Apache Cassandra® committers are working hard, building new features to help you more seamlessly ease operational challenges of a distributed database. Let’s dive into some recently approved CEPs and explain how these upcoming features will improve your workflow and efficiency.
What is a CEP?
CEP stands for Cassandra Enhancement Proposal. They are the process for outlining, discussing, and gathering endorsements for a new feature in Cassandra. They’re more than a feature request; those who put forth a CEP have intent to build the feature, and the proposal encourages a high amount of collaboration with the Cassandra contributors.
The CEPs discussed here were recently approved for implementation or have had significant progress in their implementation. As with all open-source development, inclusion in a future release is contingent upon successful implementation, community consensus, testing, and approval by project committers.
CEP-42: Constraints framework
With collaboration from NetApp Instaclustr, CEP-42, and subsequent iterations, delivers schema level constraints giving Cassandra users and operators more control over their data. Adding constraints on the schema level means that data can be validated at write time and send the appropriate error when data is invalid.
Constraints are defined in-line or as a separate definition. The inline style allows for only one constraint while a definition allows users to define multiple constraints with different expressions.
The scope of this CEP-42 initially supported a few constraints that covered the majority of cases, but in follow up efforts the expanded list of support includes scalar (>, <, >=, <=), LENGTH(), OCTET_LENGTH(), NOT NULL, JSON(), REGEX(). A user is also able to define their own constraints if they implement it and put them on Cassandra’s class path.
A simple example of an in-line constraint:
CREATE TABLE users (
username text PRIMARY KEY,
age int CHECK age >= 0 and age < 120
);
Constraints are not supported for UDTs (User-Defined Types) nor collections (except for using NOT NULL for frozen collections).
Enabling constraints closer to the data is a subtle but mighty way for operators to ensure that data goes into the database correctly. By defining rules just once, application code is simplified, more robust, and prevents validation from being bypassed. Those who have worked with MySQL, Postgres, or MongoDB will enjoy this addition to Cassandra.
CEP-51: Support “Include” Semantics for cassandra.yaml
The cassandra.yaml file holds important settings for storage, memory, replication, compaction, and more. It’s no surprise that the average size of the file around 1,000 lines (though, yes—most are comments). CEP-51 enables splitting the cassandra.yaml configuration into multiple files using includes semantics. From the outside, this feels like a small change, but the implications are huge if a user chooses to opt-in.
In general, the size of the configuration file makes it difficult to manage and coordinate changes. It’s often the case that multiple teams manage various aspects of the single file. In addition, cassandra.yaml permissions are readable for those with access to this file, meaning private information like credentials are comingled with all other settings. There is risk from an operational and security standpoint.
Enabling the new semantics and therefore modularity for the configuration file eases management, deployment, complexity around environment-specific settings, and security in one shot. The configuration file follows the principle of least privilege once the cassandra.yaml is broken up into smaller, well-defined files; sensitive configuration settings are separated out from general settings with fine-grained access for the individual files. With the feature enabled, different development teams are better equipped to deploy safely and independently.
If you’ve deployed your Cassandra cluster on the NetApp Instaclustr platform, the cassandra.yaml file is already configured and managed for you. We pride ourselves on making it easy for you to get up and running fast.
CEP-52: Schema annotations for Apache Cassandra
With extensive review by the NetApp Instaclustr team and Stefan Miklosovic, CEP-52 introduces schema annotations in CQL allowing in-line comments and labels of schema elements such as keyspaces, tables, columns, and User Defined Types (UDT). Users can easily define and alter comments and labels on these elements. They can be copied over when desired using CREATE TABLE LIKE syntax. Comments are stored as plain text while labels are stored as structured metadata.
Comments and labels serve different annotation purposes: Comments document what a schema object is for, whereas labels describe how sensitive or controlled it is meant to be. For example, labels can be used to identify columns as “PII” or “confidential”, while the comment on that column explains usage, e.g. “Last login timestamp.”
Users can query these annotations. CEP-52 defines two new read-only tables (system_views.schema_comments and system_views.schema_security_labels) to store comments and security labels so objects with comments can be returned as a list or a user/machine process can query for specific labels, beneficial for auditing and classification. Note that adding security labels are descriptive metadata and do not enforce access control to the data.
