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Merge pull request #12998 from ringerc/docs-instant-vector-staleness

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Docs: Refer to staleness in instant vector documentation
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Björn Rabenstein 2024-09-26 14:52:34 +02:00 committed by GitHub
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docs/querying/basics.md
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@ -109,8 +109,16 @@ single sample value for each at a given timestamp (point in time). In the simpl
form, only a metric name is specified, which results in an instant vector
containing elements for all time series that have this metric name.
The value returned will be that of the most recent sample at or before the
query's evaluation timestamp (in the case of an
[instant query](api.md#instant-queries))
or the current step within the query (in the case of a
[range query](api.md/#range-queries)).
The [`@` modifier](#modifier) allows overriding the timestamp relative to which
the selection takes place. Time series are only returned if their most recent sample is less than the [lookback period](#staleness) ago.
This example selects all time series that have the `http_requests_total` metric
name:
name, returning the most recent sample for each:
http_requests_total
@ -359,7 +367,8 @@ cases like aggregation (`sum`, `avg`, and so on), where multiple aggregated
time series do not precisely align in time. Because of their independence,
Prometheus needs to assign a value at those timestamps for each relevant time
series. It does so by taking the newest sample that is less than the lookback period ago.
The lookback period is 5 minutes by default.
The lookback period is 5 minutes by default, but can be
[set with the `--query.lookback-delta` flag](../command-line/prometheus.md)
If a target scrape or rule evaluation no longer returns a sample for a time
series that was previously present, this time series will be marked as stale.