Bugfix/zenko 4912

[benzekrimaha]

Issue : ZENKO-4912

[bert-e]

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[bert-e]

Waiting for approval

The following approvals are needed before I can proceed with the merge:

• the author

• 2 peers

[francoisferrand]

reminder to rebase: this should be the last commit of the PR (where we will make the release)

[francoisferrand]

nit: indent to improve readabiltiy...

Suggested change

	group by(rs_nm)(count by (rs_nm, pod)(mongodb_rs_members_state{namespace="${namespace}", pod=~"${service}.*", member_state="SECONDARY"}) != (${replicas} - 1) )
	group by(rs_nm) (
	count by(rs_nm, pod) (mongodb_rs_members_state{namespace="${namespace}", pod=~"${service}.*", member_state="SECONDARY"})
	!= (${replicas} - 1)
	)

[francoisferrand]

when this serie disappears, the other series will actually change as well: as the remaining pods will not report on its status anymore... and the state reporte looks strange :/

• On "startup", we should have series : everything is running fine (3 pods having the status of 3 members)
• Then one pod "crashes" : the 3 associated series stop
• Then the other pods update their "vision" of the cluster : they either report a different member state (not reachable?) or drop the member completely (not sure exactly what happens)

[benzekrimaha]

from what I saw the state is (not reachable/healthy) , the test was updated accordingly

[francoisferrand]

every metric from pod="data-db-mongodb-sharded-shard0-data-2" should be removed when we simulate the pod crashing...

so i guess time series should look something like this:

# First pod
- series: member_state{pod="data-0", state="PRIMARY", member_idx="data-0"}
   values: 1x10 1x10
- series: member_state{pod="data-0", state="SECONDARY", member_idx="data-1"}
   values: 2x10 2x10
- series: member_state{pod="data-0", state="SECONDARY", member_idx="data-2"}
   values: 2x10 stale      # `stale` (i.e. not present) after the 10s sample
- series: member_state{pod="data-0", state="(not reachable/healthy)", member_idx="data-2"}
   values: _x10 8x10      # appears from the 11s sample
# Second pod
- series: member_state{pod="data-1", state="PRIMARY", member_idx="data-0"}
   values: 1x10 1x10
- series: member_state{pod="data-1", state="SECONDARY", member_idx="data-1"}
   values: 2x10 2x10
- series: member_state{pod="data-1", state="SECONDARY", member_idx="data-2"}
   values: 2x10 stale      # `stale` (i.e. not present) after the 10s sample
- series: member_state{pod="data-1", state="(not reachable/healthy)", member_idx="data-2"}
   values: _x10 8x10      # appears from the 11s sample
# Third pod : stops responding after 10th sample
- series: member_state{pod="data-2", state="PRIMARY", member_idx="data-0"}
   values: 1x10 stale
- series: member_state{pod="data-2", state="SECONDARY", member_idx="data-1"}
   values: 2x10 stale
- series: member_state{pod="data-2", state="SECONDARY", member_idx="data-2"}
   values: 2x10 stale

[benzekrimaha]

Providing this : series: member_state{pod="data-0", state="SECONDARY", member_idx="data-2"}
values: 2x10 stale # stale (i.e. not present) after the 10s sample

will cause the expression to return 2 => expected number of secondaries as it's not taking the state="(not reachable/healthy)" metric

[francoisferrand]

AFAIU, stale removes the metric series, which should be what really happens:

• the serie with state label equal to secondary (and value 2) stops
• another serie starts with state label equal to (not reachable/healthy) and value 8

(since one label value changes, this is really another serie : even if [as human] we think it is the same one...)

[francoisferrand]

LGTM, but alert test fail...

[francoisferrand]

LGTM, minor test improvements : please rebase/cleanup before approving

[benzekrimaha]

/approve

[bert-e]

In the queue

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• ✔️ development/2.10

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• development/2.5
• development/2.6
• development/2.7
• development/2.8
• development/2.9

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The following options are set: approve

[bert-e]

I have successfully merged the changeset of this pull request
into targetted development branches:

• ✔️ development/2.10

The following branches have NOT changed:

• development/2.5
• development/2.6
• development/2.7
• development/2.8
• development/2.9

Please check the status of the associated issue ZENKO-4912.

Goodbye benzekrimaha.