新增对ServiceConfig配置的支持

[wushengju]

1.新增之后需要进行如下所示的配置
grpc.client.tcl-cloud-provider.retry-enabled=true grpc.client.tcl-cloud-provider.method-config[0].name[0].service=helloworld.Greeter grpc.client.tcl-cloud-provider.method-config[0].name[0].method=SayHello grpc.client.tcl-cloud-provider.method-config[0].retry-policy.max-attempts=3 grpc.client.tcl-cloud-provider.method-config[0].retry-policy.initial-backoff=1 grpc.client.tcl-cloud-provider.method-config[0].retry-policy.max-backoff=1 grpc.client.tcl-cloud-provider.method-config[0].retry-policy.backoff-multiplier=2 grpc.client.tcl-cloud-provider.method-config[0].retry-policy.retryable-status-codes=UNKNOWN,UNAVAILABLE
2.测试结果如下

---

EDIT by @ST-DDT

English

References:

• https://github.com/grpc/proposal/blob/master/A6-client-retries.md
• https://github.com/grpc/grpc-java/blob/master/core/src/main/java/io/grpc/internal/RetryPolicy.java

[ST-DDT]

Thanks for your contribution.

There are some small changes I would like to see before merging this. See my comments for details.
Also please run ./gradle spotlessApply before committing.
Lastly, please add a test that ensures this works as expected and does not break unnoticed in a future release.

If you need help with any of these, feel free to ask me and I will try to help you.

[wushengju]

Thanks for your contribution.

There are some small changes I would like to see before merging this. See my comments for details.
Also please run ./gradle spotlessApply before committing.
Lastly, please add a test that ensures this works as expected and does not break unnoticed in a future release.

If you need help with any of these, feel free to ask me and I will try to help you.

I have settled your proposal and also add GrpcChannelPropertiesGivenMethodConfigUnitTest for test

[ST-DDT]

I'll try to add some integration tests that actually test, that the retry/service config is working.
Maybe I can also tweak the datatypes a bit to simplify the configuration some more.

[wushengju]

I'll try to add some integration tests that actually test, that the retry/service config is working.
Maybe I can also tweak the datatypes a bit to simplify the configuration some more.

Ok just do it

[ST-DDT]

I pushed the first part and will hopefully finish it in the next few days.

TODO for me: Check whether the config metadata will be generated by spring.

[ST-DDT]

To avoid conflicts with other values in the serviceConfig it might be neccessary to wrap the methodConfig property in a defaultServiceConfig property for clarity.

[ST-DDT]

The default service config might be used outside of the retry logic.
So it might be neccessary to move it "elsewhere".