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Fix infinite failure on Kubernetes watch #6504

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merged 1 commit into from
Mar 12, 2018
Merged

Fix infinite failure on Kubernetes watch #6504

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1 change: 1 addition & 0 deletions CHANGELOG.asciidoc
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Original file line number Diff line number Diff line change
Expand Up @@ -87,6 +87,7 @@ https://github.com/elastic/beats/compare/v6.0.0-beta2...master[Check the HEAD di
- Fix conditions checking on autodiscover Docker labels. {pull}6412[6412]
- Fix for kafka logger. {pull}6430[6430]
- Remove double slashes in Windows service script. {pull}6491[6491]
- Fix infinite failure on Kubernetes watch {pull}6504[6504]

*Auditbeat*

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23 changes: 22 additions & 1 deletion libbeat/common/kubernetes/watcher.go
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Expand Up @@ -3,6 +3,7 @@ package kubernetes
import (
"context"
"fmt"
"io"
"time"

"github.com/ericchiang/k8s"
Expand All @@ -11,6 +12,9 @@ import (
"github.com/elastic/beats/libbeat/logp"
)

// Max back off time for retries
const maxBackoff = 30 * time.Second

func filterByNode(node string) k8s.Option {
return k8s.QueryParam("fieldSelector", "spec.nodeName="+node)
}
Expand Down Expand Up @@ -161,6 +165,9 @@ func (w *watcher) Start() error {
}

func (w *watcher) watch() {
// Failures counter, do exponential backoff on retries
var failures uint

for {
select {
case <-w.ctx.Done():
Expand All @@ -176,7 +183,8 @@ func (w *watcher) watch() {
//watch failures should be logged and gracefully failed over as metadata retrieval
//should never stop.
logp.Err("kubernetes: Watching API error %v", err)
time.Sleep(time.Second)
backoff(failures)
failures++
continue
}

Expand All @@ -186,8 +194,14 @@ func (w *watcher) watch() {
if err != nil {
logp.Err("kubernetes: Watching API error %v", err)
watcher.Close()
if !(err == io.EOF || err == io.ErrUnexpectedEOF) {
// This is an error event which can be recovered by moving to the latest resource verison
logp.Info("kubernetes: Ignoring event, moving to most recent resource version")
w.lastResourceVersion = ""
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We may need to resync the stored objects, e.g. what would happen if we lose a delete event while we reconnect?

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I've been doing some tests. At least when I reproduce this last resource version is increased by several hundred while no real change happened.

I agree with you @jsoriano, a resync may be needed to guarantee no events are missed during the reconnect.

Still, taking into account the severity of this issue, I'm ok with merging + backporting this as it is, as it improves the current situation (infinite loop + crash). I can do some more research and come up with a resync mechanism afterwards.

What do you think?

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i think we are good to merge this one in.

}
break
}
failures = 0
switch eventType {
case k8s.EventAdded:
w.onAdd(r)
Expand All @@ -205,3 +219,10 @@ func (w *watcher) watch() {
func (w *watcher) Stop() {
w.stop()
}
func backoff(failures uint) {
wait := 1 << failures * time.Second
if wait > maxBackoff {
wait = maxBackoff
}
time.Sleep(wait)
}