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40 lines
2.0 KiB
Markdown
40 lines
2.0 KiB
Markdown
# Concurrency
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In general, gRPC-go provides a concurrency-friendly API. What follows are some
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guidelines.
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## Clients
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A [ClientConn][client-conn] can safely be accessed concurrently. Using
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[helloworld][helloworld] as an example, one could share the `ClientConn` across
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multiple goroutines to create multiple `GreeterClient` types. In this case,
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RPCs would be sent in parallel. `GreeterClient`, generated from the proto
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definitions and wrapping `ClientConn`, is also concurrency safe, and may be
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directly shared in the same way. Note that, as illustrated in
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[the multiplex example][multiplex-example], other `Client` types may share a
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single `ClientConn` as well.
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## Streams
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When using streams, one must take care to avoid calling either `SendMsg` or
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`RecvMsg` multiple times against the same [Stream][stream] from different
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goroutines. In other words, it's safe to have a goroutine calling `SendMsg` and
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another goroutine calling `RecvMsg` on the same stream at the same time. But it
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is not safe to call `SendMsg` on the same stream in different goroutines, or to
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call `RecvMsg` on the same stream in different goroutines.
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## Servers
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Each RPC handler attached to a registered server will be invoked in its own
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goroutine. For example, [SayHello][say-hello] will be invoked in its own
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goroutine. The same is true for service handlers for streaming RPCs, as seen
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in the route guide example [here][route-guide-stream]. Similar to clients,
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multiple services can be registered to the same server.
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[helloworld]: https://github.com/grpc/grpc-go/blob/master/examples/helloworld/greeter_client/main.go#L43
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[client-conn]: https://godoc.org/google.golang.org/grpc#ClientConn
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[stream]: https://godoc.org/google.golang.org/grpc#Stream
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[say-hello]: https://github.com/grpc/grpc-go/blob/master/examples/helloworld/greeter_server/main.go#L41
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[route-guide-stream]: https://github.com/grpc/grpc-go/blob/master/examples/route_guide/server/server.go#L126
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[multiplex-example]: https://github.com/grpc/grpc-go/tree/master/examples/features/multiplex
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