Merge pull request #3105 from philips/add-socket-activation

Add socket activation

systemd/activation/files.go

@@ -0,0 +1,55 @@
+/*
+Copyright 2013 CoreOS Inc.
+
+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 activation implements primitives for systemd socket activation.
+package activation
+
+import (
+	"os"
+	"strconv"
+	"syscall"
+)
+
+// based on: https://gist.github.com/alberts/4640792
+const (
+	listenFdsStart = 3
+)
+
+func Files(unsetEnv bool) []*os.File {
+	if unsetEnv {
+		// there is no way to unset env in golang os package for now
+		// https://code.google.com/p/go/issues/detail?id=6423
+		defer os.Setenv("LISTEN_PID", "")
+		defer os.Setenv("LISTEN_FDS", "")
+	}
+
+	pid, err := strconv.Atoi(os.Getenv("LISTEN_PID"))
+	if err != nil || pid != os.Getpid() {
+		return nil
+	}
+
+	nfds, err := strconv.Atoi(os.Getenv("LISTEN_FDS"))
+	if err != nil || nfds == 0 {
+		return nil
+	}
+
+	var files []*os.File
+	for fd := listenFdsStart; fd < listenFdsStart+nfds; fd++ {
+		syscall.CloseOnExec(fd)
+		files = append(files, os.NewFile(uintptr(fd), "LISTEN_FD_"+strconv.Itoa(fd)))
+	}
+
+	return files
+}

systemd/activation/listeners.go

@@ -0,0 +1,37 @@
+/*
+Copyright 2014 CoreOS Inc.
+
+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 activation
+
+import (
+	"fmt"
+	"net"
+)
+
+// Listeners returns net.Listeners for all socket activated fds passed to this process.
+func Listeners(unsetEnv bool) ([]net.Listener, error) {
+	files := Files(unsetEnv)
+	listeners := make([]net.Listener, len(files))
+
+	for i, f := range files {
+		var err error
+		listeners[i], err = net.FileListener(f)
+		if err != nil {
+			return nil, fmt.Errorf("Error setting up FileListener for fd %d: %s", f.Fd(), err.Error())
+		}
+	}
+
+	return listeners, nil
+}

systemd/listendfd.go

@@ -0,0 +1,40 @@
+package systemd
+
+import (
+	"errors"
+	"net"
+	"strconv"
+
+	"github.com/dotcloud/docker/pkg/systemd/activation"
+)
+
+// ListenFD returns the specified socket activated files as a slice of
+// net.Listeners or all of the activated files if "*" is given.
+func ListenFD(addr string) ([]net.Listener, error) {
+	// socket activation
+	listeners, err := activation.Listeners(false)
+	if err != nil {
+		return nil, err
+	}
+
+	if listeners == nil || len(listeners) == 0 {
+		return nil, errors.New("No sockets found")
+	}
+
+	// default to all fds just like unix:// and tcp://
+	if addr == "" {
+		addr = "*"
+	}
+
+	fdNum, _ := strconv.Atoi(addr)
+	fdOffset := fdNum - 3
+	if (addr != "*") && (len(listeners) < int(fdOffset)+1) {
+		return nil, errors.New("Too few socket activated files passed in")
+	}
+
+	if addr == "*" {
+		return listeners, nil
+	}
+
+	return []net.Listener{listeners[fdOffset]}, nil
+}