Power support

[npanpaliya]

Changes required to build grpc-java on ppc64le architecture.

After making these changes, grpc-java still fails for netty-tcnative jar not being available for ppcle_64. So, I built netty-tcnative from source on my system and made grpc-java to point to that. After this, ./gradlew build command does complete successfully.
For netty-tcnative jar, I've requested netty community to publish a jar for ppcle_64 arch on maven's central repository. netty/netty-tcnative#194.

I've also verified my changes on x86_64 platform to ensure nothing breaks there.

[grpc-kokoro]

Thanks for your pull request. The automated tests will run as soon as one of the admins verifies this change is ok for us to run on our infrastructure.

[npanpaliya]

Also a note, in order to build grpc-java on ppc64le arch, one would need to build protobuf from tag 3.0.2 and protoc-gen-javalite from v3.0.0-javalite tag. And then build grpc-java as -
./gradlew build -Pprotoc=/usr/local/bin/protoc -Pprotoc-gen-javalite=/usr/local/bin/protoc-gen-javalite

[ejona86]

This is functionally equivalent to the patch I posted in #2202 (comment) . My patch should fix most of the various non-x86 platforms. The only thing is that it won't allow cross-compiling or choosing to use 32 bit on a 64 bit machine.

Would you mind testing it and confirming that it works for powerpc?

[npanpaliya]

Thanks @ejona86 .
I'll surely verify and confirm this to you.

[npanpaliya]

Hi @ejona86 ,
I tried your PR but it still gives me error as below -

$ ./gradlew build -Pprotoc=/usr/local/bin/protoc -Pprotoc-gen-javalite=/usr/local/bin/protoc-gen-javalite
*** Building codegen requires Protobuf version 3.0.0-beta-3
*** Please refer to https://github.com/grpc/grpc-java/blob/master/COMPILING.md#how-to-build-code-generation-plugin

FAILURE: Build failed with an exception.

* What went wrong:
A problem occurred configuring project ':grpc-compiler'.
> Exception thrown while executing model rule: NativeComponentModelPlugin.Rules#createBinaries
   > Invalid NativePlatform: ppcle_64

[npanpaliya]

Hi @ejona86, As the older PR of yours doesn't seem to server our purpose for Power, could you please consider my PR for merging?

[ejona86]

@npanpaliya, I don't really believe the test results you provided; I feel like something else was in play. The problem is I will likely quickly break the support if I don't understand why my changes failed to work, because I want to refactor that part of the script.

[ejona86]

retest this please (this is for Jenkins)

[carl-mastrangelo]

@npanpaliya This PR is probably fine, but gRPC team doesn't have the powerpc hardware to make this always works. If this is submitted, please be aware we may break this in the future.

Aside from that generally LGTM.