mirror of https://github.com/grpc/grpc.git
The C based gRPC (C++, Python, Ruby, Objective-C, PHP, C#)
https://grpc.io/
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
66 lines
1.9 KiB
66 lines
1.9 KiB
# Metadata Example |
|
|
|
## Overview |
|
|
|
This example shows you how to add custom headers on the client and server and |
|
how to access them. |
|
|
|
Custom metadata must follow the "Custom-Metadata" format listed in |
|
https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md, with the |
|
exception of binary headers, which don't have to be base64 encoded. |
|
|
|
### Get the tutorial source code |
|
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: |
|
```sh |
|
$ git clone -b $(curl -L https://grpc.io/release) https://github.com/grpc/grpc |
|
``` |
|
Change your current directory to examples/cpp/metadata |
|
```sh |
|
$ cd examples/cpp/metadata |
|
``` |
|
|
|
### Generating gRPC code |
|
To generate the client and server side interfaces: |
|
```sh |
|
$ make helloworld.grpc.pb.cc helloworld.pb.cc |
|
``` |
|
Which internally invokes the proto-compiler as: |
|
```sh |
|
$ protoc -I ../../protos/ --grpc_out=. --plugin=protoc-gen-grpc=grpc_cpp_plugin ../../protos/helloworld.proto |
|
$ protoc -I ../../protos/ --cpp_out=. ../../protos/helloworld.proto |
|
``` |
|
### Try it! |
|
Build client and server: |
|
|
|
```sh |
|
$ make |
|
``` |
|
|
|
Run the server, which will listen on port 50051: |
|
|
|
```sh |
|
$ ./greeter_server |
|
``` |
|
|
|
Run the client (in a different terminal): |
|
|
|
```sh |
|
$ ./greeter_client |
|
``` |
|
|
|
If things go smoothly, you will see in the client terminal: |
|
|
|
"Client received initial metadata from server: initial metadata value" |
|
"Client received trailing metadata from server: trailing metadata value" |
|
"Client received message: Hello World" |
|
|
|
|
|
And in the server terminal: |
|
|
|
"Header key: custom-bin , value: 01234567" |
|
"Header key: custom-header , value: Custom Value" |
|
"Header key: user-agent , value: grpc-c++/1.16.0-dev grpc-c/6.0.0-dev (linux; chttp2; gao)" |
|
|
|
We did not add the user-agent metadata as a custom header. This shows how |
|
the gRPC framework adds some headers under the hood that may show up in the |
|
metadata map.
|
|
|