Provide ability to add HTTP server response headers, with Tomcat implementation #7990
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...pi/src/main/java/io/opentelemetry/javaagent/bootstrap/http/HttpServerResponseCustomizer.java
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.../main/java/io/opentelemetry/javaagent/bootstrap/http/HttpServerResponseCustomizerHolder.java
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.../main/java/io/opentelemetry/javaagent/bootstrap/http/HttpServerResponseCustomizerHolder.java
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...in/java/io/opentelemetry/javaagent/instrumentation/tomcat/v10_0/Tomcat10ResponseMutator.java
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| @CanIgnoreReturnValue | ||
| public HttpServerTestOptions setHasResponseCustomizer( | ||
| Predicate<ServerEndpoint> hasResponseCustomizer) { | ||
| this.hasResponseCustomizer = hasResponseCustomizer; |
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Is there really a need for a Predicate? Is there any scenario where a boolean wouldn't work?
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This can be useful in cases where there is no specific support for an appserver directly, so some built-in error pages might not be handled, but we still expect the servlet fallback to handle it for most endpoints.
...r/src/main/java/io/opentelemetry/javaagent/testing/http/TestAgentHttpResponseCustomizer.java
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I think this PR resolves #5353 the best way we can - since there is no standard (yet) for returning the trace information in HTTP server response, we let users implement it by themselves via extensions. |
mateuszrzeszutek
approved these changes
Mar 9, 2023
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This allows custom distributions of the agent to register
HttpServerResponseCustomizerimplementations. When a supported HTTP server instrumentation starts processing a response, theonStartmethod of all registered implementations will be invoked with theContextof the SERVER span, an instrumentation-specific response object andHttpServerResponseMutatorinstance that allows appending headers to that response.The intent of this is to allow custom distributions to set a header containing span context information, such as the trace and span IDs. As such, the initial implementation only allows appending response headers and nothing else.
The
HttpServerResponseCustomizerand related classes are currently in a subpackage of theio.opentelemetry.javaagent.bootstrappackage injavaagent-extension-api. This makes them get loaded in the bootstrap classloader, thus directly accessible from instrumentations. I am not aware if there is an elegant way to put it in the agent classloader instead, yet have the same instance accessible from bothAgentInstallerand instrumentations.This also includes Tomcat-specific implementation in order to be able to demonstrate that it works, and add automated testing of this to HttpServerTest including one implementation.