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70 lines
1.7 KiB
70 lines
1.7 KiB
6 months ago
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# Retry
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This example shows how to enable and configure retry on gRPC clients.
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## Documentation
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[gRFC for client-side retry support](https://github.com/grpc/proposal/blob/master/A6-client-retries.md)
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## Try it
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This example includes a service implementation that fails requests three times with status
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code `Unavailable`, then passes the fourth. The client is configured to make four retry attempts
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when receiving an `Unavailable` status code.
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First start the server:
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```bash
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$ ./server
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```
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Then run the client:
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```bash
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$ ./client
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```
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Expected server output:
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```
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Server listening on 0.0.0.0:50052
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return UNAVAILABLE
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return UNAVAILABLE
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return UNAVAILABLE
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return OK
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```
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Expected client output:
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```
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Greeter received: Hello world
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```
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## Usage
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### Define your retry policy
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Retry is enabled via the service config, which can be provided by the name resolver or
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a [GRPC_ARG_SERVICE_CONFIG](https://github.com/grpc/grpc/blob/master/include/grpc/impl/channel_arg_names.h#L207-L209) channel argument. In the below config, we set retry policy for the "helloworld.Greeter" service.
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`maxAttempts`: how many times to attempt the RPC before failing.
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`initialBackoff`, `maxBackoff`, `backoffMultiplier`: configures delay between attempts.
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`retryableStatusCodes`: Retry only when receiving these status codes.
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```c++
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constexpr absl::string_view kRetryPolicy =
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"{\"methodConfig\" : [{"
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" \"name\" : [{\"service\": \"helloworld.Greeter\"}],"
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" \"waitForReady\": true,"
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" \"retryPolicy\": {"
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" \"maxAttempts\": 4,"
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" \"initialBackoff\": \"1s\","
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" \"maxBackoff\": \"120s\","
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" \"backoffMultiplier\": 1.0,"
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" \"retryableStatusCodes\": [\"UNAVAILABLE\"]"
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" }"
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"}]}";
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```
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