feat: Add telemetry support. #463

ehsavoie · 2025-11-18T15:54:42Z

Adding support for OpenTelemetry

Fixes #388 🦕

gemini-code-assist · 2025-11-18T15:55:20Z

Summary of Changes

Hello @ehsavoie, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request integrates OpenTelemetry into the A2A Java SDK, providing robust distributed tracing capabilities. The changes enable automatic span creation for both client-initiated and server-processed A2A requests, offering deeper visibility into the flow of operations. This enhancement is crucial for monitoring, troubleshooting, and understanding the performance characteristics of applications built with the SDK.

Highlights

OpenTelemetry Module: Introduced a new Maven module, extras/opentelemetry, to encapsulate all OpenTelemetry integration logic for the A2A Java SDK.
Client-Side Tracing: Implemented dynamic wrapping of ClientTransport instances with OpenTelemetryClientTransport within the ClientBuilder. This allows for automatic tracing of client-side A2A interactions when an OpenTelemetry Tracer is provided in the ClientTransportConfig.
Server-Side Tracing Interceptors: Added a new @Trace annotation and SpanInterceptor mechanism to enable automatic distributed tracing for server-side request handler methods across gRPC, JSON-RPC, and REST protocols. Custom AttributeExtractor implementations are used to enrich spans with relevant request details.
Enhanced ClientTransportConfig: The ClientTransportConfig now includes a generic parameters map, facilitating the injection of arbitrary configuration, such as the OpenTelemetry Tracer instance, into transport implementations.
Example Application Updates: The helloworld example client and server applications have been updated to demonstrate the setup and usage of OpenTelemetry, including dependency additions and configuration for tracing.

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gemini-code-assist

Code Review

This pull request adds support for OpenTelemetry, which is a great addition for observability. The implementation introduces a new opentelemetry extras module and integrates tracing on both the client and server sides. On the client side, it uses reflection for optional wrapping, and on the server side, it uses CDI interceptors with a new @Trace annotation. My review focuses on improving the robustness and maintainability of this new feature. I've found a few critical issues, such as a ClassCastException in an attribute extractor and silent exception swallowing that could make debugging difficult. I've also identified several opportunities for code cleanup, such as fixing typos, removing duplicated code, and improving the design of the CDI interceptor to better support dependency injection. Addressing these points will make the OpenTelemetry integration more solid and easier to maintain.

transport/rest/src/main/java/io/a2a/transport/rest/handler/RestAttributeExtractor.java

client/base/src/main/java/io/a2a/client/ClientBuilder.java

...as/opentelemetry/src/main/java/io/a2a/extras/opentelemetry/OpenTelemetryClientTransport.java

extras/opentelemetry/src/main/java/io/a2a/extras/opentelemetry/SpanInterceptor.java

...as/opentelemetry/src/main/java/io/a2a/extras/opentelemetry/OpenTelemetryClientTransport.java

extras/opentelemetry/src/main/java/io/a2a/extras/opentelemetry/SpanInterceptor.java

transport/grpc/src/main/java/io/a2a/transport/grpc/handler/GrpcHandler.java

transport/grpc/src/main/java/io/a2a/transport/grpc/handler/GrpctAttributeExtractor.java

brunobat

I think you need to decide if you are creating your own instrumentation annotations and API or if you just reuse the ones provided by OTel.

Also, the attribute names, should follow these semantic conventions, as much as possible: https://opentelemetry.io/docs/specs/semconv/gen-ai/gen-ai-agent-spans/

server-common/src/main/java/io/a2a/server/interceptors/Trace.java

server-common/src/main/java/io/a2a/server/interceptors/AttributeExtractor.java

server-common/src/main/java/io/a2a/server/interceptors/Kind.java

...as/opentelemetry/src/main/java/io/a2a/extras/opentelemetry/OpenTelemetryClientTransport.java

examples/helloworld/client/src/main/java/io/a2a/examples/helloworld/HelloWorldClient.java

kabir

A few things which may or may not be needed :-)

client/base/src/main/java/io/a2a/client/ClientBuilder.java

extras/opentelemetry/src/main/java/io/a2a/extras/opentelemetry/SpanInterceptor.java

server-common/src/main/java/io/a2a/server/requesthandlers/RequestHandlerAttributeExtractor.java

transport/grpc/src/main/java/io/a2a/transport/grpc/handler/GrpcAttributeExtractor.java

transport/jsonrpc/src/main/java/io/a2a/transport/jsonrpc/handler/JSONRPCAttributeExtractor.java

transport/rest/src/main/java/io/a2a/transport/rest/handler/RestAttributeExtractor.java

kabir

Actually, @ehsavoie it looks like you are adding Otel tracing to the example. But I don't know how to enable this etc.
Can you update the README with instructions?

Maybe we could also make this example testable in the CI, like we do for the cloud-deployment one?

Also, it would be good to have some tests in the extras module

kabir

@ehsavoie 2 small things.

