Cortex, an open source, horizontally scalable, multi-tenant Prometheus-as-a-service becomes a CNCF Sandbox project

• Service providers to enable them to manage a large number of Prometheus instances and provide long-term storage.
• Enterprises to centralize management of large-scale Prometheus deployments and ensure long-term durability of Prometheus data.

Originally developed by Weaveworks, it is now being used in production by organizations like Grafana Labs, FreshTracks, and EA.

How does it work?

The following diagram shows its architecture:

Source: CNCF

1. Scraping samples: First, a Prometheus instance scraps all of the users’ services and then forwards them to a Cortex deployment. It does this using the remote_write API, which was added to Prometheus to support Cortex and other integrations.

2. Distributor distributes the samples: The instance then sends all these samples to distributor, which is a stateless service that consults the ring to figure out which ingesters should ingest the sample. The ingesters are arranged using a consistent hash ring, keyed on the fingerprint of the time series, and stored in a consistent data store, such as Consul.

Distributor finds the owner ingester and forwards the sample to it and also to two ingesters after it in the ring. This means if an ingester goes down, we have two others that have its data.

3. Ingesters make chunks of samples: Ingesters continuously receive a stream of samples and group them together in chunks. These chunks are then stored in a backend database, such as DynamoDB, BigTable, or Cassandra. Ingesters facilitate this chunking process so that Cortex isn’t constantly writing to its backend database.

Alexis Richardson, CEO of Weaveworks believes that being a CNCF Sandbox project will help grow the Prometheus ecosystem:

“By joining CNCF, Cortex will have a neutral home for collaboration between contributor companies, while allowing the Prometheus ecosystem to grow a more robust set of integrations and solutions. Cortex already has a strong affinity with several CNCF technologies, including Kubernetes, gRPC, OpenTracing and Jaeger, so it’s a natural fit for us to continue building on these interoperabilities as part of CNCF.”

To know more in detail, check out the official announcement by CNCF and also read What is Cortex?, a blog post published on Weaveworks Blog.

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