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Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallPrometheus evaluates an alerting rule and sends active alert information to Alertmanager. Alertmanager then matches the alert against its routing tree, groups it with related alerts when configured, checks whether it should be silenced or inhibited, and dispatches a notification through the selected receiver. This is a conceptual walkthrough of the documented lifecycle, not a trace captured from a particular deployment.
1. Prometheus evaluates the alerting rule
The journey begins with a Prometheus alerting rule. Its expression identifies a condition; any configured timing conditions determine when the rule becomes active. Prometheus evaluates rules and sends alert information to Alertmanager, potentially updating Alertmanager about alert states periodically. Prometheus describes alerting rules as identifying what is broken now, while Alertmanager takes over notification management. See the alerting rules documentation and the alerting overview.
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This separation matters when diagnosing a missing page: first establish whether the rule is firing in Prometheus, then follow the alert into Alertmanager. Alertmanager cannot notify about an alert that Prometheus has not sent.
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2. Alertmanager matches the alert to a route
Every alert enters the configured top-level route, which must match all alerts. Alertmanager evaluates child routes using their matchers and configuration. A matching child route with continue: false stops evaluation of sibling routes; with continue: true, later siblings may also be considered. If no child route matches, the alert is handled at the current route. Child routes inherit optional settings from their parent unless they override them.
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In practice, check the alert’s labels against the route matchers, then account for route order and the continue setting. Matcher syntax and available fields can vary by Alertmanager version; the current configuration reference notes UTF-8 matcher parser changes for version 0.27 and later, so verify examples against the version actually deployed. See Alertmanager configuration.
3. Grouping and timing shape notification delivery
Routing determines where an alert is handled; grouping determines which alerts can be presented together. A route’s group_by labels define the grouping key. Alertmanager may therefore send one notification containing several similar alerts rather than a separate message for each alert.
The route timing settings influence when that message is sent or repeated. The configuration reference documents defaults of 30 seconds for group_wait, 5 minutes for group_interval, and 4 hours for repeat_interval. These are defaults, not universal recommendations. A longer initial group_wait gives related alerts or an inhibiting alert time to arrive, but delays the first notification. If an alert resolves before that wait expires, Alertmanager does not send a notification for it.
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4. Silences and inhibition can suppress a notification
Before treating a missing notification as a routing failure, check Alertmanager’s suppression mechanisms:
- Silence: mutes alerts matching its configured criteria for a specified period.
- Inhibition: suppresses a target alert when a matching source alert exists and the configured equality labels agree.
These mechanisms do not mean the underlying alert never existed. They affect notification handling. The Alertmanager concepts documentation and configuration reference describe grouping, silencing, inhibition, and routing.
5. A receiver turns the route decision into a message
A route selects a named receiver. The receiver configuration identifies one or more notification integrations, such as email, Slack, or a webhook. A webhook can also connect Alertmanager to a notification mechanism without a native integration.
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Notification templates determine how the message is presented. Available data includes the receiver name, notification status, alerts, group labels, common labels and annotations, route labels, and an Alertmanager backlink. A template can show information shared by the group or iterate over individual alerts. The exact destination and message depend on the route, receiver configuration, and template in that deployment.
Consult the notification template reference and the list of notification integrations.
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Tracing the path in a real deployment
Alertmanager’s configuration reference documents distributed tracing controls, including an HTTP or gRPC client type, endpoint, sampling fraction, TLS or insecure behavior, custom HTTP headers, compression, and timeout. Those settings describe how tracing may be configured; they do not establish that tracing is enabled, that a trace was sampled, or that a particular span represents a particular alert. To make deployment-specific claims, verify the installed Alertmanager version and its active configuration. See the tracing configuration reference.
Alertmanager also documents an optional event recorder, gated by the event-recorder feature flag. It can record process start and shutdown, alert lifecycle transitions, silence creation, notification delivery, and mute or inhibit suppressions, then send events to configured destinations. That can provide a useful lifecycle timeline if the feature is enabled and configured; its documentation alone does not show that a deployment has recorded any events. The feature and configuration details are in the configuration reference.
High availability changes the destination path
In a high-availability setup, Prometheus should send alerts to all Alertmanager instances rather than send them through a load balancer. That distinction affects how alerts reach the Alertmanager cluster; it is separate from the later route, grouping, suppression, and receiver decisions. See the Prometheus Authors’ high-availability guidance.
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