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promql/vector_matching

This check will try to find queries that try to match vectors but have different sets of labels on both side of the query.

Consider these two time series:

http_errors{job="node-exporter", cluster="prod", instance="server1"}

and

cluster:http_errors{job="node-exporter", cluster="prod"}

One of them tracks specific instance and one aggregates series for the whole cluster. Because they have different set of labels if we want to calculate some value using both of them, for example:

http_errors / cluster:http_errors

we wouldn't get any results. To fix that we need ignore extra labels:

http_errors / ignoring(instance) cluster:http_errors

This check aims to find all queries that using vector matching where both sides of the query have different sets of labels causing no results to be returned.

NOTE: it's impossible for this check to inspect all time series in Prometheus against all other series as it would be too expensive. It will first check if given query returns anything, and only if it doesn't it will run extra checks. When running extra checks it will sample only a few time series from each side of the query, so it might not find all possible issues.

Configuration

This check doesn't have any configuration options.

How to enable it

This check is enabled by default for all configured Prometheus servers.

Example:

prometheus "prod" {
  uri     = "https://prometheus-prod.example.com"
  timeout = "60s"
  include = [
    "rules/prod/.*",
    "rules/common/.*",
  ]
}

prometheus "dev" {
  uri     = "https://prometheus-dev.example.com"
  timeout = "30s"
  include = [
    "rules/dev/.*",
    "rules/common/.*",
  ]
}

How to disable it

You can disable this check globally by adding this config block:

checks {
  disabled = ["promql/vector_matching"]
}

You can also disable it for all rules inside given file by adding a comment anywhere in that file. Example:

# pint file/disable promql/vector_matching

Or you can disable it per rule by adding a comment to it. Example:

# pint disable promql/vector_matching

If you want to disable only individual instances of this check you can add a more specific comment.

# pint disable promql/vector_matching($prometheus)

Where $prometheus is the name of Prometheus server to disable.

Example:

# pint disable promql/vector_matching(prod)

How to snooze it

You can disable this check until given time by adding a comment to it. Example:

# pint snooze $TIMESTAMP promql/vector_matching

Where $TIMESTAMP is either use RFC3339 formatted or YYYY-MM-DD. Adding this comment will disable promql/vector_matching until $TIMESTAMP, after that check will be re-enabled.