Add a prometheus label mapping component

CHANGELOG.md

@@ -22,6 +22,8 @@ Main (unreleased)
 
 - Add `otelcol.exporter.syslog` component to export logs in syslog format (@dehaansa)
 
+- Add a `prometheus.mapping` component to add a label based on a source_label and a mapping table. (@vaxvms)
+
 ### Enhancements
 
 - Add second metrics sample to the support bundle to provide delta information (@dehaansa)

docs/design/2025-prometheus-mapping-component.md

@@ -0,0 +1,45 @@
+# Proposal: Add a component to perform label mapping efficiently
+
+* Author(s): Nicolas DUPEUX
+* Last updated: 19/11/2024
+* Original issue: https://github.com/grafana/alloy/pull/2025
+
+## Abstract
+
+Add a component to populate a label value based on a lookup table
+
+## Problem
+
+Using `prometheus.relabel` to populate a label value based on another label value is inefficient as we have to have a rule block for each source label value.
+
+If we have 1k values to map, we'll have to execute 1k regex for each datapoint resulting in an algorithm complexity of O(n).
+
+## Proposal
+
+Replace regex computing by a lookup table. Algorithm complexity goes from O(n) to O(1)
+
+## Pros and cons
+
+Pros:
+    - resource efficient
+
+Cons:
+    - New component
+
+## Alternative solutions
+
+- Instanciate more CPU resources to perform the task
+- Optimize prometheus.relabel component
+- Summarize regex when severals keys have to same value.
+
+## Compatibility
+
+As this is a new component, there isn't any compatibility issue as long as you don't use it.
+
+## Implementation
+
+https://github.com/grafana/alloy/pull/2025
+
+## Related open issues
+
+None

docs/sources/reference/compatibility/_index.md

@@ -173,6 +173,7 @@ The following components, grouped by namespace, _export_ Prometheus `MetricsRece
 {{< /collapse >}}
 
 {{< collapse title="prometheus" >}}
+- [prometheus.mapping](../components/prometheus/prometheus.mapping)
 - [prometheus.relabel](../components/prometheus/prometheus.relabel)
 - [prometheus.remote_write](../components/prometheus/prometheus.remote_write)
 - [prometheus.write.queue](../components/prometheus/prometheus.write.queue)
@@ -192,6 +193,7 @@ The following components, grouped by namespace, _consume_ Prometheus `MetricsRec
 {{< /collapse >}}
 
 {{< collapse title="prometheus" >}}
+- [prometheus.mapping](../components/prometheus/prometheus.mapping)
 - [prometheus.operator.podmonitors](../components/prometheus/prometheus.operator.podmonitors)
 - [prometheus.operator.probes](../components/prometheus/prometheus.operator.probes)
 - [prometheus.operator.servicemonitors](../components/prometheus/prometheus.operator.servicemonitors)

