DnsNameResolverProvider not present

[SorkoPiko]

I'm losing my mind trying to fix this bug: IllegalArgumentException: Could not find a NameResolverProvider for dns://127.0.0.1:50051
For some reason, META-INF/services/io.grpc.NameResolverProvider only has one line in it:

io.grpc.netty.shaded.io.grpc.netty.UdsNameResolverProvider

So my DNS address isn't being resolved.
I'm including gRPC like this:

val grpcVersion = "1.76.0"
val protobufVersion = "4.33.0"

dependencies {
    implementation("com.google.protobuf:protobuf-java:${protobufVersion}")
    implementation("io.grpc:grpc-netty-shaded:${grpcVersion}")
    implementation("io.grpc:grpc-protobuf:${grpcVersion}")
    implementation("io.grpc:grpc-stub:${grpcVersion}")
}

tasks {
    build {
        dependsOn("shadowJar")
    }

    shadowJar {
        mergeServiceFiles()
        archiveClassifier.set("")
    }
}

Does anyone know what's wrong?
Note: this is part of a Velocity project - the issue isn't present on other implementations, however, it seems related to how gRPC is being shaded, as the ResolverProvider is missing in the compiled jar file. I've already seen #10853.

[ejona86]

You have mergeServiceFiles() which is normally the important thing you need. So it is surprising you're having trouble with the META-INF/services not finding the DNS resolver. However, I'm suspicious the problem is related to archiveClassifier.set(""). That might be causing shadowJar to use the same file names as jar, and I'm not sure what all might break. I suggest you changing the archiveClassifier of jar to something different than the empty string. I fought something like that in 2018, so you can see a comment in gRPC's build about it.

Hopefully that's it, because normally it is as easy as mergeServiceFiles() in Gradle.

[SorkoPiko]

i initially didn't have that, and it still didn't work. i think it's just an issue with Velocity, as it also uses netty, though i don't know why it would be messing it up like this at build. anyway, i ended up solving it by just adding this before i initialise my connection:

    private void registerProviders() {
        NameResolverRegistry.getDefaultRegistry()
                .register(new DnsNameResolverProvider());

        LoadBalancerRegistry.getDefaultRegistry()
                .register(new PickFirstLoadBalancerProvider());
    }

not a fix by any means, but it works.