Bug 2013646

Summary: fsync controller will show false positive if gaps in metrics are observed.
Product: OpenShift Container Platform Reporter: Lili Cosic <lcosic>
Component: EtcdAssignee: Nobody <nobody>
Status: CLOSED ERRATA QA Contact: Sandeep <skundu>
Severity: medium Docs Contact:
Priority: unspecified    
Version: 4.7CC: geliu, skundu
Target Milestone: ---   
Target Release: 4.10.0   
Hardware: Unspecified   
OS: Unspecified   
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Fixed In Version: Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of: 2008175 Environment:
Last Closed: 2022-03-10 16:19:33 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 2008175    

Description Lili Cosic 2021-10-13 13:02:17 UTC 
+++ This bug was initially created as a clone of Bug #2008175 +++

Description of problem: If gaps in metrics are observed by fsync controller they can provide false positives for leader election growth over time series. This can result in sending admin on an invalid path of etcd performance triage.

> Detected leader change increase of 1.25 over 5 minutes on "BareMetal"; disk metrics are: etcd-nfvpe-12.oot.lab.eng.bos.redhat.com=0.0025688888888888875,etcd-nfvpe-13.oot.lab.eng.bos.redhat.com=0.0018824444444444331,etcd-nfvpe-02.oot.lab.eng.bos.redhat.com=0.001912424242424239


The image below shows leader elections(green) with spikes in leader elections(blue) as a result of the query.

https://user-images.githubusercontent.com/1249749/134918692-43ca6cf0-4fb0-4ee3-8735-f5d035d56170.png

This metric query clearly shows the gaps in the collection of metrics from possible networking issues.

https://user-images.githubusercontent.com/1249749/134919312-f62591ee-57df-41de-a313-545e207d89ad.png

Version-Release number of selected component (if applicable):


How reproducible: given condition 100%


Steps to Reproduce:
1. generate gaps in metrics collection by disrupting networking
2. review events from cluster-etcd-operator namespace for Detected leader change increase events.

3. verify etcd is not actually experiencing leader elections `etcd_server_leader_changes_seen_total`

Actual results: leader elections are fasley reported by fsync controller 


Expected results: fsync controller should event only with an actual observation of the issue.


Additional info:
Comment 4 Sandeep 2022-02-17 12:06:31 UTC 
oc get clusterversion
NAME      VERSION                              AVAILABLE   PROGRESSING   SINCE   STATUS
version   4.10.0-0.nightly-2022-02-16-171622   True        False         5h23m   Cluster version is 4.10.0-0.nightly-2022-02-16-171622


sh-4.4# etcdctl endpoint status -w table
+-----------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
|       ENDPOINT        |        ID        | VERSION | DB SIZE | IS LEADER | IS LEARNER | RAFT TERM | RAFT INDEX | RAFT APPLIED INDEX | ERRORS |
+-----------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
| https://10.0.0.3:2379 | 6951e8940830cac5 |   3.5.0 |   78 MB |      true |      false |        10 |     172448 |             172448 |        |
| https://10.0.0.4:2379 | 5ce2c3932bb984e2 |   3.5.0 |   78 MB |     false |      false |        10 |     172448 |             172448 |        |
| https://10.0.0.5:2379 | 41849292a8dfd31b |   3.5.0 |   78 MB |     false |      false |        10 |     172449 |             172449 |        |
+-----------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+

Changed the leader few times (more than 2).
sh-4.4# etcdctl endpoint status -w table
+-----------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
|       ENDPOINT        |        ID        | VERSION | DB SIZE | IS LEADER | IS LEARNER | RAFT TERM | RAFT INDEX | RAFT APPLIED INDEX | ERRORS |
+-----------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
| https://10.0.0.3:2379 | 6951e8940830cac5 |   3.5.0 |   78 MB |     false |      false |        10 |     172448 |             172448 |        |
| https://10.0.0.4:2379 | 5ce2c3932bb984e2 |   3.5.0 |   78 MB |      true |      false |        10 |     172448 |             172448 |        |
| https://10.0.0.5:2379 | 41849292a8dfd31b |   3.5.0 |   78 MB |     false |      false |        10 |     172449 |             172449 |        |
+-----------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+


the rules:etcd_server_leader_changes_seen_total are getting updated.


