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59 lines
2.6 KiB
Markdown
59 lines
2.6 KiB
Markdown
# Stats Monitoring Handler
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This example demonstrates the use of the [`stats`](https://pkg.go.dev/google.golang.org/grpc/stats) package for reporting various
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network and RPC stats.
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_Note that all fields are READ-ONLY and the APIs of the `stats` package are
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experimental_.
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## Try it
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```
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go run server/main.go
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```
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```
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go run client/main.go
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```
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## Explanation
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gRPC provides a mechanism to hook on to various events (phases) of the
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request-response network cycle through the [`stats.Handler`](https://pkg.go.dev/google.golang.org/grpc/stats#Handler) interface. To access
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these events, a concrete type that implements `stats.Handler` should be passed to
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`grpc.WithStatsHandler()` on the client side and `grpc.StatsHandler()` on the
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server side.
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The `HandleRPC(context.Context, RPCStats)` method on `stats.Handler` is called
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multiple times during a request-response cycle, and various event stats are
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passed to its `RPCStats` parameter (an interface). The concrete types that
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implement this interface are: `*stats.Begin`, `*stats.InHeader`, `*stats.InPayload`,
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`*stats.InTrailer`, `*stats.OutHeader`, `*stats.OutPayload`, `*stats.OutTrailer`, and
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`*stats.End`. The order of these events differs on client and server.
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Similarly, the `HandleConn(context.Context, ConnStats)` method on `stats.Handler`
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is called twice, once at the beginning of the connection with `*stats.ConnBegin`
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and once at the end with `*stats.ConnEnd`.
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The [`stats.Handler`](https://pkg.go.dev/google.golang.org/grpc/stats#Handler) interface also provides
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`TagRPC(context.Context, *RPCTagInfo) context.Context` and
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`TagConn(context.Context, *ConnTagInfo) context.Context` methods. These methods
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are mainly used to attach network related information to the given context.
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The `TagRPC(context.Context, *RPCTagInfo) context.Context` method returns a
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context from which the context used for the rest lifetime of the RPC will be
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derived. This behavior is consistent between the gRPC client and server.
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The context returned from
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`TagConn(context.Context, *ConnTagInfo) context.Context` has varied lifespan:
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- In the gRPC client:
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The context used for the rest lifetime of the RPC will NOT be derived from
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this context. Hence the information attached to this context can only be
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consumed by `HandleConn(context.Context, ConnStats)` method.
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- In the gRPC server:
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The context used for the rest lifetime of the RPC will be derived from
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this context.
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NOTE: The [stats](https://pkg.go.dev/google.golang.org/grpc/stats) package should only be used for network monitoring purposes,
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and not as an alternative to [interceptors](https://github.com/grpc/grpc-go/blob/master/examples/features/interceptor).
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