CEP-53: Cassandra rolling restarts via Sidecar
Sidecar is an auxiliary component in the Cassandra ecosystem that exposes cluster management and streaming capabilities through APIs. Introducing rolling restarts through Sidecar, this feature is designed to provide operators with more efficient and safer restarts without cluster-wide downtime. More specifically, operators can monitor, pause, resume, and abort restarts all through an API with configurable options if restarts fail.
Rolling restarts brings operators a step closer to cluster-wide operations and lifecycle management via Sidecar. Operators will be able to configure the number of nodes to restart concurrently with minimal risk as this CEP unleashes clear states as a node progresses through a restart. Accounting for a variety of edge cases, an operator can feel assured that, for example, a non-functioning sidecar won’t derail operations.
The current process for restarting a node is a multi-step, manual process, which does not scale for large cluster sizes (and is also tedious for small clusters). Restarting clusters previously lacked a streamlined approach as each node needed to be restarted one at a time, making the process time-intensive and error-prone.
Though Sidecar is still considered WIP, it’s got big plans to improve operating large clusters!
The NetApp Instaclustr Platform, in conjunction with our expert TechOps team already orchestrates these laborious tasks for our Cassandra customers with a high level of care to ensure their cluster stays online. Restarting or upgrading your Cassandra nodes is a huge pain-point for operators, but it doesn’t have to be when using our managed platform (with round-the-clock support!)
CEP-54: Zstd with dictionary SSTable compression
CEP-54, with NetApp Instaclustr’s collaboration, aims to add support Zstd with dictionary compression for SSTables. Zstd, or Zstandard, is a fast, lossless data compression algorithm that boasts impressive ratio and speed and has been supported in Cassandra since 4.0. Certain workloads can benefit from significantly faster read/write performance, reduced storage footprint, and increased storage device lifetime when using dictionary compression.
At a high level, operators choose a table they want to compress with a dictionary. A dictionary must be trained first on a small amount of already present data (recommended no more than 10MiB). The result of a training is a dictionary, which is stored cluster-wide for all other nodes to use, and this dictionary is used for all subsequent writes of SSTables to a disk.
Workloads with structured data of similar rows benefit most from Zstd with dictionary compression. Some examples of ideal workloads include event logs, telemetry data, metadata tables with templated messages. Think: repeated row data. If the table data is too unstructured or random, this feature likely won’t be optimal for dictionary compression, however plain Zstd will still be an excellent option.
New SSTables with dictionaries are readable across nodes and can stream, repair, and backup. Existing tables are unaffected if dictionary compression is not enabled. Too many unique dictionaries hurt decompression; use minimal dictionaries (recommended dictionary size is about 100KiB and one dictionary per table) and only adopt new ones when they’re noticeably better.
CEP-55: Generated role names
CEP-55 adds support to create users/roles without supplying a name, simplifying
user management, especially when generating users and roles in bulk. With an example syntax, CREATE GENERATED ROLE WITH GENERATED PASSWORD, new keys are placed in a newly introduced configuration section in cassandra.yaml under “role_name_policy.”
Stefan Miklosovic, our Cassandra engineer at NetApp Instaclustr, created this CEP as a logical follow up to CEP-24 (password validation/generation), which he authored as well. These quality-of-life improvements let operators spend less time doing trivial tasks with high-risk potential and more time on truly complex matters.
Manual name selection seems trivial until a hundred role names need to be generated; now there is a security risk if the new usernames—or worse passwords—are easily guessable. With CEP-55, the generated role name will be UUID-like, with optional prefix/suffix and size hints, however a pluggable policy is available to generate and validate names as well. This is an opt-in feature with no effect to the existing method of generating role names.
The future of Apache Cassandra is bright
These Cassandra Enhancement Proposals demonstrate a strong commitment to making Apache Cassandra more powerful, secure, and easier to operate. By staying on top of these updates, we ensure our managed platform seamlessly supports future releases that accelerate your business needs.
At NetApp Instaclustr, our expert TechOps team already orchestrates laborious tasks like restarts and upgrades for our Apache Cassandra customers, ensuring their clusters stay online. Our platform handles the complexity so you can get up and running fast.
Learn more about our fully managed and hosted Apache Cassandra offering and try it for free today!
