old vendored code for cn-infra about vpp-agent HOT 6 CLOSED

commit 2e3a708ce83c7ac6a8228a55a8fe2ad1222ed1c9 (HEAD -> master, tag: v1.4.1, origin/master, origin/HEAD)
Merge: f8744581 90d66b84
Author: Ondrej Fabry <[email protected]>
Date:   Mon Jun 11 12:26:26 2018 +0200

    Merge pull request #681 from VladoLavor/release-1.4.1
    
    version 1.4.1 changelog

sbezverk@kube-4:~/developing/go/src/github.com/ligato/vpp-agent$ cat vendor/github.com/ligato/cn-infra/rpc/grpc/listen_and_serve.go
// Copyright (c) 2017 Cisco and/or its affiliates.
//
// 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.

package grpc

import (
        "io"
        "net"
        "time"

        "google.golang.org/grpc"
)

// ListenAndServe is a function that uses <config> & <handler> to handle
// GRPC Requests.
// It return an instance of io.Closer to close the Server (net listener) during cleanup.
type ListenAndServe func(config Config, grpcServer *grpc.Server) (
        netListener io.Closer, err error)

// FromExistingServer is used mainly for testing purposes
func FromExistingServer(listenAndServe ListenAndServe) *Plugin {
        return &Plugin{listenAndServe: listenAndServe}
}

// ListenAndServeGRPC starts a netListener.
func ListenAndServeGRPC(config *Config, grpcServer *grpc.Server) (netListener net.Listener, err error) {
        netListener, err = net.Listen("tcp", config.Endpoint)
        if err != nil {
                return nil, err
        }

        var errCh chan error
        go func() {
                if err := grpcServer.Serve(netListener); err != nil {
                        errCh <- err
                } else {
                        errCh <- nil
                }
        }()

        select {
        case err := <-errCh:
                return nil, err
                // Wait 100ms to create a new stream, so it doesn't bring too much
                // overhead when retry.
        case <-time.After(100 * time.Millisecond):
                //everything is probably fine
                return netListener, nil
        }
}