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docs: update vmalert troubleshooting docs
* rm recommendation to keep look-behind window empty, as it is not correct * mention the change of default value for `-search.latencyOffset` Signed-off-by: hagen1778 <roman@victoriametrics.com>
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@ -822,13 +822,11 @@ may get empty response from the datasource and produce empty recording rules or
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<img alt="vmalert evaluation when data is delayed" src="vmalert_ts_data_delay.gif">
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Try the following recommendations to reduce the chance of hitting the data delay issue:
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* Always configure group's `-evaluationInterval` to be bigger or at least equal to
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[time series resolution](https://docs.victoriametrics.com/keyConcepts.html#time-series-resolution);
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* Ensure that `[duration]` value is at least twice bigger than
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[time series resolution](https://docs.victoriametrics.com/keyConcepts.html#time-series-resolution). For example,
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if expression is `rate(my_metric[2m]) > 0` then ensure that `my_metric` resolution is at least `1m` or better `30s`.
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If you use VictoriaMetrics as datasource, `[duration]` can be omitted and VictoriaMetrics will adjust it automatically.
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* Extend `[duration]` in expr to help tolerate the delay. For example, `max_over_time(errors_total[10m]) > 0` will be active even if there is no data in datasource for last `9m`.
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* If [time series resolution](https://docs.victoriametrics.com/keyConcepts.html#time-series-resolution)
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in datasource is inconsistent or `>=5min` - try changing vmalerts `-datasource.queryStep` command-line flag to specify
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@ -841,8 +839,8 @@ By default, recently written samples to VictoriaMetrics [aren't visible for quer
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for up to 30s (see `-search.latencyOffset` command-line flag at vmselect or VictoriaMetrics single-node). Such delay is needed to eliminate risk of
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incomplete data on the moment of querying, due to chance that metrics collectors won't be able to deliver that data in time.
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To compensate the latency in timestamps for produced evaluation results, `-rule.evalDelay` is also set to `30s` by default.
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If you expect data to be delayed for longer intervals (it gets buffered, queued, or just network is slow sometimes)
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- consider increasing the `-rule.evalDelay` value accordingly.
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If you expect data to be delayed for longer intervals (it gets buffered, queued, or just network is slow sometimes),
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or you changed default value of `-search.latencyOffset` - consider increasing the `-rule.evalDelay` value accordingly.
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### Alerts state
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