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main.go
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/
main.go
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// Copyright Lorenz Leutgeb <lorenz@leutgeb.xyz>
//
// 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.
// +build darwin dragonfly freebsd linux netbsd openbsd solaris
package main
import (
"bufio"
"errors"
"fmt"
"io"
"io/ioutil"
"log"
"os"
"os/exec"
"path/filepath"
"strings"
"sync"
"github.com/docker/go-plugins-helpers/volume"
)
// Socket address by convention. Docker will look there, so
// this needs to be in sync with upstream.
const socketAddress = "/run/docker/plugins/gcs.sock"
var (
errDaemonDirty = errors.New("gcsfuse did not exit cleanly")
errUnknownVolume = errors.New("unknwon volume, no gcfsfuse instance found")
errZombie = errors.New("found gcfsfuse instance where there should be none")
)
type errBadRead struct {
cause error
}
func (e errBadRead) Error() string {
return fmt.Sprintf("failed to read from gcfsfuse, caused by: %s", e.cause.Error())
}
type errUnexpectedOutput struct {
output string
}
func (e errUnexpectedOutput) Error() string {
return fmt.Sprintf("unexpected output from gcfsfuse: %s", e.output)
}
// driver wraps multiple gcsfuse processes
type driver struct {
*sync.Mutex
// Maps bucket to the gcfsfuse command that owns the bucket.
cmds map[string]exec.Cmd
}
var root = os.Args[len(os.Args)-1]
func init() {
if _, err := exec.LookPath("gcsfuse"); err != nil {
log.Fatal("Could not find gcsfuse.")
}
log.SetFlags(log.Lmicroseconds)
}
func main() {
d := driver{
Mutex: new(sync.Mutex),
cmds: make(map[string]exec.Cmd),
}
h := volume.NewHandler(d)
log.Printf("Listening on %s with mount target %s\n", socketAddress, root)
log.Println(h.ServeUnix(socketAddress, 0))
}
func (d driver) Mount(r *volume.MountRequest) (*volume.MountResponse, error) {
d.Lock()
defer d.Unlock()
b := d.bucket(r.Name)
daemon, ok := d.cmds[b]
if ok {
if daemon.ProcessState != nil && daemon.ProcessState.Exited() {
return nil, errZombie
}
return &volume.MountResponse{Mountpoint: d.mountpoint(r.Name)}, nil
}
mnt := d.mountpoint(b)
if err := os.MkdirAll(mnt, os.ModeTemporary); err != nil {
return nil, err
}
daemon = *exec.Command("gcsfuse", append(os.Args[1:len(os.Args)-1], b, mnt)...)
daemon.Stdout = os.Stdout
rc, err := daemon.StderrPipe()
if err != nil {
return nil, errBadRead{err}
}
if err := daemon.Start(); err != nil {
return nil, err
}
l, err := bufio.NewReader(io.TeeReader(rc, os.Stderr)).ReadString(byte('\n'))
if err != nil {
return nil, errBadRead{err}
}
if !strings.HasSuffix(l, "File system has been successfully mounted.\n") {
return nil, errUnexpectedOutput{output: l}
}
d.cmds[b] = daemon
go io.Copy(os.Stderr, rc)
return &volume.MountResponse{Mountpoint: d.mountpoint(r.Name)}, nil
}
func (d driver) Remove(r *volume.RemoveRequest) error {
d.Lock()
defer d.Unlock()
b := d.bucket(r.Name)
daemon, ok := d.cmds[b]
if !ok {
log.Printf("Doing nothing when asked to remove volume for %s ...", r.Name)
return nil
}
log.Printf("Interrupting gcsfuse %s", b)
daemon.Process.Signal(os.Interrupt)
ps, err := daemon.Process.Wait()
if err != nil {
log.Printf("Waiting for gcsfuse %s errored, returning error.", b)
return err
}
if !ps.Success() {
log.Printf("gcsfuse %s exited dirty, returning error.", b)
return errDaemonDirty
}
return nil
}
func (d driver) Get(r *volume.GetRequest) (*volume.GetResponse, error) {
d.Lock()
defer d.Unlock()
return &volume.GetResponse{
Volume: &volume.Volume{
Name: r.Name,
Mountpoint: d.mountpoint(r.Name),
},
}, nil
}
func (d driver) List() (*volume.ListResponse, error) {
d.Lock()
defer d.Unlock()
var volumes []*volume.Volume
files, err := ioutil.ReadDir(root)
if err != nil {
return nil, err
}
for _, entry := range files {
if entry.IsDir() {
volumes = append(volumes, &volume.Volume{Name: entry.Name(), Mountpoint: d.mountpoint(entry.Name())})
}
}
return &volume.ListResponse{Volumes: volumes}, nil
}
func (d driver) Path(r *volume.PathRequest) (*volume.PathResponse, error) {
return &volume.PathResponse{Mountpoint: d.mountpoint(r.Name)}, nil
}
func (d driver) Create(r *volume.CreateRequest) error {
return nil
}
func (d driver) Unmount(r *volume.UnmountRequest) error {
return nil
}
func (d driver) mountpoint(name string) string {
return filepath.Join(root, name)
}
func (d driver) bucket(name string) string {
i := strings.Index(name, "/")
if i == -1 {
return name
}
return name[0:i]
}
func (d driver) Capabilities() *volume.CapabilitiesResponse {
return &volume.CapabilitiesResponse{
Capabilities: volume.Capability{Scope: "global"},
}
}