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delegate.go
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delegate.go
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package cluster
import (
"encoding/json"
"strings"
"github.com/go-kit/kit/log"
"github.com/go-kit/kit/log/level"
"github.com/hashicorp/memberlist"
"github.com/prometheus/client_golang/prometheus"
)
// delegate implements memberlist.Delegate and memberlist.EventDelegate
// and broadcasts its peer's state in the cluster.
type delegate struct {
*memberlist.TransmitLimitedQueue
logger log.Logger
data *data
gossipMsgsReceived prometheus.Counter
gossipClusterMembers prometheus.Gauge
}
func newDelegate(l log.Logger, numNodes func() int, data *data, gossipMsgsReceived prometheus.Counter, gossipClusterMembers prometheus.Gauge) *delegate {
return &delegate{
TransmitLimitedQueue: &memberlist.TransmitLimitedQueue{
NumNodes: numNodes,
RetransmitMult: 3,
},
logger: l,
data: data,
gossipMsgsReceived: gossipMsgsReceived,
gossipClusterMembers: gossipClusterMembers,
}
}
// NodeMeta retrieves meta-data about the current node when broadcasting an alive message.
func (d *delegate) NodeMeta(limit int) []byte {
return []byte{}
}
// NotifyMsg is the callback invoked when a user-level gossip message is received.
func (d *delegate) NotifyMsg(b []byte) {
var data map[string]PeerState
if err := json.Unmarshal(b, &data); err != nil {
level.Error(d.logger).Log("method", "NotifyMsg", "b", strings.TrimSpace(string(b)), "err", err)
return
}
d.gossipMsgsReceived.Inc()
for k, v := range data {
// Removing data is handled by NotifyLeave
d.data.Set(k, v)
}
}
// LocalState is called when gossip fetches local state.
func (d *delegate) LocalState(_ bool) []byte {
b, err := json.Marshal(d.data.Data())
if err != nil {
panic(err)
}
return b
}
func (d *delegate) MergeRemoteState(buf []byte, _ bool) {
var data map[string]PeerState
if err := json.Unmarshal(buf, &data); err != nil {
level.Error(d.logger).Log("method", "MergeRemoteState", "err", err)
return
}
for k, v := range data {
// Removing data is handled by NotifyLeave
d.data.Set(k, v)
}
}
// NotifyJoin is called if a peer joins the cluster.
func (d *delegate) NotifyJoin(n *memberlist.Node) {
d.gossipClusterMembers.Inc()
level.Debug(d.logger).Log("received", "NotifyJoin", "node", n.Name, "addr", n.Address())
}
// NotifyLeave is called if a peer leaves the cluster.
func (d *delegate) NotifyLeave(n *memberlist.Node) {
d.gossipClusterMembers.Dec()
level.Debug(d.logger).Log("received", "NotifyLeave", "node", n.Name, "addr", n.Address())
d.data.Del(n.Name)
}
// NotifyUpdate is called if a cluster peer gets updated.
func (d *delegate) NotifyUpdate(n *memberlist.Node) {
level.Debug(d.logger).Log("received", "NotifyUpdate", "node", n.Name, "addr", n.Address())
}