vendor files

vendor/google.golang.org/grpc/Documentation/compression.md

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