[grpc-java] Get custom method option from interceptors

[ran...@addepar.com]

What's the best way to get custom method option data (https://developers.google.com/protocol-buffers/docs/proto3#custom_options) from server interceptors?

[Josh Humphries]

I'm guessing you are interested in doing this with Java (since I see "[grpc-java]" in the subject).

You can query the grpc ServiceDescriptor for its "schema descriptor". For proto-generated services, this will be a ProtoFileDescriptorSupplier, that provides access to the FileDescriptor, which in turn contains everything you're looking for.

The slight trick is that the interceptor, with each call, only sees a MethodDescriptor for the method being invoked, which does not appear to have a reference back to its enclosing ServiceDescriptor. So you'd need to construct a "sidecar" map that allows access to the service descriptors from the interceptor(s).

Here's a gist that demonstrates this: https://gist.github.com/jhump/e8f67087ec5a3918f7b270a4a2b83516 (the sidecar map is the MethodOptionsRegistry).

(Word of warning: I have not tried to actually compile and run the gist, so you may find some small errors. But it should at least be instructive in showing everything you actually need.)

----
Josh Humphries
jh...@bluegosling.com

On Tue, Jul 18, 2017 at 1:40 PM, ran.bi via grpc.io <grp...@googlegroups.com> wrote:

What's the best way to get custom method option data (https://developers.google.com/protocol-buffers/docs/proto3#custom_options) from server interceptors?

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[Ran Bi]

Thanks, Josh. It is helpful!

On Wed, Jul 19, 2017 at 7:28 AM Josh Humphries <jh...@bluegosling.com> wrote:

I'm guessing you are interested in doing this with Java (since I see "[grpc-java]" in the subject).

You can query the grpc ServiceDescriptor for its "schema descriptor". For proto-generated services, this will be a ProtoFileDescriptorSupplier, that provides access to the FileDescriptor, which in turn contains everything you're looking for.

The slight trick is that the interceptor, with each call, only sees a MethodDescriptor for the method being invoked, which does not appear to have a reference back to its enclosing ServiceDescriptor. So you'd need to construct a "sidecar" map that allows access to the service descriptors from the interceptor(s).

Here's a gist that demonstrates this: https://gist.github.com/jhump/e8f67087ec5a3918f7b270a4a2b83516 (the sidecar map is the MethodOptionsRegistry).

(Word of warning: I have not tried to actually compile and run the gist, so you may find some small errors. But it should at least be instructive in showing everything you actually need.)

----
Josh Humphries
jh...@bluegosling.com

On Tue, Jul 18, 2017 at 1:40 PM, ran.bi via grpc.io <grp...@googlegroups.com> wrote:

What's the best way to get custom method option data (https://developers.google.com/protocol-buffers/docs/proto3#custom_options) from server interceptors?

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[Eric Anderson]

https://github.com/grpc/grpc-java/pull/3086 will add the details to gRPC's MethodDescriptor as well. It also adds ProtoServiceDescriptorSupplier and ProtoMethodDescriptorSupplier for convenience. (The schema object in the service implements the file and service descriptor suppliers, the schema object in the method implements all three.)

It looks like the review stalled. I've poked it. Since it adds an API used by the generated code we can't mark the API ExperimentalApi, so it required a heavier amount of review.

On Wed, Jul 19, 2017 at 10:30 AM, 'Ran Bi' via grpc.io <grp...@googlegroups.com> wrote:

Thanks, Josh. It is helpful!

On Wed, Jul 19, 2017 at 7:28 AM Josh Humphries <jh...@bluegosling.com> wrote:

I'm guessing you are interested in doing this with Java (since I see "[grpc-java]" in the subject).

You can query the grpc ServiceDescriptor for its "schema descriptor". For proto-generated services, this will be a ProtoFileDescriptorSupplier, that provides access to the FileDescriptor, which in turn contains everything you're looking for.

The slight trick is that the interceptor, with each call, only sees a MethodDescriptor for the method being invoked, which does not appear to have a reference back to its enclosing ServiceDescriptor. So you'd need to construct a "sidecar" map that allows access to the service descriptors from the interceptor(s).

Here's a gist that demonstrates this: https://gist.github.com/jhump/e8f67087ec5a3918f7b270a4a2b83516 (the sidecar map is the MethodOptionsRegistry).

(Word of warning: I have not tried to actually compile and run the gist, so you may find some small errors. But it should at least be instructive in showing everything you actually need.)

----
Josh Humphries
jh...@bluegosling.com

On Tue, Jul 18, 2017 at 1:40 PM, ran.bi via grpc.io <grp...@googlegroups.com> wrote:

What's the best way to get custom method option data (https://developers.google.com/protocol-buffers/docs/proto3#custom_options) from server interceptors?

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