docs/sources/reference/components/prometheus/prometheus.mapping.md

@@ -0,0 +1,133 @@
+---
+canonical: https://grafana.com/docs/alloy/latest/reference/components/prometheus/prometheus.mapping/
+description: Learn about prometheus.mapping
+title: prometheus.mapping
+---
+
+# prometheus.mapping
+
+Prometheus metrics follow the [OpenMetrics](https://openmetrics.io/) format.
+Each time series is uniquely identified by its metric name, plus optional
+key-value pairs called labels. Each sample represents a datapoint in the
+time series and contains a value and an optional timestamp.
+
+```text
+<metric name>{<label_1>=<label_val_1>, <label_2>=<label_val_2> ...} <value> [timestamp]
+```
+
+The `prometheus.mapping` component create new labels on each metric passed
+along to the exported receiver by applying a mapping table to a label value.
+
+The most common use of `prometheus.mapping` is to create new labels with a high
+cardinality source label value (>1k) when a large set of regex is inefficient.
+
+You can specify multiple `prometheus.mapping` components by givin them
+different labels.
+
+## Usage
+
+```alloy
+prometheus.mapping "LABEL" {
+  forward_to = RECEIVER_LIST
+
+  source_label = "labelA"
+
+  mapping = {
+    "from" = {"labelB" = "to"},
+    ...
+  }
+}
+```
+
+## Arguments
+
+The following arguments are supported:
+
+Name           | Type                      | Description                                                             | Default | Required
+---------------|---------------------------|-------------------------------------------------------------------------|---------|---------
+`forward_to`   | `list(MetricsReceiver)`   | Where the metrics should be forwarded to, after relabeling takes place. |         | yes
+`source_label` | `string`                  | Name of the source label to use for mapping.                            |         | yes
+`target_label` | `string`                  | Name of the target label to use for mapping.                            |         | yes
+`mapping`      | `map(string,map(string))` | Mapping from source label value to target labels name/value.            |         | yes
+
+## Exported fields
+
+The following fields are exported and can be referenced by other components:
+
+Name       | Type              | Description
+-----------|-------------------|-----------------------------------------------------------
+`receiver` | `MetricsReceiver` | The input receiver where samples are sent to be relabeled.
+
+## Component health
+
+`prometheus.mapping` is only reported as unhealthy if given an invalid
+configuration. In those cases, exported fields are kept at their last healthy
+values.
+
+## Debug information
+
+`prometheus.mapping` doesn't expose any component-specific debug information.
+
+## Debug metrics
+
+* `prometheus_mapping_metrics_processed` (counter): Total number of metrics processed.
+* `prometheus_mapping_metrics_written` (counter): Total number of metrics written.
+
+## Example
+
+You can create and an instance of a see `prometheus.mapping` component and see how
+it acts on the following metrics.
+
+```alloy
+prometheus.mapping "keep_backend_only" {
+  forward_to = [prometheus.remote_write.onprem.receiver]
+
+  source_label = "app"
+
+  mapping = {
+    "frontend" = {"team" = "teamA"}
+    "backend"  = {"team" = "teamB"}
+    "database" = {"team" = "teamC"}
+  }
+}
+```
+
+```
+metric_a{__address__ = "localhost", instance = "development", app = "frontend"} 10
+metric_a{__address__ = "localhost", instance = "development", app = "backend"}  2
+metric_a{__address__ = "cluster_a", instance = "production",  app = "frontend"} 7
+metric_a{__address__ = "cluster_a", instance = "production",  app = "backend"}  9
+metric_a{__address__ = "cluster_b", instance = "production",  app = "database"} 4
+```
+
+After applying the mapping a new `team` label is created based on mapping table
+and `app` label value.
+
+```
+metric_a{team = "teamA", __address__ = "localhost", instance = "development", app = "frontend"} 10
+metric_a{team = "teamB", __address__ = "localhost", instance = "development", app = "backend"}  2
+metric_a{team = "teamA",  __address__ = "cluster_a", instance = "production",  app = "frontend"} 7
+metric_a{team = "teamA",  __address__ = "cluster_a", instance = "production",  app = "backend"}  9
+metric_a{team = "teamC",  __address__ = "cluster_a", instance = "production",  app = "database"} 4
+```
+
+The resulting metrics are then propagated to each receiver defined in the
+`forward_to` argument.
+<!-- START GENERATED COMPATIBLE COMPONENTS -->
+
+## Compatible components
+
+`prometheus.mapping` can accept arguments from the following components:
+
+- Components that export [Prometheus `MetricsReceiver`](../../../compatibility/#prometheus-metricsreceiver-exporters)
+
+`prometheus.mapping` has exports that can be consumed by the following components:
+
+- Components that consume [Prometheus `MetricsReceiver`](../../../compatibility/#prometheus-metricsreceiver-consumers)
+
+{{< admonition type="note" >}}
+Connecting some components may not be sensible or components may require further configuration to make the connection work correctly.
+Refer to the linked documentation for more details.
+{{< /admonition >}}
+
+<!-- END GENERATED COMPATIBLE COMPONENTS -->

internal/component/all/all.go

@@ -132,6 +132,7 @@ import (
 	_ "github.com/grafana/alloy/internal/component/prometheus/exporter/statsd"               // Import prometheus.exporter.statsd
 	_ "github.com/grafana/alloy/internal/component/prometheus/exporter/unix"                 // Import prometheus.exporter.unix
 	_ "github.com/grafana/alloy/internal/component/prometheus/exporter/windows"              // Import prometheus.exporter.windows
+	_ "github.com/grafana/alloy/internal/component/prometheus/mapping"                       // Import prometheus.mapping
 	_ "github.com/grafana/alloy/internal/component/prometheus/operator/podmonitors"          // Import prometheus.operator.podmonitors
 	_ "github.com/grafana/alloy/internal/component/prometheus/operator/probes"               // Import prometheus.operator.probes
 	_ "github.com/grafana/alloy/internal/component/prometheus/operator/servicemonitors"      // Import prometheus.operator.servicemonitors