net.devh.boot.grpc.client.nameresolver.DiscoveryClientNameResolver No servers found for cloudtrace.googleapis.com

[quan-nh]

The context

I have an app with these dependencies.

    implementation 'net.devh:grpc-client-spring-boot-starter:2.6.0.RELEASE'
    implementation 'org.springframework.cloud:spring-cloud-starter-sleuth'
    implementation 'io.zipkin.brave:brave-instrumentation-grpc:5.9.1'
    implementation 'org.springframework.cloud:spring-cloud-gcp-starter-logging'
    implementation 'org.springframework.cloud:spring-cloud-gcp-starter-trace'

The app run on GCP & I want to use gcp trace, follow this guide https://codelabs.developers.google.com/codelabs/cloud-spring-cloud-gcp-trace/index.html.

The question

net.devh.boot.grpc.client.nameresolver.DiscoveryClientNameResolver class show this error(?)
No servers found for cloudtrace.googleapis.com & no trace is recorded in Stackdriver Trace. The Stackdriver Trace API is already enabled, so I thing maybe there is a conflict with spring-cloud-gcp-starter-trace library (as cloudtrace should be handled by that lib, not grpc client)?

Stacktraces and logs

The application's environment

Which versions do you use?

• Spring (boot): 2.2.1.RELEASE
• grpc-java: 1.25.0
• grpc-spring-boot-starter:2.6.0.RELEASE
• java: 11 (64bit)

Additional information

• Did it ever work before?
• How can we reproduce it?
• Do you have a demo?

[ST-DDT]

AFAICT the most likely cause of this issue is that cloudtrace.googleapis.com fails to specify a schema and thus on how to resolve that target/name.
Grpcs dns resolver has a prio of 5 , which is the default in plain grpc. But if a discovery client (prio 6) is present in springs application context, then grpc will use that one instead.

See also
https://yidongnan.github.io/grpc-spring-boot-starter/en/client/configuration#choosing-the-target
And
https://github.com/yidongnan/grpc-spring-boot-starter/issues/300

[quan-nh]

I think this is what spring-cloud-gcp-starter-trace do related to this issue https://github.com/spring-cloud/spring-cloud-gcp/blob/master/spring-cloud-gcp-autoconfigure/src/main/java/org/springframework/cloud/gcp/autoconfigure/trace/StackdriverTraceAutoConfiguration.java

Do you have any suggestion on fixing this issue?

[ST-DDT]

https://github.com/spring-cloud/spring-cloud-gcp/blob/master/spring-cloud-gcp-autoconfigure/src/main/java/org/springframework/cloud/gcp/autoconfigure/trace/StackdriverTraceAutoConfiguration.java#L143

- return ManagedChannelBuilder.forTarget("cloudtrace.googleapis.com")
+ return ManagedChannelBuilder.forTarget("dns:///cloudtrace.googleapis.com")

So until they change it upstream, you can add the following bean def to your application config:

@Bean(destroyMethod = "shutdownNow")
public ManagedChannel stackdriverSenderChannel() {
    return ManagedChannelBuilder.forTarget("dns:///cloudtrace.googleapis.com")
            .userAgent(new UserAgentHeaderProvider(StackdriverTraceAutoConfiguration .class).getUserAgent())
            .build();
}

[ST-DDT]

I created a PR at grpc-java that details the usage expectations of the MangagedChannelBuilder#forTarget(String) method. Once that is merged I will create PRs for the libraries that fail to specify the dns scheme themselves.

[ST-DDT]

I created a PR over at GCP that will fix this issue:
spring-attic/spring-cloud-gcp#2085