Citus Blog

If you're building a software application that serves multiple tenants, you may have already encountered the challenges of managing and isolating tenant-specific data. That's where the django-multitenant library comes in. This library, actively used since 2017 and now downloaded more than 10K times per month, offers a simple and flexible solution for building multi-tenant Django applications.

In this blog post, we'll dive deeper into the concept of multi-tenancy and explore how Django-multitenant can help you build scalable, secure, and maintainable multi-tenant applications on top of PostgreSQL and the Citus database extension. We'll also provide a practical example of how to use Django-multitenant in a real-world scenario. So, if you're looking to simplify your multi-tenant development process, keep reading.

Citus enables several different PostgreSQL use cases, but one of the most popular ones is to build scalable multi-tenant software as a service (SaaS) applications. The most common way to build a multi-tenant application on Citus is to distribute all your Postgres tables by a “tenant ID” column. That way rows are (hash-)distributed across nodes, while rows with the same tenant ID value are co-located on the same node for fast local joins, transactions, and foreign keys.

For those of you who build SaaS apps, one question many of you have is how active your tenants are. More specifically: What are your busiest tenants? How many queries is your application doing on behalf of your tenants, and how much CPU do those queries use?

The new 11.3 release to the open source Citus database extension gives you tenant monitoring—with instant visibility into your top tenants using the new citus_stat_tenants feature, which shows query counts and CPU usage over a configurable time period.

Citus is a PostgreSQL extension that makes PostgreSQL scalable by transparently distributing and/or replicating tables across one or more PostgreSQL nodes. Citus could be used either on Azure cloud, or since the Citus database extension is fully open source, you can download and install Citus anywhere you like.

A typical Citus cluster consists of a special node called coordinator and a few worker nodes. Applications usually send their queries to the Citus coordinator node, which relays them to worker nodes and accumulates the results. (Unless of course you’re using the Citus query from any node feature, an optional feature introduced in Citus 11, in which case the queries can be routed to any of the nodes in the cluster.)

Anyway, one of the most frequently asked questions is: “How does Citus handle failures of the coordinator or worker nodes? What’s the HA story?”

And with the exception of when you’re running Citus in a managed service in the cloud, the answer so far was not great—just use PostgreSQL streaming to run coordinator and workers with HA and it is up to you how to handle a failover.

In this blog post, you’ll learn how Patroni 3.0+ can be used to deploy a highly available Citus database cluster—just by adding a few lines to the Patroni configuration file.

Our goal for the Citus extension is for you to be able to use all PostgreSQL features at any scale, with a seamless scaling experience. Distributed tables (or more generally “Citus tables”) are a powerful tool to get high performance at any scale. There are only a few remaining limitations when distributing a PostgreSQL table, but we are determined to solve them all. The Citus 11.2 release checks off another five SQL & DDL features that now work seamlessly on Citus tables. We also improved progress tracking for the shard rebalancer, so you know exactly what’s going on when rebalancing your cluster.

We also want PostgreSQL tools to work out-of-the-box even if you have a distributed PostgreSQL cluster. One of the most frequent questions we get on the Citus Slack from our open source users is how to set up high availability. Alexander Kukushkin, who is the primary maintainer of Patroni and recently joined the Citus database engine team, therefore developed a new version of Patroni which includes support for Citus!

Before we dive in, you can find detailed release notes for Citus 11.2 by the engineering team on our Updates page.

As you may have heard, we recently made PostgreSQL 15 generally available in Azure Cosmos DB for PostgreSQL within just 1 week of the PostgreSQL 15 release. The Postgres 15 version is available for you whether you need to create a new cluster in Azure Cosmos DB for PostgreSQL, or upgrade your existing cluster. (Note: you can do in-place major version upgrades in Azure Cosmos DB for PostgreSQL.) And the PostgreSQL 15 support is available in all Azure regions that support Azure Cosmos DB for PostgreSQL.

You may be surprised since it's usually not the norm for a managed database service to start supporting the new major PostgreSQL version that early... This post will walk you through what's going on behind the scenes that enables us to do such a feat. Some background before diving in:

Azure Cosmos DB for PostgreSQL is powered by native Postgres and Citus open source—and enables you to run PostgreSQL at any scale, from a single node to a large, distributed cluster. Customers can also scale out as much as they want depending on their needs with many additional features. The Hyperscale (Citus) managed service recently moved into Azure Cosmos DB family (more info on the launch of Azure Cosmos DB for PostgreSQL in this blog post) and with that introduced try Azure Cosmos DB for PostgreSQL for free where you can try out PostgreSQL 15 with Citus 11.1.

