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The C based gRPC (C++, Python, Ruby, Objective-C, PHP, C#)
https://grpc.io/
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67 lines
1.9 KiB
67 lines
1.9 KiB
6 years ago
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# Metadata Example
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## Overview
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This example shows you how to add custom headers on the client and server and
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how to access them.
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Custom metadata must follow the "Custom-Metadata" format listed in
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https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md, with the
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exception of binary headers, which don't have to be base64 encoded.
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### Get the tutorial source code
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The example code for this and our other examples lives in the `examples` directory. Clone this repository to your local machine by running the following command:
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```sh
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$ git clone -b $(curl -L https://grpc.io/release) https://github.com/grpc/grpc
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```
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Change your current directory to examples/cpp/metadata
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```sh
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$ cd examples/cpp/metadata
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```
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### Generating gRPC code
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To generate the client and server side interfaces:
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```sh
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$ make helloworld.grpc.pb.cc helloworld.pb.cc
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```
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Which internally invokes the proto-compiler as:
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```sh
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$ protoc -I ../../protos/ --grpc_out=. --plugin=protoc-gen-grpc=grpc_cpp_plugin ../../protos/helloworld.proto
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$ protoc -I ../../protos/ --cpp_out=. ../../protos/helloworld.proto
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```
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### Try it!
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Build client and server:
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```sh
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$ make
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```
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Run the server, which will listen on port 50051:
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```sh
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$ ./greeter_server
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```
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Run the client (in a different terminal):
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```sh
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$ ./greeter_client
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```
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If things go smoothly, you will see in the client terminal:
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"Client received initial metadata from server: initial metadata value"
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"Client received trailing metadata from server: trailing metadata value"
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"Client received message: Hello World"
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And in the server terminal:
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"Header key: custom-bin , value: 01234567"
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"Header key: custom-header , value: Custom Value"
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"Header key: user-agent , value: grpc-c++/1.16.0-dev grpc-c/6.0.0-dev (linux; chttp2; gao)"
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We did not add the user-agent metadata as a custom header. This shows how
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the gRPC framework adds some headers under the hood that may show up in the
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metadata map.
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