If the JBang validator is tricky, open an issue and link it here

examples/helloworld/client/src/main/java/io/a2a/examples/helloworld/HelloWorldRunner.java

client/base/src/main/java/io/a2a/client/ClientBuilder.java

...as/opentelemetry/src/main/java/io/a2a/extras/opentelemetry/OpenTelemetryClientTransport.java

client/base/src/main/java/io/a2a/client/ClientBuilder.java

...as/opentelemetry/common/src/main/java/io/a2a/extras/opentelemetry/A2AObservabilityNames.java

server-common/src/main/java/io/a2a/server/interceptors/A2AObservabilityNames.java

server-common/src/main/java/io/a2a/server/requesthandlers/RequestHandlerAttributeExtractor.java

transport/grpc/src/main/java/io/a2a/transport/grpc/context/GrpcContextKeys.java

transport/rest/src/main/java/io/a2a/transport/rest/handler/RestAttributeExtractor.java

examples/helloworld/server/pom.xml

Out of date

kabir · 2026-01-27T15:03:57Z

/gemini review

gemini-code-assist

Code Review

This pull request introduces comprehensive OpenTelemetry support across the client and server components, including gRPC, JSON-RPC, and REST transports. The implementation leverages a flexible wrapper pattern for clients and CDI interceptors for servers, allowing for extensible tracing. Attribute extraction is thoughtfully tailored to each transport and method, providing rich and detailed tracing information. The accompanying documentation and tests have been updated to reflect these new capabilities, ensuring clarity and correctness. Overall, the changes are well-implemented and significantly enhance the observability of the A2A SDK.

examples/helloworld/server/src/main/java/io/a2a/examples/helloworld/AgentCardProducer.java

ehsavoie · 2026-02-04T12:17:11Z

/gemini review

gemini-code-assist

Code Review

This pull request introduces comprehensive OpenTelemetry support for both client and server components. The implementation is well-designed, using a ServiceLoader-based ClientTransportWrapper for the client and CDI interceptors for the server, which allows for clean, decoupled observability. The example applications have been updated to demonstrate how to enable and use this new telemetry feature. The changes are extensive and well-executed. I've found a couple of minor issues: a potential resource leak in the client example due to an incorrectly placed finally block, and a small typo in the README documentation. Overall, this is a great addition to the SDK.

examples/helloworld/client/src/main/java/io/a2a/examples/helloworld/HelloWorldClient.java

examples/helloworld/client/README.md

...elemetry/integration-tests/src/test/java/io/a2a/extras/opentelemetry/it/OpenTelemetryIT.java

Adds OpenTelemetry integration for distributed tracing: - Client: OpenTelemetryClientTransport decorator wrapping all client operations with span creation and context propagation via ClientTransportWrapper SPI - Server: OpenTelemetryRequestHandlerDecorator CDI decorator for request handlers - Common: A2AObservabilityNames for standard observability attributes - Integration tests with comprehensive coverage for client and server tracing - Updated HelloWorld examples with OTEL configuration and documentation Fixes a2aproject#388 Signed-off-by: Emmanuel Hugonnet <ehugonne@redhat.com>

kabir · 2026-02-11T13:59:52Z

...2a/extras/opentelemetry/client/propagation/OpenTelemetryClientPropagatorTransportWapper.java

+ * ));
+ * }</pre>
+ */
+public class OpenTelemetryClientPropagatorTransportWapper implements ClientTransportWrapper {


s/Wapper/Wrapper

kabir · 2026-02-11T14:00:34Z

.gitignore

 .serena/
 .bob/
 claudedocs
+.bob/


Already on line 59

kabir · 2026-02-11T14:01:36Z

.gitignore


 # NetBeans
 nb-configuration.xml
+nbactions.xml


There is another NetBeans section further down, which also has this file

kabir · 2026-02-11T14:03:45Z

spec/src/main/java/io/a2a/spec/Message.java

    }

+    @Override
+    public String toString() {


Concern:

Records auto-generate toString() - explicitly overriding changes public API behavior

Used for span attributes when extractRequest/extractResponse flags enabled

Consider if this is the right approach for observability data extraction

Recommendation: Document this as intentional API change, or use separate utility method for telemetry formatting

kabir · 2026-02-11T14:03:54Z

spec/src/main/java/io/a2a/spec/Task.java

    }

+    @Override
+    public String toString() {


Same as for Message

kabir · 2026-02-11T14:04:32Z

...2a/extras/opentelemetry/client/propagation/OpenTelemetryClientPropagatorTransportWapper.java

+import io.opentelemetry.api.trace.Tracer;
+
+/**
+ * OpenTelemetry client transport wrapper that adds opentelemtry propagation to A2A client calls.


"adds opentelemetry"

ehsavoie requested review from fjuma and kabir November 18, 2025 15:54

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ehsavoie force-pushed the issue_388 branch 4 times, most recently from 7661dd6 to 893ce8b Compare November 20, 2025 13:57

ehsavoie changed the title ~~Issue 388~~ feat: Add telemetry support. Nov 20, 2025

ehsavoie force-pushed the issue_388 branch 2 times, most recently from 22a2af4 to d35543a Compare November 20, 2025 14:46

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feat: Add telemetry support. #463

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ehsavoie commented Nov 18, 2025

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