Fjall Round-Robin Database

Store timeseries data in a round-robin data structure, with customized insertion logic.

Collection Logic

Metrics are intercepted by logic that can decide whether to insert the metric, decide to transform the metric before insertion, decide the rollup logic for different tiers, etc.

Supported Languages

The following language integrations are supported:

• WebAssembly Components (feature: wasm)
• Rune (feature: rune)

The WebAssembly interface is documented in the wit files. Currently, the Rune integration is undocumented.

Screenshots

Data Layout

Supports inserting into a single circular buffer or inserting into "tiers" of data. This allows you to do simple insertions after processing some type of metric, or it allows you to consolidate your data into lower tiers. One use of this is to implement a data retention policy that decreases the precision of data over time.

Stability

The format of the data SHALL remain stable across and within versions. Any changes to the format SHALL be accompanied by automated migrations upon opening the database.

That said, changes to Fjall's storage format do not apply to this stable format guarantee.

Additions to the language interfaces will not result in a major version upgrade so long as those additions do not break existing interfaces. A breakage to existing interfaces or deprecation of a language interface will result in a major version bump.

Changes to the existing public API (e.g. the DataCell type) will result in a major version bump, so long as those changes are not backward compatible.

These version semantics will hold for versions including and following v0.1.0.

Work in Progress

This project is a work-in-progress. The interface needs some work and there's some logic missing.

• Finish implementing a complete WebAssembly interface.
• Finish implementing a complete Rune interface.
• Implement logic to ensure a stable data format, or implement migration logic to ensure stability.
• Implement logic to create backups of timeseries data.
• Create examples in Rune and Rust/WebAssembly.
• Implement tests for the format and language integrations.