EXPERIMENTAL: This is an experimental feature.
Experimental features are subject to frequent breaking changes, and may be removed with no equivalent replacement.
The stability.level flag must be set to experimental to use the feature.
The foreach block runs a separate pipeline for each item inside a list.
The template block contains the definition of Alloy components which will be ran for every item in the collection.
The contents of the block look like a normal Alloy configuration file,
except that you can use the keyword defined in var to refer to the current item in the collection.
Components inside the template block can use exports of components defined outside of the foreach block.
However, components outside of the foreach cannot use exports from components defined inside the template block of a foreach.
Example
The following example shows you how to run Prometheus exporters dynamically on service discovery targets.
prometheus.exporter.* components often require the address of one particular instance being monitored.
For example, prometheus.exporter.redis has a redis_addr attribute for the Redis instance under observation.
On the other hand, discovery.* components such as discovery.kubernetes output a list of targets such as this:
You can use a foreach to loop over each target and start a separate component pipeline for it.
The following example configuration shows how a prometheus.exporter.redis instance is started for each Redis instance discovered by discovery.kubernetes.
Additional Kubernetes labels from discovery.kubernetes are also added to the metrics created by prometheus.exporter.redis.
alloy
discovery.kubernetes"default"{role ="pod"}discovery.relabel"redis"{targets = discovery.kubernetes.default.targets
// Remove all targets except the Redis ones.rule{source_labels =["__meta_kubernetes_pod_container_name"]regex ="redis-cont"action ="keep"}}// Collect metrics for each Redis instance.foreach"redis"{collection = discovery.relabel.redis.output
var ="each"template{prometheus.exporter.redis"default"{// This is the "__address__" label from discovery.kubernetes.redis_addr = each["__address__"]}prometheus.scrape"default"{targets = prometheus.exporter.redis.default.targets
forward_to =[prometheus.relabel.default.receiver]}// Add labels from discovery.kubernetes.prometheus.relabel"default"{rule{replacement = each["__meta_kubernetes_namespace"]target_label ="k8s_namespace"action ="replace"}rule{replacement = each["__meta_kubernetes_pod_container_name"]target_label ="k8s_pod_container_name"action ="replace"}forward_to =[prometheus.remote_write.mimir.receiver]}}}prometheus.remote_write"mimir"{endpoint{url ="https://prometheus-xxx.grafana.net/api/prom/push"basic_auth{username = sys.env("<PROMETHEUS_USERNAME>")password = sys.env("<GRAFANA_CLOUD_API_KEY>")}}}
Replace the following:
<PROMETHEUS_USERNAME>: Your Prometheus username.
<GRAFANA_CLOUD_API_KEY>: Your Grafana Cloud API key.