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69 lines
2.4 KiB
Markdown
69 lines
2.4 KiB
Markdown
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# RPC Errors
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All service method handlers should return `nil` or errors from the
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`status.Status` type. Clients have direct access to the errors.
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Upon encountering an error, a gRPC server method handler should create a
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`status.Status`. In typical usage, one would use [status.New][new-status]
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passing in an appropriate [codes.Code][code] as well as a description of the
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error to produce a `status.Status`. Calling [status.Err][status-err] converts
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the `status.Status` type into an `error`. As a convenience method, there is also
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[status.Error][status-error] which obviates the conversion step. Compare:
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```
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st := status.New(codes.NotFound, "some description")
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err := st.Err()
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// vs.
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err := status.Error(codes.NotFound, "some description")
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```
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## Adding additional details to errors
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In some cases, it may be necessary to add details for a particular error on the
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server side. The [status.WithDetails][with-details] method exists for this
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purpose. Clients may then read those details by first converting the plain
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`error` type back to a [status.Status][status] and then using
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[status.Details][details].
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## Example
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The [example][example] demonstrates the API discussed above and shows how to add
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information about rate limits to the error message using `status.Status`.
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To run the example, first start the server:
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```
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$ go run examples/rpc_errors/server/main.go
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```
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In a separate session, run the client:
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```
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$ go run examples/rpc_errors/client/main.go
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```
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On the first run of the client, all is well:
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```
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2018/03/12 19:39:33 Greeting: Hello world
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```
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Upon running the client a second time, the client exceeds the rate limit and
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receives an error with details:
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```
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2018/03/19 16:42:01 Quota failure: violations:<subject:"name:world" description:"Limit one greeting per person" >
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exit status 1
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```
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[status]: https://godoc.org/google.golang.org/grpc/status#Status
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[new-status]: https://godoc.org/google.golang.org/grpc/status#New
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[code]: https://godoc.org/google.golang.org/grpc/codes#Code
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[with-details]: https://godoc.org/google.golang.org/grpc/status#Status.WithDetails
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[details]: https://godoc.org/google.golang.org/grpc/status#Status.Details
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[status-err]: https://godoc.org/google.golang.org/grpc/status#Status.Err
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[status-error]: https://godoc.org/google.golang.org/grpc/status#Error
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[example]: https://github.com/grpc/grpc-go/tree/master/examples/features/errors
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