Add support for java's jdk.httpserver module

[SentryMan]

Is your feature request related to a problem? Please describe.

Currently, there is no support for the humble jdk.httpserver.

Describe the solution you'd like

A new instrumentation should be added

Describe alternatives you've considered

No response

Additional context

Since Java 21, virtual threads allow for some decent performance using this server, so it would be nice if we could have native instrumentation.

[laurit]

We'd welcome a contribution for this.

[SentryMan]

I see, what resources would you recommend in order for me to gain the knowledge required to implement? Or should I try to copy an existing impl like jetty and try to reverse engineer?

[trask]

hi @SentryMan! there are some good resources linked under https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/main/CONTRIBUTING.md

in particular https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/main/docs/contributing/writing-instrumentation.md

[laurit]

Or should I try to copy an existing impl like jetty and try to reverse engineer?

I think jetty isn't the best choice to copy from as it only has the agent instrumentation and it interacts with servlet instrumentation. You could start from https://github.com/open-telemetry/opentelemetry-java-instrumentation/tree/main/instrumentation/armeria/armeria-1.3/library
We provide 2 kinds of instrumentations, the agent instrumentation that is in the javaagent directory and manual instrumentation libraries that can be used without agent by including the library in your application. The manual instrumentation libraries are in the library directory. It should be easier to start with the manual instrumentation library as this is just plain java without bytecode modifications. Unfortunately building the library instrumentation isn't always feasible. So one of the first decisions should be deciding whether you can build one. Here I think you can build one using a https://docs.oracle.com/en/java/javase/23/docs/api/jdk.httpserver/com/sun/net/httpserver/Filter.html You can copy paste most of the stuff. The parts you need to implement are https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/main/instrumentation/armeria/armeria-1.3/library/src/main/java/io/opentelemetry/instrumentation/armeria/v1_3/internal/RequestContextGetter.java This class is used to read request headers, used for context propagation. https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/main/instrumentation/armeria/armeria-1.3/library/src/main/java/io/opentelemetry/instrumentation/armeria/v1_3/internal/ArmeriaHttpServerAttributesGetter.java span/metric attributes are filled based on the info from this class. If some info is not available you can return null.

opentelemetry-java-instrumentation/instrumentation/armeria/armeria-1.3/library/src/main/java/io/opentelemetry/instrumentation/armeria/v1_3/ArmeriaServerTelemetry.java

Line 39 in 99267fe

public Function<? super HttpService, ? extends HttpService> newDecorator() {

this method sets up the tracing, it is framework specific. You probably could return a filter that does the tracing. Have a look at other ServerTelemetry classes to gather ideas. For testing use https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/main/instrumentation/armeria/armeria-1.3/library/src/test/java/io/opentelemetry/instrumentation/armeria/v1_3/ArmeriaHttpServerTest.java