open-consul/watch/plan.go

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package watch
import (
"fmt"
"log"
"os"
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"reflect"
"time"
consulapi "github.com/hashicorp/consul/api"
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)
const (
// retryInterval is the base retry value
retryInterval = 5 * time.Second
// maximum back off time, this is to prevent
// exponential runaway
maxBackoffTime = 180 * time.Second
)
// Run is used to run a watch plan
func (p *WatchPlan) Run(address string) error {
// Setup the client
p.address = address
conf := consulapi.DefaultConfig()
conf.Address = address
conf.Datacenter = p.Datacenter
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conf.Token = p.Token
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client, err := consulapi.NewClient(conf)
if err != nil {
return fmt.Errorf("Failed to connect to agent: %v", err)
}
p.client = client
// Create the logger
output := p.LogOutput
if output == nil {
output = os.Stderr
}
logger := log.New(output, "", log.LstdFlags)
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// Loop until we are canceled
failures := 0
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OUTER:
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for !p.shouldStop() {
// Invoke the handler
index, result, err := p.Func(p)
// Check if we should terminate since the function
// could have blocked for a while
if p.shouldStop() {
break
}
// Handle an error in the watch function
if err != nil {
// Perform an exponential backoff
failures++
retry := retryInterval * time.Duration(failures*failures)
if retry > maxBackoffTime {
retry = maxBackoffTime
}
logger.Printf("consul.watch: Watch (type: %s) errored: %v, retry in %v",
p.Type, err, retry)
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select {
case <-time.After(retry):
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continue OUTER
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case <-p.stopCh:
return nil
}
}
// Clear the failures
failures = 0
// If the index is unchanged do nothing
if index == p.lastIndex {
continue
}
// Update the index, look for change
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oldIndex := p.lastIndex
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p.lastIndex = index
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if oldIndex != 0 && reflect.DeepEqual(p.lastResult, result) {
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continue
}
// Handle the updated result
p.lastResult = result
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if p.Handler != nil {
p.Handler(index, result)
}
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}
return nil
}
// Stop is used to stop running the watch plan
func (p *WatchPlan) Stop() {
p.stopLock.Lock()
defer p.stopLock.Unlock()
if p.stop {
return
}
p.stop = true
close(p.stopCh)
}
func (p *WatchPlan) shouldStop() bool {
select {
case <-p.stopCh:
return true
default:
return false
}
}