Spring restful services in websphere

Question

Our application environment in Websphere Application Server has 3 clusters 1. UI Cluster 2. Service Cluster 3. Integration Cluster

We have around 50 war files (Micro Services) deployed to Service cluster. All services are REST based and exposed through SPRING API. Restarting Service cluster takes close to 30 mins. This time is critical during live incidents in Production. For reasons, if Service cluster needs to be restarted, we need to have 30 mins downtime for all end users. We are looking to reduce to recycle time, please suggest us for any solution.

Is there a way to load all the Spring based jar files before the application starts? i.e. for example there is a service war file called as xyz-1.0.war and there are Spring based jar files as maven dependencies. All 50 number of WAR files has the same set of dependencies, I am thinking in a way to see if we can load all the Spring based jars before the application is started by websphere server.

Please suggest.

Answer 1

If you are doing microservices then your services should be independently deployable, so they each should be in the separate cluster. Traditional WebSphere Application Server is a bit heavy weight for this solution (depending on how many resources you have on your nodes), so I'd suggest you to migrate your service cluster to WebSphere Liberty and in that case you could have each service in separate clusters. This would allow you to restart each service independently, at much shorter time.

If you are doing microservices, then your UI cluster should be prepared for any service unavailability - that is a primer when doing microservices, and display some message to end user, that this service is temporary unavailable.

Regarding your current setup - you could try the "Rollout update" option, which will restart your server sequentially, so services should be available on other nodes.

so-random-dude advice to use blue/green deployment is also very good. You could have 2 cells, and then switch plugin configuration after redeployment. If your services are written in a way that different versions can run in parallel during update, you would have no downtime.

If you want to reduce downtime further and improve performance, you should consider using Java EE/Rest services instead of Spring, as it will cut down significantly size of your app, amount of libs to be scanned, deployment and startup time. It is much better integrated and supported in WebSphere Liberty than tons of jars that you have to include with Spring.

Answer 2

I have a simple solution for you, just ditch the Websphere and deploy those 50 "wars" as independent jars with embedded netty/undertow/tomcat/jetty in it.

I am afraid, what you have currently is not at all a microservice architecture. Agreed, different teams/consultants/organizations has different interpretation of "micro"services. But this is an extreme, which you should avoid at any cost; because you are having all the pain points of microservice and ZERO benefits (benefits such as independent scalability/deployability etc).

Restarting Service cluster takes close to 30 mins. This time is critical during live incidents in Production. For reasons, if Service cluster needs to be restarted, we need to have 30 mins downtime for all end users

Have you looked at different deployment strategies like Canary deployment / Blue-Green deployment? Do you have more than one instances behind a load balancer?

Answer 3

I don't know that you can load them BEFORE the application starts (class loading is generally on-demand), but you might be able to speed things up through the use of shared libraries for your common files, so they'd be loaded by a single class loader rather than from each WAR's class loader. It won't eliminate the class loading activity, since each WAR would still need to load the necessary classes, but it'd speed up the mechanics of the class loads since the shared library loader would return the already-loaded class rather than searching its class path.

There are two different approaches you could take to this. Step one in both cases is to create a shared library with the classes that are shared among the applications. The options for step two:

1) Create a custom class loader on the server and associate the shared library with this new class loader. This will make the classes in the shared library visible to all applications running on the server.

2) In the shared library configuration, select "Use an isolated class loader for this shared library", then associate the shared library with any applications that require it. In the event that the shared classes are required only by some applications, this will provide them only to the applications that require them.

A couple points of caution:

• If you require unique Class instances (for example, static values unique to each WAR), this approach won't work, because there will be only one instance of the Class loaded by the shared library loader. In that event, you'll have to stick with WAR-level packaging.
• If you use the isolated class loader solution, note that those loaders use "parent last" class loading, in which they are searched before server class loaders. If you have anything in those libraries that conflicts with classes provided by the server, it could open you up to ClassCastExceptions or LinkageErrors.
• Note that the shared library loaders operate as parents of the WAR loaders, and as such, classes in the libraries will not be able to "see" classes in the WARs. You'll need to make sure that the libraries are essentially self-contained in order for these approaches to be successful.

More specific details on the configuration steps can be found in this blog post: https://www.ibm.com/developerworks/community/blogs/aimsupport/entry/create_shared_library_and_associate_it_with_the_application_server_or_application_on_websphere_application_server?lang=en_us