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Cleanup: refactor shutdown and signal handling facility

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This disentangles the following functions, which were previously all mixed together:

* 1) Waiting for jobs to terminate when shutting down
* 2) Handling signals in the Docker daemon
* 3) Per-subsystem cleanup handlers
* 4) pidfile management

Responsibilities are dispatched as follows:

* Signal traps are set in `main`, and trigger `engine.Shutdown`
* `engine.Shutdown` coordinates cleanup by waiting for jobs to complete, and calling shutdown handlers
* To perform cleanup at shutdown, each subsystem registers handlers with `engine.OnShutdown`
* `daemon` is one subsystem, so it registers cleanup via `engine.OnShutdown`.
* `daemon` owns the pidfile, which is used to lock access to `/var/lib/docker`. Part of its cleanup is to remove the pidfile.

Signed-off-by: Solomon Hykes <solomon@docker.com>
This commit is contained in:
Solomon Hykes
2014-08-06 17:56:11 +00:00
parent d55e3fea72
commit c9f3fd3fc7
4 changed files with 40 additions and 55 deletions
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daemon/daemon.go
+36 -26
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@@ -667,6 +667,20 @@ func NewDaemon(config *daemonconfig.Config, eng *engine.Engine) (*Daemon, error)
}
func NewDaemonFromDirectory(config *daemonconfig.Config, eng *engine.Engine) (*Daemon, error) {
// Claim the pidfile first, to avoid any and all unexpected race conditions.
// Some of the init doesn't need a pidfile lock - but let's not try to be smart.
if config.Pidfile != "" {
if err := utils.CreatePidFile(config.Pidfile); err != nil {
return nil, err
}
eng.OnShutdown(func() {
// Always release the pidfile last, just in case
utils.RemovePidFile(config.Pidfile)
})
}
// Check that the system is supported and we have sufficient privileges
// FIXME: return errors instead of calling Fatal
if runtime.GOOS != "linux" {
log.Fatalf("The Docker daemon is only supported on linux")
}
@@ -819,13 +833,32 @@ func NewDaemonFromDirectory(config *daemonconfig.Config, eng *engine.Engine) (*D
eng: eng,
Sockets: config.Sockets,
}
if err := daemon.checkLocaldns(); err != nil {
return nil, err
}
if err := daemon.restore(); err != nil {
return nil, err
}
// Setup shutdown handlers
// FIXME: can these shutdown handlers be registered closer to their source?
eng.OnShutdown(func() {
// FIXME: if these cleanup steps can be called concurrently, register
// them as separate handlers to speed up total shutdown time
// FIXME: use engine logging instead of utils.Errorf
if err := daemon.shutdown(); err != nil {
utils.Errorf("daemon.shutdown(): %s", err)
}
if err := portallocator.ReleaseAll(); err != nil {
utils.Errorf("portallocator.ReleaseAll(): %s", err)
}
if err := daemon.driver.Cleanup(); err != nil {
utils.Errorf("daemon.driver.Cleanup(): %s", err.Error())
}
if err := daemon.containerGraph.Close(); err != nil {
utils.Errorf("daemon.containerGraph.Close(): %s", err.Error())
}
})
return daemon, nil
}
@@ -853,30 +886,6 @@ func (daemon *Daemon) shutdown() error {
return nil
}
func (daemon *Daemon) Close() error {
errorsStrings := []string{}
if err := daemon.shutdown(); err != nil {
utils.Errorf("daemon.shutdown(): %s", err)
errorsStrings = append(errorsStrings, err.Error())
}
if err := portallocator.ReleaseAll(); err != nil {
utils.Errorf("portallocator.ReleaseAll(): %s", err)
errorsStrings = append(errorsStrings, err.Error())
}
if err := daemon.driver.Cleanup(); err != nil {
utils.Errorf("daemon.driver.Cleanup(): %s", err.Error())
errorsStrings = append(errorsStrings, err.Error())
}
if err := daemon.containerGraph.Close(); err != nil {
utils.Errorf("daemon.containerGraph.Close(): %s", err.Error())
errorsStrings = append(errorsStrings, err.Error())
}
if len(errorsStrings) > 0 {
return fmt.Errorf("%s", strings.Join(errorsStrings, ", "))
}
return nil
}
func (daemon *Daemon) Mount(container *Container) error {
dir, err := daemon.driver.Get(container.ID, container.GetMountLabel())
if err != nil {
@@ -967,6 +976,8 @@ func (daemon *Daemon) Kill(c *Container, sig int) error {
// from the content root, including images, volumes and
// container filesystems.
// Again: this will remove your entire docker daemon!
// FIXME: this is deprecated, and only used in legacy
// tests. Please remove.
func (daemon *Daemon) Nuke() error {
var wg sync.WaitGroup
for _, container := range daemon.List() {
@@ -977,7 +988,6 @@ func (daemon *Daemon) Nuke() error {
}(container)
}
wg.Wait()
daemon.Close()
return os.RemoveAll(daemon.config.Root)
}