alertmanager-irc-relay/reconciler.go

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// Copyright 2021 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package main
import (
"context"
"sync"
"time"
irc "github.com/fluffle/goirc/client"
"github.com/google/alertmanager-irc-relay/logging"
)
const (
ircJoinWaitSecs = 10
ircJoinMaxBackoffSecs = 300
ircJoinBackoffResetSecs = 1800
)
type channelState struct {
channel IRCChannel
client *irc.Conn
delayer Delayer
timeTeller TimeTeller
joinDone chan struct{} // joined when channel is closed
joined bool
joinUnsetSignal chan bool
mu sync.Mutex
}
func newChannelState(channel *IRCChannel, client *irc.Conn, delayerMaker DelayerMaker, timeTeller TimeTeller) *channelState {
delayer := delayerMaker.NewDelayer(ircJoinMaxBackoffSecs, ircJoinBackoffResetSecs, time.Second)
return &channelState{
channel: *channel,
client: client,
delayer: delayer,
timeTeller: timeTeller,
joinDone: make(chan struct{}),
joined: false,
joinUnsetSignal: make(chan bool),
}
}
func (c *channelState) JoinDone() <-chan struct{} {
c.mu.Lock()
defer c.mu.Unlock()
return c.joinDone
}
func (c *channelState) SetJoined() {
c.mu.Lock()
defer c.mu.Unlock()
if c.joined == true {
logging.Warn("Not setting JOIN state on channel %s: already set", c.channel.Name)
return
}
logging.Info("Setting JOIN state on channel %s", c.channel.Name)
c.joined = true
close(c.joinDone)
}
func (c *channelState) UnsetJoined() {
c.mu.Lock()
defer c.mu.Unlock()
if c.joined == false {
logging.Warn("Not removing JOIN state on channel %s: already not set", c.channel.Name)
return
}
logging.Info("Removing JOIN state on channel %s", c.channel.Name)
c.joined = false
c.joinDone = make(chan struct{})
// eventually poke monitor routine
select {
case c.joinUnsetSignal <- true:
default:
}
}
func (c *channelState) join(ctx context.Context) {
logging.Info("Channel %s monitor: waiting to join", c.channel.Name)
if ok := c.delayer.DelayContext(ctx); !ok {
return
}
// Try to unban ourselves, just in case
c.client.Privmsgf("ChanServ", "UNBAN %s", c.channel.Name)
c.client.Join(c.channel.Name, c.channel.Password)
logging.Info("Channel %s monitor: join request sent", c.channel.Name)
select {
case <-c.JoinDone():
logging.Info("Channel %s monitor: join succeeded", c.channel.Name)
case <-c.timeTeller.After(ircJoinWaitSecs * time.Second):
logging.Warn("Channel %s monitor: could not join after %d seconds, will retry", c.channel.Name, ircJoinWaitSecs)
case <-ctx.Done():
logging.Info("Channel %s monitor: context canceled while waiting for join", c.channel.Name)
}
}
func (c *channelState) monitorJoinUnset(ctx context.Context) {
select {
case <-c.joinUnsetSignal:
logging.Info("Channel %s monitor: channel no longer joined", c.channel.Name)
case <-ctx.Done():
logging.Info("Channel %s monitor: context canceled while monitoring", c.channel.Name)
}
}
func (c *channelState) Monitor(ctx context.Context, wg *sync.WaitGroup) {
defer wg.Done()
joined := func() bool {
c.mu.Lock()
defer c.mu.Unlock()
return c.joined
}
for ctx.Err() != context.Canceled {
if !joined() {
c.join(ctx)
} else {
c.monitorJoinUnset(ctx)
}
}
}
type ChannelReconciler struct {
preJoinChannels []IRCChannel
client *irc.Conn
delayerMaker DelayerMaker
timeTeller TimeTeller
channels map[string]*channelState
stopCtx context.Context
stopCtxCancel context.CancelFunc
stopWg sync.WaitGroup
mu sync.Mutex
}
func NewChannelReconciler(config *Config, client *irc.Conn, delayerMaker DelayerMaker, timeTeller TimeTeller) *ChannelReconciler {
reconciler := &ChannelReconciler{
preJoinChannels: config.IRCChannels,
client: client,
delayerMaker: delayerMaker,
timeTeller: timeTeller,
channels: make(map[string]*channelState),
}
reconciler.registerHandlers()
return reconciler
}
func (r *ChannelReconciler) registerHandlers() {
r.client.HandleFunc(irc.JOIN,
func(_ *irc.Conn, line *irc.Line) {
r.HandleJoin(line.Nick, line.Args[0])
})
r.client.HandleFunc(irc.KICK,
func(_ *irc.Conn, line *irc.Line) {
r.HandleKick(line.Args[1], line.Args[0])
})
}
func (r *ChannelReconciler) HandleJoin(nick string, channel string) {
r.mu.Lock()
defer r.mu.Unlock()
if nick != r.client.Me().Nick {
// received join info for somebody else
return
}
logging.Info("Received JOIN confirmation for channel %s", channel)
c, ok := r.channels[channel]
if !ok {
logging.Warn("Not processing JOIN for channel %s: unknown channel", channel)
return
}
c.SetJoined()
}
func (r *ChannelReconciler) HandleKick(nick string, channel string) {
r.mu.Lock()
defer r.mu.Unlock()
if nick != r.client.Me().Nick {
// received kick info for somebody else
return
}
logging.Info("Received KICK for channel %s", channel)
c, ok := r.channels[channel]
if !ok {
logging.Warn("Not processing KICK for channel %s: unknown channel", channel)
return
}
c.UnsetJoined()
}
func (r *ChannelReconciler) unsafeAddChannel(channel *IRCChannel) *channelState {
c := newChannelState(channel, r.client, r.delayerMaker, r.timeTeller)
r.stopWg.Add(1)
go c.Monitor(r.stopCtx, &r.stopWg)
r.channels[channel.Name] = c
return c
}
func (r *ChannelReconciler) JoinChannel(channel string) (bool, <-chan struct{}) {
r.mu.Lock()
defer r.mu.Unlock()
c, ok := r.channels[channel]
if !ok {
logging.Info("Request to JOIN new channel %s", channel)
c = r.unsafeAddChannel(&IRCChannel{Name: channel})
}
select {
case <-c.JoinDone():
return true, nil
default:
return false, c.JoinDone()
}
}
func (r *ChannelReconciler) unsafeStop() {
if r.stopCtxCancel == nil {
// calling stop before first start, ignoring
return
}
r.stopCtxCancel()
r.stopWg.Wait()
r.channels = make(map[string]*channelState)
}
func (r *ChannelReconciler) Stop() {
r.mu.Lock()
defer r.mu.Unlock()
r.unsafeStop()
}
func (r *ChannelReconciler) Start(ctx context.Context) {
r.mu.Lock()
defer r.mu.Unlock()
r.unsafeStop()
r.stopCtx, r.stopCtxCancel = context.WithCancel(ctx)
for _, channel := range r.preJoinChannels {
r.unsafeAddChannel(&channel)
}
}