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examples: unix abstract socket (#4848)
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# Unix abstract sockets | ||
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This examples shows how to start a gRPC server listening on a unix abstract | ||
socket and how to get a gRPC client to connect to it. | ||
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## What is a unix abstract socket | ||
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An abstract socket address is distinguished from a regular unix socket by the | ||
fact that the first byte of the address is a null byte ('\0'). The address has | ||
no connection with filesystem path names. | ||
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## Try it | ||
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``` | ||
go run server/main.go | ||
``` | ||
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``` | ||
go run client/main.go | ||
``` | ||
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## Explanation | ||
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The gRPC server in this example listens on an address starting with a null byte | ||
and the network is `unix`. The client uses the `unix-abstract` scheme with the | ||
endpoint set to the abstract unix socket address without the null byte. The | ||
`unix` resolver takes care of adding the null byte on the client. See | ||
https://github.com/grpc/grpc/blob/master/doc/naming.md for the more details. | ||
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//go:build linux | ||
// +build linux | ||
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/* | ||
* | ||
* Copyright 2021 gRPC authors. | ||
* | ||
* Licensed under the Apache License, Version 2.0 (the "License"); | ||
* you may not use this file except in compliance with the License. | ||
* You may obtain a copy of the License at | ||
* | ||
* http://www.apache.org/licenses/LICENSE-2.0 | ||
* | ||
* Unless required by applicable law or agreed to in writing, software | ||
* distributed under the License is distributed on an "AS IS" BASIS, | ||
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
* See the License for the specific language governing permissions and | ||
* limitations under the License. | ||
* | ||
*/ | ||
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// Binary client is an example client which dials a server on an abstract unix | ||
// socket. | ||
package main | ||
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import ( | ||
"context" | ||
"fmt" | ||
"log" | ||
"time" | ||
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"google.golang.org/grpc" | ||
ecpb "google.golang.org/grpc/examples/features/proto/echo" | ||
) | ||
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func callUnaryEcho(c ecpb.EchoClient, message string) { | ||
ctx, cancel := context.WithTimeout(context.Background(), time.Second) | ||
defer cancel() | ||
r, err := c.UnaryEcho(ctx, &ecpb.EchoRequest{Message: message}) | ||
if err != nil { | ||
log.Fatalf("could not greet: %v", err) | ||
} | ||
fmt.Println(r.Message) | ||
} | ||
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func makeRPCs(cc *grpc.ClientConn, n int) { | ||
hwc := ecpb.NewEchoClient(cc) | ||
for i := 0; i < n; i++ { | ||
callUnaryEcho(hwc, "this is examples/unix_abstract") | ||
} | ||
} | ||
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func main() { | ||
// A dial target of `unix:@abstract-unix-socket` should also work fine for | ||
// this example because of golang conventions (net.Dial behavior). But we do | ||
// not recommend this since we explicitly added the `unix-abstract` scheme | ||
// for cross-language compatibility. | ||
addr := "unix-abstract:abstract-unix-socket" | ||
cc, err := grpc.Dial(addr, grpc.WithInsecure(), grpc.WithBlock()) | ||
if err != nil { | ||
log.Fatalf("grpc.Dial(%q) failed: %v", addr, err) | ||
} | ||
defer cc.Close() | ||
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fmt.Printf("--- calling echo.Echo/UnaryEcho to %s\n", addr) | ||
makeRPCs(cc, 10) | ||
fmt.Println() | ||
} |
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//go:build linux | ||
// +build linux | ||
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/* | ||
* | ||
* Copyright 2021 gRPC authors. | ||
* | ||
* Licensed under the Apache License, Version 2.0 (the "License"); | ||
* you may not use this file except in compliance with the License. | ||
* You may obtain a copy of the License at | ||
* | ||
* http://www.apache.org/licenses/LICENSE-2.0 | ||
* | ||
* Unless required by applicable law or agreed to in writing, software | ||
* distributed under the License is distributed on an "AS IS" BASIS, | ||
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
* See the License for the specific language governing permissions and | ||
* limitations under the License. | ||
* | ||
*/ | ||
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// Binary server is an example server listening for gRPC connections on an | ||
// abstract unix socket. | ||
package main | ||
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import ( | ||
"context" | ||
"fmt" | ||
"log" | ||
"net" | ||
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"google.golang.org/grpc" | ||
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pb "google.golang.org/grpc/examples/features/proto/echo" | ||
) | ||
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type ecServer struct { | ||
pb.UnimplementedEchoServer | ||
addr string | ||
} | ||
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func (s *ecServer) UnaryEcho(ctx context.Context, req *pb.EchoRequest) (*pb.EchoResponse, error) { | ||
return &pb.EchoResponse{Message: fmt.Sprintf("%s (from %s)", req.Message, s.addr)}, nil | ||
} | ||
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func main() { | ||
netw, addr := "unix", "\x00abstract-unix-socket" | ||
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lis, err := net.Listen(netw, addr) | ||
if err != nil { | ||
log.Fatalf("net.Listen(%q, %q) failed: %v", netw, addr, err) | ||
} | ||
s := grpc.NewServer() | ||
pb.RegisterEchoServer(s, &ecServer{addr: addr}) | ||
log.Printf("serving on %s\n", lis.Addr().String()) | ||
if err := s.Serve(lis); err != nil { | ||
log.Fatalf("failed to serve: %v", err) | ||
} | ||
} |
You can also use
@
instead of\x00
to listen on an abstract socket, eg."@abstract-unix-socket"
. This is a common convention for how abstract sockets are displayed. And the Go stdlib will convert a unix address that starts with@
to one that starts with a 0-byte. https://github.com/golang/go/blob/go1.17/src/syscall/syscall_linux.go#L429