spacejn

Pure Rust journald reader with trace geometry navigation and grammar-based log folding.

spacejn reads systemd journal files directly (no journalctl dependency), with ripgrep-level performance optimizations: jemalloc, SIMD field lookup via memchr, memory-mapped file access, and O(k) reverse iteration for "last N" queries.

Usage

spacejn babel 50              # Last 50 lines of babel service
spacejn babel 30m             # Last 30 minutes
spacejn babel 5..15           # Lines 5-15 (range-addressable)
spacejn babel 14:30..15:00    # Time range (today)
spacejn babel -f              # Follow mode
spacejn ls                    # List available services
spacejn --errors              # Errors only

Features

• Direct journal parsing — reads .journal files via mmap, no subprocess overhead
• Range addressing — line ranges, duration ranges, time ranges
• Follow mode — live tail with inotify-based file watching
• Grammar-based folding — Sequitur-derived algorithm detects repeated log patterns and collapses them into named rules, showing structure instead of noise
• VTR collapse — optional integration with vtr for vertical time-wise record visualization
• Multi-file directory reading — handles rotated journal files transparently
• Colorized output — field-aware colorization with configurable palette

Install

cargo install --git https://github.com/holo-q/spacejn

Build from source

git clone https://github.com/holo-q/spacejn
cd spacejn
cargo build --release

Sibling dependencies

The vtr feature (enabled by default) expects the vtr crate cloned alongside:

git clone https://github.com/holo-q/vtr ../vtr

To build without VTR: cargo build --release --no-default-features

Architecture

src/
  cli/          Command-line interface, argument parsing, rendering pipeline
  format/       Journal binary format parser (header, entries, objects, compression)
  reader/       Multi-file journal reader with filtering, cursors, and file watching
  folding/      Grammar induction engine (Sequitur + clustering + periodicity detection)
  render/       Output renderers (terminal, JSON, grammar visualization, manifold)
  sample.rs     Sampling abstraction for journal entries
  events.rs     Structured event extraction from journal fields
  time.rs       Timestamp utilities

License

MIT