Introduction to Prometheus

What is Prometheus?

Prometheus is an open-source systems monitoring and alerting toolkit originally built at SoundCloud. Since its inception in 2012, many companies and organizations have adopted Prometheus, and the project has a very active developer and user community. It is now a standalone open source project and maintained independently of any company. To emphasize this, and to clarify the project’s governance structure, Prometheus joined the Cloud Native Computing Foundation in 2016 as the second hosted project, after Kubernetes.

— prometheus.io

Prometheus doesn’t use protocols such as SMNP or some sort of agent service. Instead, it pulls (scrapes) metrics from a client (target) over http and places the data into its local time series database that you can query using its own DSL.

Prometheus uses exporters that are installed and configured on the clients in order to convert and expose their metrics in a Prometheus format. The Prometheus server then scrapes the exporter for metrics.

By default Prometheus comes with a UI that can be accessed on port 9090 on the Prometheus server. Users also have the ability to build dashboards and integrate their favorite visualization software, such as Grafana.

Prometheus uses a separate component for alerting called the AlertManager. The AlertManager receives metrics from the Prometheus server and then is responsible for grouping and making sense of the metrics and then forwarding an alert to your chosen notification system. The AlertManager currently supports email, Slack, VictorOps, HipChat, WebHooks and many more.

Important terms :

Prometheus Server :

The main server that scrapes and stores the scraped metrics in a time series DB.

Scrape :

Prometheus server uses a pulling method to retrieve metrics.

Target :

The Prometheus servers clients that it retrieves info from.

Exporter :

Target libraries that convert and export existing metrics into Prometheus format.

Alert Manager :

Component responsible for handling alerts.

Prometheus Architecture.

Prometheus Architecture

Prometheus scrapes metrics from exports, stores them in the TSDB on the Prometheus server and then pushes alerts to Alertmanager.

The Service discovery component is a feature that allows Prometheus to auto discover different targets since these targets will come and go so frequently in a distributed system or microservice orchestration style of architecture. We will not be responsible for continuously updating a static list of target addresses each time a service and/or a piece of infrastructure is removed or added. Prometheus will automatically discover and start/stop scraping for us.