func (b *etcdBackend) SetServiceMeta(service string, meta *discoverd.ServiceMeta) error {
serviceKey := b.serviceKey(service)
_, err := b.etcd.Get(serviceKey, false, false)
if isEtcdNotFound(err) {
return NotFoundError{Service: service}
}
if err != nil {
return err
}
var res *etcd.Response
key := path.Join(serviceKey, "meta")
if meta.Index == 0 {
res, err = b.etcd.Create(key, string(meta.Data), 0)
if isEtcdExists(err) {
err = hh.ObjectExistsErr(fmt.Sprintf("Service metadata for %q already exists, use index=n to set", service))
}
} else {
res, err = b.etcd.CompareAndSwap(key, string(meta.Data), 0, "", meta.Index)
if isEtcdNotFound(err) {
err = hh.PreconditionFailedErr(fmt.Sprintf("Service metadata for %q does not exist, use index=0 to set", service))
} else if isEtcdCompareFailed(err) {
err = hh.PreconditionFailedErr(fmt.Sprintf("Service metadata for %q exists, but wrong index provided", service))
}
}
if err != nil {
return err
}
meta.Index = res.Node.ModifiedIndex
return nil
}
func (s *Store) applySetServiceMetaCommand(cmd []byte, index uint64) error {
var c setServiceMetaCommand
if err := json.Unmarshal(cmd, &c); err != nil {
return err
}
// Verify that the service exists.
service := s.data.Services[c.Service]
if service == nil {
return NotFoundError{Service: c.Service}
}
// If no index is provided then the meta should not be set.
curr := s.data.Metas[c.Service]
if c.Meta.Index == 0 {
if curr != nil {
return hh.ObjectExistsErr(fmt.Sprintf("Service metadata for %q already exists, use index=n to set", c.Service))
}
} else {
if curr == nil {
return hh.PreconditionFailedErr(fmt.Sprintf("Service metadata for %q does not exist, use index=0 to set", c.Service))
} else if curr.Index != c.Meta.Index {
return hh.PreconditionFailedErr(fmt.Sprintf("Service metadata for %q exists, but wrong index provided", c.Service))
}
}
leaderID := c.Meta.LeaderID
c.Meta.LeaderID = ""
// Update the meta and set the index.
c.Meta.Index = index
s.data.Metas[c.Service] = c.Meta
if leaderID != "" {
// If a new leader was included in the meta update, apply it
s.data.Leaders[c.Service] = leaderID
}
// Broadcast EventKindServiceMeta event.
s.broadcast(&discoverd.Event{
Service: c.Service,
Kind: discoverd.EventKindServiceMeta,
ServiceMeta: c.Meta,
})
if leaderID != "" {
// Broadcast leader update, if the new instance exists
if inst := s.data.Instances[c.Service][leaderID]; inst != nil {
s.broadcast(&discoverd.Event{
Service: c.Service,
Kind: discoverd.EventKindLeader,
Instance: inst,
})
}
}
return nil
}