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[Elastic Agent] Improve GRPC stop to be more relaxed. #20118

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merged 3 commits into from
Jul 23, 2020
Merged

[Elastic Agent] Improve GRPC stop to be more relaxed. #20118

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d59c6b5
Improve stop to be more relaxed.
blakerouse Jul 21, 2020
88edb8b
Add changelog.
blakerouse Jul 21, 2020
2f94e13
Merge branch 'master' into agent-grpc-stop-disconnect
blakerouse Jul 23, 2020
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1 change: 1 addition & 0 deletions x-pack/elastic-agent/CHANGELOG.asciidoc
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Original file line number Diff line number Diff line change
Expand Up @@ -52,6 +52,7 @@
- Avoid comparing uncomparable types on enroll {issue}19976[19976]
- Fix issues with merging of elastic-agent.yml and fleet.yml {pull}20026[20026]
- Unzip failures on Windows 8/Windows server 2012 {pull}20088[20088]
- Improve GRPC stop to be more relaxed {pull}20118[20118]

==== New features

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7 changes: 5 additions & 2 deletions x-pack/elastic-agent/pkg/core/server/server.go
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Expand Up @@ -526,6 +526,7 @@ func (as *ApplicationState) WriteConnInfo(w io.Writer) error {
// the application times out during stop and ErrApplication
func (as *ApplicationState) Stop(timeout time.Duration) error {
as.checkinLock.Lock()
wasConn := as.checkinDone != nil
cfgIdx := as.statusConfigIdx
as.expected = proto.StateExpected_STOPPING
as.checkinLock.Unlock()
Expand All @@ -548,8 +549,10 @@ func (as *ApplicationState) Stop(timeout time.Duration) error {
s := as.status
doneChan := as.checkinDone
as.checkinLock.RUnlock()
if s == proto.StateObserved_STOPPING && doneChan == nil {
// sent stopping and now is disconnected (so its stopped)
if (wasConn && doneChan == nil) || (!wasConn && s == proto.StateObserved_STOPPING && doneChan == nil) {
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i'm not sure i follow this. if it was connected and doneChan is nil means it got disconnected this seems ok.
second part means if status of application is stopping and doneChan is nil (got disconnected) then we;re destroying but only in case doneChan was nil before so nothing changed.

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Yes the second case is only in the case that Stop() was called but the client was disconnected from the GRPC at that time (which is very rare, but possible).

So if the client was disconnected from the GPRC at the time Stop() was called, it needs to know that it did receive the stopping state. So it waits for the client to send that it is actually stopping and then it has disconnected. This requires that the client actually reconnect to get the stopping message or timeout occurs, which ever comes first.

In the normal case the wasConn && doneChan == nil will almost always be used in this loop.

Hopefully that it explains it better.

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makes sense thanks

// either occurred
// * client was connected then disconnected on stop
// * client was not connected; connected; received stopping; then disconnected
as.Destroy()
return nil
}
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51 changes: 51 additions & 0 deletions x-pack/elastic-agent/pkg/core/server/server_test.go
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Expand Up @@ -416,6 +416,57 @@ func TestServer_Stop(t *testing.T) {
assert.NoError(t, stopErr)
}

func TestServer_StopJustDisconnect(t *testing.T) {
initConfig := "initial_config"
app := &StubApp{}
srv := createAndStartServer(t, &StubHandler{})
defer srv.Stop()
as, err := srv.Register(app, initConfig)
require.NoError(t, err)
cImpl := &StubClientImpl{}
c := newClientFromApplicationState(t, as, cImpl)
require.NoError(t, c.Start(context.Background()))
defer c.Stop()

// clients should get initial check-ins then set as healthy
require.NoError(t, waitFor(func() error {
if cImpl.Config() != initConfig {
return fmt.Errorf("client never got intial config")
}
return nil
}))
c.Status(proto.StateObserved_HEALTHY, "Running", nil)
assert.NoError(t, waitFor(func() error {
if app.Status() != proto.StateObserved_HEALTHY {
return fmt.Errorf("server never updated currect application state")
}
return nil
}))

// send stop to the client
done := make(chan bool)
var stopErr error
go func() {
stopErr = as.Stop(time.Second * 5)
close(done)
}()

// process of testing the flow
// 1. server sends stop
// 2. client disconnects
require.NoError(t, waitFor(func() error {
if cImpl.Stop() == 0 {
return fmt.Errorf("client never got expected stop")
}
return nil
}))
c.Stop()
<-done

// no error on stop
assert.NoError(t, stopErr)
}

func TestServer_StopTimeout(t *testing.T) {
initConfig := "initial_config"
app := &StubApp{}
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