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discovery_gossip.go
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/
discovery_gossip.go
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// Copyright (C) 2021 Mya Pitzeruse
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
package cluster
import (
"context"
"github.com/hashicorp/serf/serf"
"go.pitz.tech/lib/logger"
)
// GossipDiscovery uses HashiCorp's Serf library to discover nodes within the cluster. It requires both TCP and UDP
// communication to be available.
type GossipDiscovery struct {
JoinAddress string `json:"join_address" usage:"create a cluster dynamically through a single join address"`
Config *serf.Config `json:"-"`
}
func (g *GossipDiscovery) consume(ctx context.Context, membership *Membership, eventCh chan serf.Event) error {
for {
select {
case <-ctx.Done():
return ctx.Err()
case ev := <-eventCh:
if memberEvent, ok := ev.(serf.MemberEvent); ok {
updatedPeers := make([]string, 0, len(memberEvent.Members))
for _, member := range memberEvent.Members {
updatedPeers = append(updatedPeers, member.Addr.String())
}
switch memberEvent.EventType() {
case serf.EventMemberJoin:
membership.Add(updatedPeers)
case serf.EventMemberLeave, serf.EventMemberFailed:
membership.Left(updatedPeers)
case serf.EventMemberReap:
membership.Remove(updatedPeers)
}
}
}
}
}
func (g *GossipDiscovery) Start(ctx context.Context, membership *Membership) error {
eventCh := make(chan serf.Event, 16)
defer close(eventCh)
log := logger.HashiCorpStdLogger(logger.Extract(ctx))
g.Config.EventCh = eventCh
g.Config.Logger = log
g.Config.MemberlistConfig.Logger = log
serfClient, err := serf.Create(g.Config)
if err != nil {
return err
}
defer func() {
_ = serfClient.Shutdown()
}()
_, err = serfClient.Join([]string{g.JoinAddress}, false)
if err != nil {
return err
}
return g.consume(ctx, membership, eventCh)
}
var _ Discovery = &GossipDiscovery{}