Documentation
¶
Overview ¶
Package proxy provides a reverse proxy handler for gRPC.
The implementation allows a `grpc.Server` to pass a received ServerStream to a ClientStream without understanding the semantics of the messages exchanged. It basically provides a transparent reverse-proxy.
This package is intentionally generic, exposing a `StreamDirector` function that allows users of this package to implement whatever logic of backend-picking, dialing and service verification to perform.
See examples on documented functions.
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func Codec ¶
Codec returns a proxying grpc.Codec with the default protobuf codec as parent.
See CodecWithParent.
func CodecWithParent ¶
CodecWithParent returns a proxying grpc.Codec with a user provided codec as parent.
This codec is *crucial* to the functioning of the proxy. It allows the proxy server to be oblivious to the schema of the forwarded messages. It basically treats a gRPC message frame as raw bytes. However, if the server handler, or the client caller are not proxy-internal functions it will fall back to trying to decode the message using a fallback codec.
func RegisterService ¶
func RegisterService(server *grpc.Server, director StreamDirector, serviceName string, methodNames ...string)
RegisterService sets up a proxy handler for a particular gRPC service and method. The behaviour is the same as if you were registering a handler method, e.g. from a codegenerated pb.go file.
This can *only* be used if the `server` also uses grpcproxy.CodecForServer() ServerOption.
Example ¶
package main
import (
proxy "github.com/alexshvid/grpc-proxy"
"google.golang.org/grpc"
)
var director proxy.StreamDirector
func main() {
// A gRPC server with the proxying codec enabled.
server := grpc.NewServer(grpc.CustomCodec(proxy.Codec()))
// Register a TestService with 4 of its methods explicitly.
proxy.RegisterService(server, director,
"mwitkow.testproto.TestService",
"PingEmpty", "Ping", "PingError", "PingList")
}
Output:
func TransparentHandler ¶
func TransparentHandler(director StreamDirector) grpc.StreamHandler
TransparentHandler returns a handler that attempts to proxy all requests that are not registered in the server. The indented use here is as a transparent proxy, where the server doesn't know about the services implemented by the backends. It should be used as a `grpc.UnknownServiceHandler`.
This can *only* be used if the `server` also uses grpcproxy.CodecForServer() ServerOption.
Example ¶
package main
import (
proxy "github.com/alexshvid/grpc-proxy"
"google.golang.org/grpc"
)
var director proxy.StreamDirector
func main() {
grpc.NewServer(
grpc.CustomCodec(proxy.Codec()),
grpc.UnknownServiceHandler(proxy.TransparentHandler(director)))
}
Output:
Types ¶
type StreamDirector ¶
type StreamDirector func(ctx context.Context, fullMethodName string) (context.Context, *grpc.ClientConn, error)
StreamDirector returns a gRPC ClientConn to be used to forward the call to.
The presence of the `Context` allows for rich filtering, e.g. based on Metadata (headers). If no handling is meant to be done, a `codes.NotImplemented` gRPC error should be returned.
The context returned from this function should be the context for the *outgoing* (to backend) call. In case you want to forward any Metadata between the inbound request and outbound requests, you should do it manually. However, you *must* propagate the cancel function (`context.WithCancel`) of the inbound context to the one returned.
It is worth noting that the StreamDirector will be fired *after* all server-side stream interceptors are invoked. So decisions around authorization, monitoring etc. are better to be handled there.
See the rather rich example.
Example ¶
Provide sa simple example of a director that shields internal services and dials a staging or production backend. This is a *very naive* implementation that creates a new connection on every request. Consider using pooling.
package main
import (
"strings"
proxy "github.com/alexshvid/grpc-proxy"
"golang.org/x/net/context"
"google.golang.org/grpc"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/metadata"
)
var director proxy.StreamDirector
func main() {
director = func(ctx context.Context, fullMethodName string) (context.Context, *grpc.ClientConn, error) {
// Make sure we never forward internal services.
if strings.HasPrefix(fullMethodName, "/com.example.internal.") {
return nil, nil, grpc.Errorf(codes.Unimplemented, "Unknown method")
}
md, ok := metadata.FromIncomingContext(ctx)
// Copy the inbound metadata explicitly.
outCtx, _ := context.WithCancel(ctx)
outCtx = metadata.NewOutgoingContext(outCtx, md.Copy())
if ok {
// Decide on which backend to dial
if val, exists := md[":authority"]; exists && val[0] == "staging.api.example.com" {
// Make sure we use DialContext so the dialing can be cancelled/time out together with the context.
conn, err := grpc.DialContext(ctx, "api-service.staging.svc.local", grpc.WithCodec(proxy.Codec()))
return outCtx, conn, err
} else if val, exists := md[":authority"]; exists && val[0] == "api.example.com" {
conn, err := grpc.DialContext(ctx, "api-service.prod.svc.local", grpc.WithCodec(proxy.Codec()))
return outCtx, conn, err
}
}
return nil, nil, grpc.Errorf(codes.Unimplemented, "Unknown method")
}
}
Output:
Source Files
Directories
¶
| Path | Synopsis |
|---|---|
|
Package mwitkow_testproto is a generated protocol buffer package.
|
Package mwitkow_testproto is a generated protocol buffer package. |