. What you just miss that those queues, created by your consumer services could be declared as auto-delete=true: https://www.rabbitmq.com/queues.html. As long as your service is UP, the queue is there as well. You stop your service, its consumers are stopped and unsubscribed. At the moment the last consumer is unsubscribed the queue is deleted from the broker.
On the other hand I would suggest to look into Spring Cloud Bus project which really is aimed for tasks like this: https://spring.io/projects/spring-cloud-bus.
We have a set of microservices communicating with each other and some external downstream services. Spring Cloud Contract is used for integration tests to check the service interfaces. I'm able to test the contracts for communication between the microservices.
I'd like to know how to write the contract tests for a producer which
doesn't provide any contracts (cannot access source code)
SOAP-based
Can I impose the contracts from the consumer itself?
Couldn't find the SCC documentation helpful in this regard. Any helpful pointers are appreciated. Thanks!
If it's SOAP based then it's a standard XML based communication. You can generate XML based contracts (an example is here https://docs.spring.io/spring-cloud-contract/docs/current-SNAPSHOT/reference/htmlsingle/#contract-dsl-xml ). Now as for the one where you don't have access to source code, what you can is the following:
You can create a test that will go via a proxy (e.g. WireMock proxy) to the real application and that way you will store that communication in a form of stubs (https://www.youtube.com/watch?v=ZyHG-VOzPZg), you can also check the code (https://github.com/spring-cloud-samples/the-legacy-app/tree/master/stubs_with_proxy). The problem here is that the producer might not be idempotent or may require a lot of concrete setup on the input to get proper response (e.g. a precisely defined date).
You can create contracts on the consumer side, tell stubrunner where they lay (https://docs.spring.io/spring-cloud-contract/docs/current-SNAPSHOT/reference/htmlsingle/#features-stub-runner-stubs-protocol) and turn the generateStubs feature (https://docs.spring.io/spring-cloud-contract/docs/current-SNAPSHOT/reference/htmlsingle/#features-stub-runner-generate-stubs-at-runtime), example of code (https://github.com/spring-cloud-samples/spring-cloud-contract-samples/blob/master/consumer_with_latest_2_2_features/src/test/java/com/example/GenerateStubsTest.java). The problem here is that as a consumer you can write whatever you want and it might not have anything to do with reality. On the other hand you already have the contracts that you could upload to the producer side with a request that they implement their part one day.
It's up to you to decide which one you prefer, bearing in mind that each of the solutions might have its issues.
As for Pact, Pact follows the second approach since it's the consumer that defines how the interaction should look like. That again might have nothing to do with reality.
I want to pick only one consumer while running my provider side of tests not all the consumers present in PACT hasPactsFromPactBroker('http://pact-broker')
hasPactsFromPactBroker('http://pact-broker')
hasPactWith('scrape-api')
I'm not the pact-jvm maintainer but I believe there is a filter you can use. Have a look in the docs. Otherwise, just give it the URL of the one pact you want to verify. eg http://broker/pacts/provider/PROVIDER/consumer/CONSUMER/latest
I want my system to guarantee there is no data loss even if the system is shutting down.
What this mean is that the system must not miss the request message. So, I will change the way that accept http reqeust. Now, I am using http gateway/webservice gateway in spring integration. But, This isn't receive the message even if the system dies. So, I want to add the queue between the http client and the http receiver. So, I want to use a queue channel. Here is the question.
① I have to install other queue program such as activemq or rabbitmq and have to connect to the queue channel in spring integration?
② and which one is the best combination with spring integration? I heard that rabbit mq is the best one.
please give me a elaborate explanation. thanks.
First of all you description isn't clear...
If you don't want to lose messages from the QueueChannel use some Persistence MessageStore, like JdbcChannelMessageStore:
http://docs.spring.io/spring-integration/docs/latest-ga/reference/html/system-management-chapter.html#message-store
From other side there are channel wrappers for the AMQP as well as for JMS:
http://docs.spring.io/spring-integration/docs/latest-ga/reference/html/amqp.html#d4e5846
http://docs.spring.io/spring-integration/docs/latest-ga/reference/html/jms.html#jms-channel
Which really provide the same persistence durability, fault tollerant options for your use-case.
Re. activemq VS rabbitmq. I can say by my own expiriance that the last one is better, by configuration, usage from Spring Integration (Spring AMQP is under the shell). And its performance is really better.
All other info you can find in the Internet.
Please some help understanding the following:
I am using CachingConnectionFactory in my app and first used it during my jms tests to test my jms config like guaranteed delivery, rollback/commit, etc..
I am using Spring's JmsTemplate for sending and DefaultMessageListenerContainer during delivery.
I noticed that this is hard/impossible when using several test methods run sequential
Example: in test method A I throw exceptions in the Message listener (consumer side) such that retries occur.
Then test B is run and in method A I do a different test, but when I start this test I still get retry messages from test A, which I clearly not want.
I purge the Queue through jmx between tests, but still receive these retries :(...
I searched and debugged... I don't exactly understand why these retries keep comming up, even when I am sure that the purge occur correctly. Maybe it was already cached somewhere in the session... I don't know. Anybody any idea?
I found out that I needed to use the SingleConnectionFactory during testing. With this connection factory the retries disappear, but I don't really understand why. Why?
I understand that it uses only one connection (from the Spring ref), and noticed that it somehow removes the consumer after every send action, but I don't really understand what happen with these retries :(... Any idea?
(It's hard to debug because of the multi threading behavior and difficult to find good information about it on the web)
Also using CachingConnectionFactory with only one session cache size of 1 didn't solve the retry issue.
Thanks
Best bet would probably to use an embedded broker and start/stop it between each test, make sure deleteAllMessagesOnStartup is set to true and the broker should purge the store fore you, which will ensure you've got a clean slate for each test. You might also benefit from having a look at ActiveMQ's unit tests, it's a good source of examples of how the broker can be used in automated tests.
It's not an easy thing to fix: remove the messages between tests.
I tried many thingssss, like mentioned above: stop/start the broker and the class DefaultMessageListenerContainer of Spring that I use to consume my messages.
It all seem to work until I turned I set the cache level in DefaultMessageListenerContainer to Consumer such that the consumer is cached.
That is required such that the redeliveryPolicy works.
However, this messed up everything and messages where cached by DefaultMessageListenerContainer in some way, as it seemed.
At the end, I solved it by simple consuming all messages after a test (just wait a second and consume all Ok), such that the next test can begin.