Project post by Prometheus maintainers

Prometheus, the leading open source monitoring solution hosted by CNCF, has announced today a new operating mode: the Prometheus Agent. This new way of working enables new workflows such as low-resources environments, edge networks, and IoT. It uses significantly fewer resources and is able to efficiently forward data to centralized remote endpoints, all while using the stable code base millions of Prometheus users rely upon.

Prometheus Agent is a specialized mode that focuses on three parts that have made the success of Prometheus: service discovery, scraping, and remote writing. Built into Prometheus itself, Prometheus Agent behaves like a normal Prometheus server: it is a pull-based mechanism, scraping metrics over HTTP and replicating the data to remote write endpoints. 

Over the years, the Prometheus server has been used in many different situations. From traditional servers to huge cloud-native clusters. The default mode of data forwarding in Prometheus is federation. While this is reliable, it does not match all users’ operational needs. Prometheus introduced Prometheus Remote Write, allowing for other solutions to aggregate into a global view. Of particular note are the CNCF sister projects Cortex and Thanos.

Still, Prometheus itself remains a component in such setups, scraping and forwarding metrics. Our users have been successfully using Prometheus in decentralized scenarios that report all or some of their metrics to remote write endpoints. This works reliably and at scale, but at a cost: full Prometheus servers still have many capabilities not required for forwarding, in particular full local storage.

In this new mode, the data is not available to query locally. Instead, it can be forwarded to Prometheus or any other compliant remote write endpoints.

“Our agent removes the data immediately after successful writes”, says Bartek Plotka, Principal Software Engineer at Red Hat. “This enables Prometheus Agent to use only a fraction of resources Prometheus would normally use in a similar situation. It is also a drop-in replacement for Prometheus server mode, as the behavior, interfaces, and configuration are the same.”

It is worth noting that the new persistent buffering mechanism, called Write-Ahead-Log (WAL) was heavily inspired by the existing Prometheus TSDB WAL. It was implemented initially in Grafana Agent in 2020 and has been successfully battle-tested since then on numerous deployments. Thanks to Robert Fratto, Grafana Agent Tech Lead at Grafana Labs, for the initial implementation and upstreaming the implementation to our main Prometheus repository and binary for native use and upstream maintenance.

The Prometheus Agent is available in beta right now. Read more on the Prometheus blog.