Big news from the Postgres and Citus team here at Microsoft! Just 1 week after PostgreSQL 15 was released, PostgreSQL 15 GA is generally available in the portal for the Azure Cosmos DB for PostgreSQL managed service—in all Azure regions. Whether you need to provision new clusters in Azure Cosmos DB for Postgres—or upgrade your existing database clusters—Postgres 15 is now a choice for you. Oh, and you can upgrade your existing cluster to Postgres 15 from any of the other supported major Postgres versions, using the in-place major version upgrade feature.

Citus is a distributed database that is built entirely as an open source PostgreSQL extension. In fact, you can install it in your PostgreSQL server without changing any PostgreSQL functionality. Citus simply gives PostgreSQL additional superpowers.

Being an extension also means we can keep adding new Postgres superpowers at a high pace. In the last release (11.0), we focused on giving you the ability to query from any node, opening up Citus for many new use cases, and we also made Citus fully open source. That means you can see everything we do on the Citus GitHub page (and star the repo if you’re a fan 😊). It also means that everyone can take advantage of shard rebalancing without write-downtime.

In the latest release (11.1), our Citus database team at Microsoft improved the application’s experience and avoided blocking writes during important operations like distributing tables and tenant isolation. These new capabilities built on the experience gained from developing the shard rebalancer, which uses logical replication to avoid blocking writes. In addition, we made the shard rebalancer faster and more user-friendly; also, we prepared for the upcoming PostgreSQL 15 release. This post gives you a quick tour of the major changes in Citus 11.1, including:

A few months ago we made Citus fully open source. This was a very exciting milestone for all of us on the Citus database engine team. Contrary to folks who say that Postgres is a monolith that can’t scale—Postgres in fact has a fully open source solution for distributed scale, one that’s also native to Postgres. It’s called Citus! This post will go into more detail on why we open sourced our few remaining enterprise features in Citus 11, what exactly we open sourced, and finally what it took to actually open source our code. If you’re more interested in the code instead, you can find it in our GitHub repo (feel free to give the Citus project a star.)

We released Citus 11 in the previous weeks and it is packed. Citus went full open source, so now previously enterprise features like the non-blocking aspect of the shard rebalancer—and multi-user support—are all open source for everyone to enjoy. One other huge change in Citus 11 is now you can query your distributed Postgres tables from any Citus node, by default.

When using Citus to distribute Postgres before Citus 11, the coordinator node was your application’s only point of contact. Your application needed to connect to the coordinator to query your distributed Postgres tables. Coordinator node can handle high query throughput, about 100K per second but your application might need even more processing power. Thanks to our work in Citus 11 you can now query from any node in the Citus database cluster you want. In Citus 11 we sync the metadata to all nodes by default, so you can connect to any node and run queries on your tables.

Running queries from any node is awesome but you also need to be able to monitor and manage your queries from any node. Before, when you only connected the coordinator, using Postgres’ monitoring tools was enough but this is not the case anymore. So in Citus 11 we added some ways to observe your queries similar to you would do in a single Postgres instance.

Citus 11.0 is here! Citus is a PostgreSQL extension that adds distributed database superpowers to PostgreSQL. With Citus, you can create tables that are transparently distributed or replicated across a cluster of PostgreSQL nodes. Citus 11.0 is a new major release, which means that it comes with some very exciting new features that enable new levels of scalability.

The biggest enhancement in Citus 11.0 is that you can now always run distributed queries from any node in the cluster because the schema & metadata are automatically synchronized. We already shared some of the details in the Citus 11.0 beta blog post, but we also have big surprise for those of you who use Citus open source that was not part of the initial beta.

When we do a new Citus release, we usually release 2 versions: The open source version and the enterprise release which includes a few extra features. However, there will be only one version of Citus 11.0, because everything in the Citus extension is now fully open source!

That means that you can now rebalance shards without blocking writes, manage roles across the cluster, isolate tenants to their own shards, and more. All this comes on top of the already massive enhancement in Citus 11.0: You can query your Citus cluster from any node, creating a truly distributed PostgreSQL experience.