Grpc-java: Need lots more examples

[ejona86]

This is intended to be a dumping ground for the moment.

waitForReady
channel state API to pre-connect
example NameResolver (with SPI) (both polling and non-polling)
channel/server.executor()
auth (custom client-side and server-side verification)

[ejona86]

custom TLS, with our testing certificates (can include comments to say what's unnecessary using normal CAs)
Mutual auth TLS, also with our testing certs

[hsyed]

Some feedback for what is missing from my experience:

More examples covering the ins and outs of wiring up Interceptors, and the mechanics of Context and tracing. I'm going by trial and error to achieve the patterns I can with go-grpc.

---

Basic Tracing is not configured out of the box.

I am assuming that tracing is meant to setup instrumentation similar to go-grpc when debug / event support is turned on. At least thats what I get from looking through the code and tests. I've had to manually setup everything up to zpages.

Our build is setup in Bazel, I'm quite sure I am not missing any dependencies. This is what I have done so far, I cannot contribute to the span once I leave the interceptor -- I assume I have to thread the span id through the Context ?

Tracing.getTraceConfig().updateActiveTraceParams(TraceParams.DEFAULT.toBuilder().setSampler(Samplers.alwaysSample()).build());
        Tracing.getExportComponent().getSampledSpanStore().registerSpanNamesForCollection(
                PciServiceGrpc.getServiceDescriptor().getMethods().stream().map(m -> m.getFullMethodName()).collect(Collectors.toList())
        );

        // Setup the zpages
        ZPageHandlers.startHttpServerAndRegisterAll(8090);

 .intercept(new ServerInterceptor() {
                    @Override
                    public <ReqT, RespT> ServerCall.Listener<ReqT> interceptCall(ServerCall<ReqT, RespT> serverCall, Metadata metadata, ServerCallHandler<ReqT, RespT> serverCallHandler) {
                        MDC.clear();
                        MDC.put("grpc.method", serverCall.getMethodDescriptor().getFullMethodName());
                        final Map<String, String> mdcContext = MDC.getCopyOfContextMap();

                        final Span tracingSpan = Tracing.getTracer().spanBuilder(serverCall.getMethodDescriptor().getFullMethodName()).startSpan();

                        final ServerCall<ReqT, RespT> forwardedServerCall = new ForwardingServerCall.SimpleForwardingServerCall(serverCall) {
                            @Override
                            public void sendMessage(Object o) {
                                MDC.setContextMap(mdcContext);
                                super.sendMessage(o);
                                tracingSpan.end();
                            }

                            @Override
                            public void close(Status status, Metadata metadata) {
                                MDC.setContextMap(mdcContext);
                                super.close(status, metadata);
                                if(status.isOk()) {
                                    tracingSpan.end();
                                } else {
                                    tracingSpan.end(EndSpanOptions.builder().setStatus(io.opencensus.trace.Status.INTERNAL).build());
                                }
                            }
                        };

                        return new ForwardingServerCallListener.SimpleForwardingServerCallListener<ReqT>(serverCallHandler.startCall(forwardedServerCall, metadata)) {
                            @Override
                            public void onMessage(ReqT o) {
                                MDC.setContextMap(mdcContext);
                                super.onMessage(o);
                            }
                        };
                    }
                });

[hsyed]

Update: wiring up Contexts.interceptCall and using the span context ContextUtils.CONTEXT_SPAN_KEY to thread the span through the context did the trick. Looking forward to some examples showing the right way to do things.

[ejona86]

Context example, explaining auto-propagation of deadlines and cancellation, with mention of fork().

[ensonic]

Any doc explaining the interaction when using a set of grpc services and calling one from another would be helpful. When should I create a new context. When do I need a new thread (especially if a sync call will do an async call).

[ejona86]

How to fail a call from a ServerInterceptor (in short: don't throw!)

[Entea]

a bump up.

[mkobit]

Relationships between:

• ServerInterceptor
• ServerCall
• ServerCall.Listener
• ServerCallHandler

[magpor]

So is there an explanation for the relationship between

ServerInterceptor
ServerCall
ServerCall.Listener
ServerCallHandler

In an easy to read documentation

[sanjaypujare]

In the grpc.io google group: https://groups.google.com/g/grpc-io/c/cGGNp-Ss0V0/m/WjkI51GqCAAJ

Also there is an article https://eng.revinate.com/2017/11/07/grpc-spring-security.html that has some explanation you are looking for.