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Documentation: Further improve etcdMembersDown alert

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Before this change, the default window for the etcdMembersDown network failure
rate function was recently changed to 1 minute. While this helps detect a etcd
recovery more quickly, it depends on scrape intervals of <= 15s to collect
sufficient data points for the rate function. In practice, an interval of >= 30s
is more typical, which causes the rate function to be less accurate.

This patch increases the window to 2m, which is a compromise between the
original value of 3m and the 1m change introuced with 2aa5684, and should
accomodate more typical scrape intervals.

To offset the window change and to further improve the chance that the alert
will only fire when etcd is truly dead, this patch changes the `for` clause from
3m to 10m. The rationale is as follows:

1. There can be significant variance in durations following a reboot before etcd
is scraped and detected as available.

2. A conservative trigger like 10m seems less likely to produce a false alarm in
the face of such variance.

3. In this alerting situation, if the outage is real, it seems unlikely that an
additional 7 minutes of delay before (for example) paging somebody will make a
significant impact on the overall response.
This commit is contained in:
Dan Mace 2020-07-27 17:23:04 -04:00
parent cc564110bd
commit cd3df73944
2 changed files with 18 additions and 17 deletions
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9
Documentation/etcd-mixin/mixin.libsonnet
View File

@ -7,6 +7,9 @@
// instances are deployed on K8s, you will likely want to change
// this to 'instance, pod'.
etcd_instance_labels: 'instance',
// scrape_interval_seconds is the global scrape interval which can be
// used to dynamically adjust rate windows as a function of the interval.
scrape_interval_seconds: 30,
},
prometheusAlerts+:: {
@ -21,12 +24,12 @@
sum without (%(etcd_instance_labels)s) (up{%(etcd_selector)s} == bool 0)
or
count without (To) (
sum without (%(etcd_instance_labels)s) (rate(etcd_network_peer_sent_failures_total{%(etcd_selector)s}[1m])) > 0.01
sum without (%(etcd_instance_labels)s) (rate(etcd_network_peer_sent_failures_total{%(etcd_selector)s}[%(network_failure_range)ss])) > 0.01
)
)
> 0
||| % $._config,
'for': '3m',
||| % {etcd_instance_labels: $._config.etcd_instance_labels, etcd_selector: $._config.etcd_selector, network_failure_range: $._config.scrape_interval_seconds*4},
'for': '10m',
labels: {
severity: 'critical',
},

26
Documentation/etcd-mixin/test.yaml
View File

@ -17,16 +17,16 @@ tests:
alertname: etcdInsufficientMembers
- eval_time: 5m
alertname: etcdInsufficientMembers
- eval_time: 5m
- eval_time: 12m
alertname: etcdMembersDown
- eval_time: 7m
- eval_time: 14m
alertname: etcdMembersDown
exp_alerts:
- exp_labels:
job: etcd
severity: critical
exp_annotations:
message: 'etcd cluster "etcd": members are down (1).'
message: 'etcd cluster "etcd": members are down (3).'
- eval_time: 7m
alertname: etcdInsufficientMembers
- eval_time: 11m
@ -49,33 +49,31 @@ tests:
- interval: 1m
input_series:
- series: 'up{job="etcd",instance="10.10.10.0"}'
values: '1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0'
values: '1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0'
- series: 'up{job="etcd",instance="10.10.10.1"}'
values: '1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0'
values: '1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0'
- series: 'up{job="etcd",instance="10.10.10.2"}'
values: '1 1 1 1 0 0 0 0'
values: '1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0'
alert_rule_test:
- eval_time: 10m
- eval_time: 14m
alertname: etcdMembersDown
exp_alerts:
- exp_labels:
job: etcd
severity: critical
exp_annotations:
message: 'etcd cluster "etcd": members are down (2).'
message: 'etcd cluster "etcd": members are down (3).'
- interval: 1m
input_series:
- series: 'up{job="etcd",instance="10.10.10.0"}'
values: '1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0'
values: '1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0'
- series: 'up{job="etcd",instance="10.10.10.1"}'
values: '1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0'
values: '1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0'
- series: 'etcd_network_peer_sent_failures_total{To="member-1",job="etcd",endpoint="test"}'
values: '0 0 1 2 3 4 5 6 7 8 9 10'
values: '0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18'
alert_rule_test:
- eval_time: 4m
alertname: etcdMembersDown
- eval_time: 6m
- eval_time: 13m
alertname: etcdMembersDown
exp_alerts:
- exp_labels: