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

ehsavoie · 2026-01-21T15:26:05Z

/gemini review

gemini-code-assist

Code Review

This pull request introduces OpenTelemetry distributed tracing support across the A2A Java SDK client and server, along with multi-protocol support (JSONRPC, GRPC, HTTP+JSON) for the helloworld example. Key changes include adding a new a2a-java-sdk-opentelemetry module, which provides ClientTransportWrapper and CDI SpanInterceptor implementations to automatically instrument client and server operations. The ClientBuilder was enhanced to support transport wrapping, and ClientTransportConfig now includes a parameters map for passing tracing context. The helloworld example client and server were updated to demonstrate dynamic protocol selection and OpenTelemetry integration, with corresponding pom.xml and README.md changes. Review comments highlighted the need to return an unmodifiable map for ClientTransportConfig.getParameters() to ensure immutability, to use public constants for OpenTelemetry parameter keys for better maintainability, and to simplify the application.properties file by consolidating quarkus.agentcard.protocol definitions.

client/transport/spi/src/main/java/io/a2a/client/transport/spi/ClientTransportConfig.java

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

examples/helloworld/server/src/main/resources/application.properties

@trace

…d null safety Added OpenTelemetry integration for distributed tracing across the A2A SDK: - Added @trace annotation for CDI interceptors to create spans on method invocations - Created SpanInterceptor with robust CDI proxy handling supporting 5 proxy patterns - Added InvocationContext record for capturing method invocation details with: * Null safety annotations (@NonNull/@nullable) * Comprehensive JavaDoc documentation * Specific exception declarations (IllegalAccessException, InvocationTargetException) - Implemented attribute extractors for all transport types: * GrpcAttributeExtractor with null-safe gRPC context key access * JsonRPCAttributeExtractor with method name extraction * RestAttributeExtractor with conditional attribute building * RequestHandlerAttributeExtractor for default request handler - Added ClientTransportWrapper SPI for wrapping transport operations - Created OpenTelemetryClientTransport decorator supporting: * All A2A client methods (sendMessage, getTask, listTasks, etc.) * Streaming operations with event consumer wrapping * Error consumer instrumentation * Helper methods to eliminate code duplication - Updated ClientBuilder to apply transport wrappers via ServiceLoader - Added comprehensive tests for OpenTelemetryClientTransport - Added tests for SpanInterceptor CDI proxy handling - Added tests for AttributeExtractor null safety - All attribute extractors include defensive null checks preventing NPE - Updated HelloWorld example with OpenTelemetry integration: * Added OTEL dependencies and configuration * Configured trace export to console * Added README documentation for running with telemetry * Server now includes @trace annotation on agent method * Protocol can be selected - Added extras/opentelemetry module with dependencies - Updated BOM with OpenTelemetry extras - Added CDI beans.xml and ServiceLoader configuration - Updated .gitignore for IDE and build artifacts Fixes a2aproject#388 Signed-off-by: Emmanuel Hugonnet <ehugonne@redhat.com>

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

gemini-code-assist bot reviewed Nov 18, 2025

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brunobat reviewed Nov 18, 2025

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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

ehsavoie requested a review from brunobat November 20, 2025 20:41

kabir reviewed Nov 21, 2025

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kabir requested changes Nov 21, 2025

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ehsavoie force-pushed the issue_388 branch from d35543a to d5cfb1d Compare November 26, 2025 13:29

ehsavoie force-pushed the issue_388 branch 3 times, most recently from 0eee5a4 to 49b8dd0 Compare January 9, 2026 17:11

kabir reviewed Jan 12, 2026

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examples/helloworld/client/src/main/java/io/a2a/examples/helloworld/HelloWorldRunner.java Outdated Show resolved Hide resolved

client/base/src/main/java/io/a2a/client/ClientBuilder.java Outdated Show resolved Hide resolved

brunobat suggested changes Jan 12, 2026

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...as/opentelemetry/src/main/java/io/a2a/extras/opentelemetry/OpenTelemetryClientTransport.java Show resolved Hide resolved

ehsavoie force-pushed the issue_388 branch from 49b8dd0 to 076472d Compare January 16, 2026 17:51

ehsavoie added the hold label Jan 16, 2026

ehsavoie force-pushed the issue_388 branch 2 times, most recently from 0a41c0e to badca86 Compare January 21, 2026 15:15

ehsavoie requested review from brunobat, jmesnil and kabir and removed request for brunobat and fjuma January 21, 2026 15:25

gemini-code-assist bot reviewed Jan 21, 2026

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ehsavoie force-pushed the issue_388 branch from badca86 to 465ecf9 Compare January 22, 2026 09:17

ehsavoie removed the hold label Jan 22, 2026

ehsavoie requested a review from brunobat January 22, 2026 11:45

feat: Add telemetry support. #463

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feat: Add telemetry support. #463

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ehsavoie commented Nov 18, 2025

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