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81 lines
3.5 KiB
Markdown
81 lines
3.5 KiB
Markdown
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# Compression
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The preferred method for configuring message compression on both clients and
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servers is to use
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[`encoding.RegisterCompressor`](https://godoc.org/google.golang.org/grpc/encoding#RegisterCompressor)
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to register an implementation of a compression algorithm. See
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`grpc/encoding/gzip/gzip.go` for an example of how to implement one.
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Once a compressor has been registered on the client-side, RPCs may be sent using
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it via the
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[`UseCompressor`](https://godoc.org/google.golang.org/grpc#UseCompressor)
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`CallOption`. Remember that `CallOption`s may be turned into defaults for all
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calls from a `ClientConn` by using the
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[`WithDefaultCallOptions`](https://godoc.org/google.golang.org/grpc#WithDefaultCallOptions)
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`DialOption`. If `UseCompressor` is used and the corresponding compressor has
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not been installed, an `Internal` error will be returned to the application
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before the RPC is sent.
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Server-side, registered compressors will be used automatically to decode request
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messages and encode the responses. Servers currently always respond using the
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same compression method specified by the client. If the corresponding
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compressor has not been registered, an `Unimplemented` status will be returned
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to the client.
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## Deprecated API
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There is a deprecated API for setting compression as well. It is not
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recommended for use. However, if you were previously using it, the following
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section may be helpful in understanding how it works in combination with the new
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API.
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### Client-Side
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There are two legacy functions and one new function to configure compression:
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```go
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func WithCompressor(grpc.Compressor) DialOption {}
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func WithDecompressor(grpc.Decompressor) DialOption {}
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func UseCompressor(name) CallOption {}
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```
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For outgoing requests, the following rules are applied in order:
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1. If `UseCompressor` is used, messages will be compressed using the compressor
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named.
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* If the compressor named is not registered, an Internal error is returned
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back to the client before sending the RPC.
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* If UseCompressor("identity"), no compressor will be used, but "identity"
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will be sent in the header to the server.
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1. If `WithCompressor` is used, messages will be compressed using that
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compressor implementation.
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1. Otherwise, outbound messages will be uncompressed.
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For incoming responses, the following rules are applied in order:
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1. If `WithDecompressor` is used and it matches the message's encoding, it will
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be used.
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1. If a registered compressor matches the response's encoding, it will be used.
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1. Otherwise, the stream will be closed and an `Unimplemented` status error will
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be returned to the application.
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### Server-Side
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There are two legacy functions to configure compression:
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```go
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func RPCCompressor(grpc.Compressor) ServerOption {}
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func RPCDecompressor(grpc.Decompressor) ServerOption {}
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```
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For incoming requests, the following rules are applied in order:
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1. If `RPCDecompressor` is used and that decompressor matches the request's
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encoding: it will be used.
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1. If a registered compressor matches the request's encoding, it will be used.
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1. Otherwise, an `Unimplemented` status will be returned to the client.
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For outgoing responses, the following rules are applied in order:
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1. If `RPCCompressor` is used, that compressor will be used to compress all
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response messages.
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1. If compression was used for the incoming request and a registered compressor
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supports it, that same compression method will be used for the outgoing
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response.
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1. Otherwise, no compression will be used for the outgoing response.
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