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announcer.go
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announcer.go
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// Copyright (c) 2016-2019 Uber Technologies, Inc.
//
// 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
//
// http://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 announcer
import (
"time"
"github.com/uber/kraken/core"
"github.com/uber/kraken/tracker/announceclient"
"github.com/andres-erbsen/clock"
"go.uber.org/atomic"
"go.uber.org/zap"
)
// Config defines Announcer configuration.
type Config struct {
DefaultInterval time.Duration `yaml:"default_interval"`
MaxInterval time.Duration `yaml:"max_interval"`
}
func (c Config) applyDefaults() Config {
if c.DefaultInterval == 0 {
c.DefaultInterval = 5 * time.Second
}
if c.MaxInterval == 0 {
c.MaxInterval = time.Minute
}
return c
}
// Events defines Announcer events.
type Events interface {
AnnounceTick()
}
// Announcer is a thin wrapper around an announceclient.Client which handles
// changes to the announce interval.
type Announcer struct {
config Config
client announceclient.Client
events Events
interval *atomic.Int64
timer *clock.Timer
logger *zap.SugaredLogger
}
// New creates a new Announcer.
func New(
config Config,
client announceclient.Client,
events Events,
clk clock.Clock,
logger *zap.SugaredLogger) *Announcer {
config = config.applyDefaults()
return &Announcer{
config: config,
client: client,
events: events,
interval: atomic.NewInt64(int64(config.DefaultInterval)),
timer: clk.Timer(config.DefaultInterval),
logger: logger,
}
}
// Default creates a default Announcer.
// TODO(evelynl94): make announce interval configurable.
func Default(
client announceclient.Client,
events Events,
clk clock.Clock,
logger *zap.SugaredLogger) *Announcer {
return New(Config{}, client, events, clk, logger)
}
// Announce announces through the underlying client and returns the resulting
// peer handout. Updates the announce interval if it has changed.
func (a *Announcer) Announce(
d core.Digest, h core.InfoHash, complete bool) ([]*core.PeerInfo, error) {
peers, interval, err := a.client.Announce(d, h, complete, announceclient.V1)
if err != nil {
return nil, err
}
if interval == 0 {
// Protect against unset intervals.
interval = a.config.DefaultInterval
}
if interval > a.config.MaxInterval {
// Since the timer is only reset on ticks, a wildly high interval can lock
// down future updates to interval. The max interval protects against a
// mistake in the central authority which will become impossible to correct.
interval = a.config.DefaultInterval
}
if a.interval.Swap(int64(interval)) != int64(interval) {
// Note: updated interval will take effect after next tick.
a.logger.Infof("Announce interval updated to %s", interval)
}
return peers, nil
}
// Ticker emits AnnounceTick events at the current announce interval, which may be
// updated by Announce. Ticker exits when done is closed.
func (a *Announcer) Ticker(done <-chan struct{}) {
for {
select {
case <-a.timer.C:
a.events.AnnounceTick()
a.timer.Reset(time.Duration(a.interval.Load()))
case <-done:
return
}
}
}