$ oc -n openshift-monitoring exec -c prometheus prometheus-k8s-0 -- curl -k -H "Authorization: Bearer sha256~lIpa1V2jbdLyrNBeRvihrXphl-b5mglXOmAsyEKYM9o" 'https://prometheus-k8s.openshift-monitoring.svc:9091/api/v1/query?query=etcd_server_leader_changes_seen_total' | jq
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   851    0   851    0     0  47277      0 --:--:-- --:--:-- --:--:-- 47277
{
  "status": "success",
  "data": {
    "resultType": "vector",
    "result": [
      {
        "metric": {
          "__name__": "etcd_server_leader_changes_seen_total",
          "endpoint": "etcd-metrics",
          "instance": "10.0.141.21:9979",
          "job": "etcd",
          "namespace": "openshift-etcd",
          "pod": "etcd-ip-10-0-141-21.us-east-2.compute.internal",
          "service": "etcd"
        },
        "value": [
          1637311116.534,
          "3"
        ]
      },
      {
        "metric": {
          "__name__": "etcd_server_leader_changes_seen_total",
          "endpoint": "etcd-metrics",
          "instance": "10.0.170.2:9979",
          "job": "etcd",
          "namespace": "openshift-etcd",
          "pod": "etcd-ip-10-0-170-2.us-east-2.compute.internal",
          "service": "etcd"
        },
        "value": [
          1637311116.534,
          "1"
        ]
      },
      {
        "metric": {
          "__name__": "etcd_server_leader_changes_seen_total",
          "endpoint": "etcd-metrics",
          "instance": "10.0.220.249:9979",
          "job": "etcd",
          "namespace": "openshift-etcd",
          "pod": "etcd-ip-10-0-220-249.us-east-2.compute.internal",
          "service": "etcd"
        },
        "value": [
          1637311116.534,
          "2"
        ]
      }
    ]
  }
}



$ oc -n openshift-monitoring exec -c prometheus prometheus-k8s-0 -- curl -k -H "Authorization: Bearer sha256~lIpa1V2jbdLyrNBeRvihrXphl-b5mglXOmAsyEKYM9o" 'https://prometheus-k8s.openshift-monitoring.svc:9091/api/v1/query?query=etcd_server_leader_changes_seen_total' | jq
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   851    0   851    0     0  56733      0 --:--:-- --:--:-- --:--:-- 56733
{
  "status": "success",
  "data": {
    "resultType": "vector",
    "result": [
      {
        "metric": {
          "__name__": "etcd_server_leader_changes_seen_total",
          "endpoint": "etcd-metrics",
          "instance": "10.0.141.21:9979",
          "job": "etcd",
          "namespace": "openshift-etcd",
          "pod": "etcd-ip-10-0-141-21.us-east-2.compute.internal",
          "service": "etcd"
        },
        "value": [
          1637311282.715,
          "1"
        ]
      },
      {
        "metric": {
          "__name__": "etcd_server_leader_changes_seen_total",
          "endpoint": "etcd-metrics",
          "instance": "10.0.170.2:9979",
          "job": "etcd",
          "namespace": "openshift-etcd",
          "pod": "etcd-ip-10-0-170-2.us-east-2.compute.internal",
          "service": "etcd"
        },
        "value": [
          1637311282.715,
          "2"
        ]
      },
      {
        "metric": {
          "__name__": "etcd_server_leader_changes_seen_total",
          "endpoint": "etcd-metrics",
          "instance": "10.0.220.249:9979",
          "job": "etcd",
          "namespace": "openshift-etcd",
          "pod": "etcd-ip-10-0-220-249.us-east-2.compute.internal",
          "service": "etcd"
        },
        "value": [
          1637311282.715,
          "3"
        ]
      }
    ]
  }
}
Comment 6 errata-xmlrpc 2022-03-10 16:19:33 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (Moderate: OpenShift Container Platform 4.10.3 security update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHSA-2022:0056