// upgradeCharm upgrades the charm for the given service to the given charm id.
// If the service is already deployed using the given charm id, do nothing.
// This function returns an error if the existing charm and the target one are
// incompatible, meaning an upgrade from one to the other is not allowed.
func upgradeCharm(client *api.Client, log deploymentLogger, service, id string) error {
existing, err := client.ServiceGetCharmURL(service)
if err != nil {
return errors.Annotatef(err, "cannot retrieve info for service %q", service)
}
if existing.String() == id {
log.Infof("reusing service %s (charm: %s)", service, id)
return nil
}
url, err := charm.ParseURL(id)
if err != nil {
return errors.Annotatef(err, "cannot parse charm URL %q", id)
}
if url.WithRevision(-1).Path() != existing.WithRevision(-1).Path() {
return errors.Errorf("bundle charm %q is incompatible with existing charm %q", id, existing)
}
if err := client.ServiceSetCharm(service, id, false); err != nil {
return errors.Annotatef(err, "cannot upgrade charm to %q", id)
}
log.Infof("upgraded charm for existing service %s (from %s to %s)", service, existing, id)
return nil
}