packer-cn/packer/plugin/plugin.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).
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package plugin
import (
"fmt"
"github.com/mitchellh/packer/packer"
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packrpc "github.com/mitchellh/packer/packer/rpc"
"log"
"net"
"net/rpc"
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"os"
"strconv"
"strings"
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)
// This serves a single RPC connection on the given RPC server on
// a random port.
func serve(server *rpc.Server) (err error) {
minPort, err := strconv.ParseInt(os.Getenv("PACKER_PLUGIN_MIN_PORT"), 10, 32)
if err != nil {
return
}
maxPort, err := strconv.ParseInt(os.Getenv("PACKER_PLUGIN_MAX_PORT"), 10, 32)
if err != nil {
return
}
log.Printf("Plugin minimum port: %d\n", minPort)
log.Printf("Plugin maximum port: %d\n", maxPort)
var address string
var listener net.Listener
for port := minPort; port <= maxPort; port++ {
address = fmt.Sprintf(":%d", port)
listener, err = net.Listen("tcp", address)
if err != nil {
if !strings.Contains(err.Error(), "address already in use") {
// Not an address already in use error, return.
return
} else {
// Address is in use, just try another
err = nil
continue
}
}
break
}
defer listener.Close()
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// Output the address to stdout
log.Printf("Plugin address: %s\n", address)
fmt.Println(address)
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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
}
// Serve a single connection
log.Println("Serving a plugin connection...")
server.ServeConn(conn)
return
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}
// Serves a builder from a plugin.
func ServeBuilder(builder packer.Builder) {
log.Println("Preparing to serve a builder plugin...")
server := rpc.NewServer()
packrpc.RegisterBuilder(server, builder)
if err := serve(server); err != nil {
log.Panic(err)
}
}
// Serves a command from a plugin.
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func ServeCommand(command packer.Command) {
log.Println("Preparing to serve a command plugin...")
server := rpc.NewServer()
packrpc.RegisterCommand(server, command)
if err := serve(server); err != nil {
log.Panic(err)
}
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}
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// Serves a hook from a plugin.
func ServeHook(hook packer.Hook) {
log.Println("Preparing to serve a hook plugin...")
server := rpc.NewServer()
packrpc.RegisterHook(server, hook)
if err := serve(server); err != nil {
log.Panic(err)
}
}