A bitemporal time series database. Corrections, restatements and out-of-order arrivals are first class: every append is an immutable layer, the newest layer wins at query time, and old values are never overwritten. Compaction collapses layers into a canonical form with every query result preserved exactly — an invariant checked by property-based tests and deterministic simulation testing on every build.
The engine is a syscall-routing microkernel (libtau): embed it in a Rust process, or run the standalone TCP server with the tauctl interactive client — same engine either way. Queries use TauQL, a small line-oriented query language.
Full documentation, tutorial, and TauQL reference: tau.bxrne.com
# Release binaries (Linux x86_64)
curl -fsSL https://github.com/bxrne/tau/releases/latest/download/tau-x86_64-linux -o tau
chmod +x tau && sudo mv tau /usr/local/bin/
curl -fsSL https://github.com/bxrne/tau/releases/latest/download/tauctl-x86_64-linux -o tauctl
chmod +x tauctl && sudo mv tauctl /usr/local/bin/
# From source / Docker
cargo install --git https://github.com/bxrne/tau tau tauctl
docker run -p 7070:7070 ghcr.io/bxrne/tau:latest
tau # in-memory server on 127.0.0.1:7070, no config needed
tauctl # interactive clientτ connect demo 127.0.0.1:7070
τ CREATE DATABASE sensors
τ CREATE LENS temperature float
τ APPEND LENS temperature 0 3600 18.5
τ AT LENS temperature 1800
VAL f18.5
τ APPEND LENS temperature 0 3600 20.0 # correction: new layer over same range
τ AT LENS temperature 1800
VAL f20 # newest layer wins; prior value preserved
τ DERIVE LENS fahrenheit AS temperature * 1.8 + 32 # lazy, recomputed per query
τ XDERIVE LENS fahrenheit_mat AS temperature * 1.8 + 32 # materialised, auto-refreshes
Casing carries meaning: TauQL keywords are UPPERCASE (CREATE, APPEND, AT, …); tauctl meta-commands are lowercase (connect, use, load). So use switches the client connection, USE switches the server database.
The server takes a TOML config (tau --config my.toml) covering the storage backend, WAL, TLS, auth, metrics, and limits; a production example lives at container/tau-config.toml and the Docker stack reads secrets (like the optional TAU_ENCRYPTION_KEY for AES-256-GCM at-rest encryption) from .env. See the tutorial, TauQL reference, and configuration docs.
cargo fmt --check
cargo clippy --all-targets --all-features -- -D warnings
cargo nextest run --release
cargo run --release --bin dst -- --seed 42The workspace layout and per-crate details are in crates/README.md; architecture rationale is in how it works. Licensed under Apache 2.0.