// CheckPrereqs will ensure that there are not multiple instances of the
// watchtower running simultaneously. If multiple watchtower containers are
// detected, this function will stop and remove all but the most recently
// started container.
func CheckPrereqs(client container.Client, cleanup bool) error {
containers, err := client.ListContainers(watchtowerContainersFilter)
if err != nil {
return err
}
if len(containers) > 1 {
sort.Sort(container.ByCreated(containers))
// Iterate over all containers execept the last one
for _, c := range containers[0 : len(containers)-1] {
client.StopContainer(c, 60)
if cleanup {
client.RemoveImage(c)
}
}
}
return nil
}
// Update looks at the running Docker containers to see if any of the images
// used to start those containers have been updated. If a change is detected in
// any of the images, the associated containers are stopped and restarted with
// the new image.
func Update(client container.Client, names []string, cleanup bool) error {
log.Info("Checking containers for updated images")
containers, err := client.ListContainers(containerFilter(names))
if err != nil {
return err
}
for i, container := range containers {
stale, err := client.IsContainerStale(container)
if err != nil {
return err
}
containers[i].Stale = stale
}
containers, err = container.SortByDependencies(containers)
if err != nil {
return err
}
checkDependencies(containers)
// Stop stale containers in reverse order
for i := len(containers) - 1; i >= 0; i-- {
container := containers[i]
if container.IsWatchtower() {
continue
}
if container.Stale {
if err := client.StopContainer(container, waitTime); err != nil {
log.Error(err)
}
}
}
// Restart stale containers in sorted order
for _, container := range containers {
if container.Stale {
// Since we can't shutdown a watchtower container immediately, we need to
// start the new one while the old one is still running. This prevents us
// from re-using the same container name so we first rename the current
// instance so that the new one can adopt the old name.
if container.IsWatchtower() {
if err := client.RenameContainer(container, randName()); err != nil {
log.Error(err)
continue
}
}
if err := client.StartContainer(container); err != nil {
log.Error(err)
}
if cleanup {
client.RemoveImage(container)
}
}
}
return nil
}