Wrapping an entire request with before/after

[Zack Sampson]

Hey all,

I've wondered how to do this for years and have never quite managed to figure it out. For the purpose of metrics, I'd like to wrap a request such that I get the chance to, say, increment a counter while it runs, and then decrement it after it completes. Unlike a ContainerResponseFilter, I don't want to decrement until the body completes, if there is one.

Is there a better way to do this than by frankensteining together an interceptor and request filters?

Thank you!

Zack

[Jochen Schalanda]

Hi Zack,

you could write a Handler for Jetty, similar to the one used in Dropwizard/Dropwizard Metrics [1] to get the metrics you want.

[1]: https://github.com/dropwizard/metrics/blob/v4.1.16/metrics-jetty9/src/main/java/com/codahale/metrics/jetty9/InstrumentedHandler.java

Best regards,

Jochen

[Shawn Smith]

Alternatively, if you want to do this within Jersey and have access to all the request metadata available to a Jersey ContainerRequestFilter, you can inject Jersey's CloseableService and register a callback that will be invoked after the body completes. The callback will be invoked whether or not the request succeeds.

Here's a mockup:

import org.glassfish.jersey.server.CloseableService;

import javax.inject.Inject;
import javax.inject.Singleton;
import javax.ws.rs.container.ContainerRequestContext;
import javax.ws.rs.container.ContainerRequestFilter;
import javax.ws.rs.core.Context;
import java.io.Closeable;

@Singleton
public class TrackingFilter implements ContainerRequestFilter {
    private final CloseableService closer;

    @Inject
    public TrackingFilter(@Context CloseableService closer) {
        this.closer = closer;
    }

    @Override
    public void filter(ContainerRequestContext requestContext) {
        closer.add(startTracking(requestContext));
    }

    private Closeable startTracking(ContainerRequestContext requestContext) {
        String requestPath = requestContext.getUriInfo().getPath();
        long start = System.nanoTime();
        return () -> {
            long stop = System.nanoTime();
            System.out.println("elapsed=" + (stop - start) + " nanos,  request path=" + requestPath);
        };
    }
}

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