2 posts tagged with "prometheus"

Introduction​

The Prometheus monitoring tool can store its metrics either locally or remotely. You can configure a remote data store using the remote_write configuration. This article describes the various data store options available as well as how to set up a remote store.

Overview of Remote Storage​

By default, Prometheus stores data locally wherever it is installed. The data directory can be configured by using the --storage.tsdb.path command line option when starting Prometheus. In practice you can use a separate disk for higher performance attached to the machine where Prometheus is running.

However, this may not be possible or optimal in all situations as you might want a data store that is more suited for time series data, and has larger storage capabilities for higher data retention. Prometheus would usually run in a standalone VM or a Kubernetes pod or a Docker container, and it would not have access to such data stores by default.

A remote store can add these capabilities to Prometheus. The remote storage option can be set by using the remote_write key in the Prometheus configuration YAML file.

Introduction​

Service discovery (SD) is a mechanism by which the Prometheus monitoring tool can discover monitorable targets automatically. Instead of listing down each and every target to be scraped in the Prometheus configuration, service discovery acts as a source of targets that Prometheus can query at runtime.

Service discovery becomes crucial when there are dynamically changing hosts, especially in microservices architectures and environments like Kubernetes. In Prometheus parlance, service discovery is a way of discovering "scrape targets".

For example, pods are created dynamically in Kubernetes as a result of new services being deployed and undeployed, autoscaling events, and errors causing pods to crash and go away. If you are using Prometheus for scraping pods in such an environment, Prometheus has to know which pods are running and scrapable at any given point in time. The Kubernetes service discovery pluging enables this. Similarly, there are SD plugins for other common environments.

You can use service discovery in Prometheus with the predefined plugins, or write your own custom ones using file or HTTP, depending on the situation.