[Flaky Test] pull-gardener-extension-shoot-rsyslog-relp-e2e-kind due to logs still getting sent after disabling the extension

[plkokanov]

How to categorize this issue?

/area testing
/kind flake

Which test(s)/suite(s) are flaking:
The Shoot Rsyslog Relp Extension Tests shoot-rsyslog-relp extension with tls and openssl enabled [It] Create Shoot, enable shoot-rsyslog-relp extension then disable it and delete Shoot [tls-enabled] part of pull-gardener-extension-shoot-rsyslog-relp-e2e-kind test fails with the following error:

CI link:
https://prow.gardener.cloud/view/gs/gardener-prow/pr-logs/pull/gardener_gardener-extension-shoot-rsyslog-relp/193/pull-gardener-extension-shoot-rsyslog-relp-e2e-kind/1859607390651944960

Reason for failure:

Shoot Rsyslog Relp Extension Tests shoot-rsyslog-relp extension with tls and openssl enabled [It] Create Shoot, enable shoot-rsyslog-relp extension then disable it and delete Shoot [tls-enabled]
...
...
  [FAILED] Timed out after 30.001s.
  Expected to successfully generate logs for node machine-shoot--local--e2e-rslog-tls-local-68576-blcwr and logs to NOT be present in rsyslog-relp-echo-server
  The function passed to Eventually failed at /home/prow/go/src/github.com/gardener/gardener-extension-shoot-rsyslog-relp/test/common/verifier.go:176 with:
  Expected
      <[]string | len:2, cap:2>: [
          " local e2e-rslog-hib f01243ba-7ae8-420b-ac59-70d0664ac13d machine-shoot--local--e2e-rslog-hib-local-7bcd6-pvgzm 9 test-program[11541]: 2024-11-21T15:11:46.977421+00:00 11541 -  this should get sent to echo server ",
          " -- MARK --",
      ]

The log " local e2e-rslog-hib f01243ba-7ae8-420b-ac59-70d0664ac13d machine-shoot--local--e2e-rslog-hib-local-7bcd6-pvgzm 9 test-program[11541]: 2024-11-21T15:11:46.977421+00:00 11541 - this should get sent to echo server " should be sent when checking if the rsyslog-relp service is properly configured on the shoot's nodes:

gardener-extension-shoot-rsyslog-relp/test/common/verifier.go

Lines 82 to 87 in a2645ee

	v.verifyLogsAreForwardedToEchoServer(
	ctx,
	logEntry{program: "test-program", severity: "1", message: "this should get sent to echo server", shouldBeForwarded: true},
	logEntry{program: "test-program", severity: "3", message: "this should not get sent to echo server", shouldBeForwarded: false},
	logEntry{program: "other-program", severity: "1", message: "this should not get sent to echo server", shouldBeForwarded: false},
	)

However, it appears to have been either delayed or resent after the extension was disabled, and was included in the logs fetched during the verification that no logs should be sent:

gardener-extension-shoot-rsyslog-relp/test/common/verifier.go

Lines 154 to 178 in a2645ee

	func (v *Verifier) verifyThatLogsAreNotForwardedToEchoServer(ctx context.Context, logEntries ...logEntry) {
	timeBeforeLogGeneration := metav1.Now()
	EventuallyWithOffset(2, func() error {
	return v.generateLogs(ctx, logEntries)
	}).WithTimeout(30*time.Second).WithPolling(10*time.Second).WithContext(ctx).Should(Succeed(), fmt.Sprintf("Expected to successfully generate logs for node %s", v.nodeName))
	By("Wait 30 seconds before checking for logs")
	timer := time.NewTimer(30 * time.Second)
	select {
	case <-ctx.Done():
	Fail("context deadline exceeded while waiting to check for logs")
	case <-timer.C:
	}
	By("Verify that there are no logs")
	EventuallyWithOffset(2, func(g Gomega) {
	logLines, err := v.getLogs(ctx, timeBeforeLogGeneration)
	g.Expect(err).NotTo(HaveOccurred())
	// Rsyslog outputs a "-- MARK --" message as a form of heartbeat each 1200 seconds (by default) to indicate that it is working properly.
	// This log comes from the rsyslog server itself and must be ignored when checking if there were no logs sent from the rsyslog clients.
	// ContainSubstring is used as there could be spaces at the start or end of the log message depending on the template with which the
	// rsyslog server is configured.
	g.Expect(logLines).To(Or(BeEmpty(), ConsistOf(ContainSubstring("-- MARK --"))))
	}).WithTimeout(30*time.Second).WithPolling(10*time.Second).WithContext(ctx).Should(Succeed(), fmt.Sprintf("Expected to successfully generate logs for node %s and logs to NOT be present in rsyslog-relp-echo-server", v.nodeName))
	}

Checking the test logs, the extension gets disabled at 15:10:45.742, however the time of this log entry is from 15:11:46.977

  STEP: Disable the shoot-rsyslog-relp extension @ 11/21/24 15:10:45.742
  {"level":"info","ts":"2024-11-21T15:10:45.777Z","logger":"test","msg":"Shoot is not yet reconciled","shoot":{"name":"e2e-rslog-tls","namespace":"garden-local"},"reason":"shoot generation did not equal observed generation"}
  {"level":"info","ts":"2024-11-21T15:10:45.777Z","logger":"test","msg":"Last Operation","shoot":{"name":"e2e-rslog-tls","namespace":"garden-local"},"lastOperation":"&LastOperation{Description:Shoot cluster has been successfully reconciled.,LastUpdateTime:2024-11-21 15:09:58 +0000 UTC,Progress:100,State:Succeeded,Type:Reconcile,}"}
  {"level":"info","ts":"2024-11-21T15:11:15.782Z","logger":"test","msg":"Shoot is not yet reconciled","shoot":{"name":"e2e-rslog-tls","namespace":"garden-local"},"reason":"condition type ControlPlaneHealthy is not true yet, had message Deployment \"gardener-resource-manager\" is unhealthy: condition \"Available\" has invalid status False (expected True) due to MinimumReplicasUnavailable: Deployment does not have minimum availability. with reason DeploymentUnhealthy"}
  {"level":"info","ts":"2024-11-21T15:11:15.782Z","logger":"test","msg":"Last Operation","shoot":{"name":"e2e-rslog-tls","namespace":"garden-local"},"lastOperation":"&LastOperation{Description:Shoot cluster has been successfully reconciled.,LastUpdateTime:2024-11-21 15:11:12 +0000 UTC,Progress:100,State:Succeeded,Type:Reconcile,}"}
  {"level":"info","ts":"2024-11-21T15:11:45.789Z","logger":"test","msg":"Shoot was successfully updated","shoot":{"name":"e2e-rslog-tls","namespace":"garden-local"}}
  STEP: Verify that shoot-rsyslog-relp extension is disabled @ 11/21/24 15:11:45.789
  {"level":"info","ts":"2024-11-21T15:11:45.813Z","logger":"test","msg":"Waiting for Pod to be ready","pod":{"name":"rootpod-r5m","namespace":"kube-system"}}
  {"level":"info","ts":"2024-11-21T15:11:50.816Z","logger":"test","msg":"Pod is ready now","pod":{"name":"rootpod-r5m","namespace":"kube-system"}}
  STEP: Wait 30 seconds before checking for logs @ 11/21/24 15:11:51.461
  STEP: Verify that there are no logs @ 11/21/24 15:12:21.461

Anything else we need to know:
N/A