Documentation request: GRPC Java not compatible with Alpine Linux

[laurikimmel]

GRPC Java examples are not working on Alpine Linux since required libnetty-tcnative-boringssl-static depends on glibc. Alpine is using musl libc and application startup will fail with message similar to

io.grpc.netty.GrpcSslContexts            : netty-tcnative unavailable (this may be normal)

    java.lang.IllegalArgumentException: Failed to load any of the given libraries: [netty_tcnative_linux_x86_64, netty_tcnative_linux_x86_64_fedora, netty_tcnative_x86_64, netty_tcnative]
     	at io.netty.util.internal.NativeLibraryLoader.loadFirstAvailable(NativeLibraryLoader.java:93) ~[netty-common-4.1.27.Final.jar:4.1.27.Final]
    	at io.netty.handler.ssl.OpenSsl.loadTcNative(OpenSsl.java:440) ~[netty-handler-4.1.27.Final.jar:4.1.27.Final]
    	at io.netty.handler.ssl.OpenSsl.<clinit>(OpenSsl.java:97) ~[netty-handler-4.1.27.Final.jar:4.1.27.Final]
    	at io.grpc.netty.GrpcSslContexts.defaultSslProvider(GrpcSslContexts.java:242) [grpc-netty-1.12.0.jar:1.12.0]
    	at io.grpc.netty.GrpcSslContexts.configure(GrpcSslContexts.java:171) [grpc-netty-1.12.0.jar:1.12.0]
    	at io.grpc.netty.GrpcSslContexts.forClient(GrpcSslContexts.java:120) [grpc-netty-1.12.0.jar:1.12.0]
...

[laurikimmel]

Related issue netty/netty-tcnative#111

[anuraaga]

Thanks for the feedback. Unfortunately, as is clear in that issue, I've tried hard to fix this, including creating a fairly large PR but it doesn't seem like netty + boringssl will ever support Alpine Linux.

If you're using Java 8 I recommend distroless, which is tiny while using glibc, and hopefully there will be a good answer to GoogleContainerTools/distroless#236 for the future of Java too.

If you're using Java9+, gRPC will work without netty-tcnative as it natively supports ALPN. I don't think it should require code change, but if it does could you add the changes so we can incorporate them into the README? Thanks!