Expose ServiceLocator from JerseyHandlerFilter

[Limess]

• Framework version: 1.0.0
• Implementations: Jersey

Scenario

I wish to access the org.glassfish.hk2.api.ServiceLocator instance from the JerseyHandlerFilter object, this is so I can eagerly instantiate services in response to a scheduled warm up event (e.g. via https://github.com/FidelLimited/serverless-plugin-warmup).

Example

This stackoverflow answer provides an example of expected access using a ContainerLifecycleListener, although I believe if jersey is exposed from JerseyHandlerFilter this would be accessible from RequestStreamHandler.handleRequest.

[sapessi]

Hey @Limess, You should be able to follow the StackOverflow example to the Letter. When you initialize the JerseyLambdaContainerHandler, you pass in a JAX-RS Application object, which ResourceConfig is an implementation of. Just like in the example from StackOverflow, you should be able to create your own version of ResourceConfig to customize the ContainerLifecycleListener. Let me know if this works for you.

I will keep this issue open anyway to explore other ways to expose the ContainerLifecycleListener for the next release.

[Limess]

Hi @sapessi, my mistake - the getServiceLocator method was removed in Jersey 2.26, I'll see if I can find any alternative means of accessing it outside of a Feature. Feel free to close this if it doesn't serve any purpose!

Would you have any other idea how I could instantiate my hk2 resources based on a simple JSON event, without having a specific handler/filter? (I only want to do this eagerly on certain async events, not user facing requests)

[sapessi]

Can you give me an example of the kind of resources you are trying to load? do you just want to load everything at the start?

[Limess]

@sapessi the scenario I would like:

• Normal HTTP request comes in via API gateway, needed dependencies are loaded on the request as singletons via hk2. This is my current situation, e.g.

bindFactory(AWSKMSFactory.class).to(AWSKMS.class).in(Singleton.class);

Most of the dependencies are AWS API classes for Dynamo, SES, Kinesis, KMS, but a few get configuration asynchronously upon construction.

• Warmup event from direct lambda invocation (not API gateway). This would ideally load all dependencies (i.e. the same behaviour as using Immediate.class). This event would need to work on all routes. I'm currently handling this event using:

ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
IOUtils.copy(inputStream, byteArrayOutputStream);
byte[] bytes = byteArrayOutputStream.toByteArray();

LambdaEvent event = JerseyLambdaContainerHandler.getObjectMapper()
                    .readerFor(LambdaEvent.class)
                    .readValue(bytes);
if(event.isWarmupEvent()) { // handle loading of dependencies }
else {
   handler.proxyStream(new ByteArrayInputStream(bytes), outputStream, context);
}

but have no way I can think of of forcing hk2 to instantiate all unloaded dependencies then.

The use case for this is wanting to use a generic plugin to keep at least 1 instance of our lambdas warm so as not to suffer cold start overhead for sparse usage, while minimising startup time of new containers being consumed via API Gateway.

[sapessi]

Thanks for the info @Limess - now I get what you are trying to do. Let me look into it today and I'll let you know something here.

[sapessi]

After looking into this some more, I don't think there's anything we need to do here for Jersey 2.26.