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server.go
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server.go
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// The plugin package provides the functionality to both expose a Packer
// plugin binary and to connect to an existing Packer plugin binary.
//
// Packer supports plugins in the form of self-contained external static
// Go binaries. These binaries behave in a certain way (enforced by this
// package) and are connected to in a certain way (also enforced by this
// package).
package plugin
import (
"errors"
"fmt"
"github.com/mitchellh/packer/packer"
packrpc "github.com/mitchellh/packer/packer/rpc"
"io/ioutil"
"log"
"net"
"os"
"os/signal"
"runtime"
"strconv"
"sync/atomic"
)
// This is a count of the number of interrupts the process has received.
// This is updated with sync/atomic whenever a SIGINT is received and can
// be checked by the plugin safely to take action.
var Interrupts int32 = 0
const MagicCookieKey = "PACKER_PLUGIN_MAGIC_COOKIE"
const MagicCookieValue = "d602bf8f470bc67ca7faa0386276bbdd4330efaf76d1a219cb4d6991ca9872b2"
// The APIVersion is outputted along with the RPC address. The plugin
// client validates this API version and will show an error if it doesn't
// know how to speak it.
const APIVersion = "2"
// Server waits for a connection to this plugin and returns a Packer
// RPC server that you can use to register components and serve them.
func Server() (*packrpc.Server, error) {
log.Printf("Plugin build against Packer '%s'", packer.GitCommit)
if os.Getenv(MagicCookieKey) != MagicCookieValue {
return nil, errors.New(
"Please do not execute plugins directly. Packer will execute these for you.")
}
// If there is no explicit number of Go threads to use, then set it
if os.Getenv("GOMAXPROCS") == "" {
runtime.GOMAXPROCS(runtime.NumCPU())
}
minPort, err := strconv.ParseInt(os.Getenv("PACKER_PLUGIN_MIN_PORT"), 10, 32)
if err != nil {
return nil, err
}
maxPort, err := strconv.ParseInt(os.Getenv("PACKER_PLUGIN_MAX_PORT"), 10, 32)
if err != nil {
return nil, err
}
log.Printf("Plugin minimum port: %d\n", minPort)
log.Printf("Plugin maximum port: %d\n", maxPort)
listener, err := serverListener(minPort, maxPort)
if err != nil {
return nil, err
}
defer listener.Close()
// Output the address to stdout
log.Printf("Plugin address: %s %s\n",
listener.Addr().Network(), listener.Addr().String())
fmt.Printf("%s|%s|%s\n",
APIVersion,
listener.Addr().Network(),
listener.Addr().String())
os.Stdout.Sync()
// Accept a connection
log.Println("Waiting for connection...")
conn, err := listener.Accept()
if err != nil {
log.Printf("Error accepting connection: %s\n", err.Error())
return nil, err
}
// Eat the interrupts
ch := make(chan os.Signal, 1)
signal.Notify(ch, os.Interrupt)
go func() {
var count int32 = 0
for {
<-ch
newCount := atomic.AddInt32(&count, 1)
log.Printf("Received interrupt signal (count: %d). Ignoring.", newCount)
}
}()
// Serve a single connection
log.Println("Serving a plugin connection...")
return packrpc.NewServer(conn), nil
}
func serverListener(minPort, maxPort int64) (net.Listener, error) {
if runtime.GOOS == "windows" {
return serverListener_tcp(minPort, maxPort)
}
return serverListener_unix()
}
func serverListener_tcp(minPort, maxPort int64) (net.Listener, error) {
for port := minPort; port <= maxPort; port++ {
address := fmt.Sprintf("127.0.0.1:%d", port)
listener, err := net.Listen("tcp", address)
if err == nil {
return listener, nil
}
}
return nil, errors.New("Couldn't bind plugin TCP listener")
}
func serverListener_unix() (net.Listener, error) {
tf, err := ioutil.TempFile("", "packer-plugin")
if err != nil {
return nil, err
}
path := tf.Name()
// Close the file and remove it because it has to not exist for
// the domain socket.
if err := tf.Close(); err != nil {
return nil, err
}
if err := os.Remove(path); err != nil {
return nil, err
}
return net.Listen("unix", path)
}