Monitoring & Metrics

Eka CI exposes Prometheus metrics and structured logs. Together they cover build queue health, cache utilization, GitHub integration, and rebuild detection.

Prometheus metrics

Metrics are served at /metrics on the address configured in [web]. Common series:

Metric	Type	Description
`eka_ci_build_queue_depth`	gauge	Pending builds per platform queue.
`eka_ci_build_duration_seconds`	histogram	End-to-end build wall time.
`eka_ci_build_outcome_total`	counter	Builds by outcome (`success`, `failed`, `cancelled`).
`eka_ci_graph_cache_hits_total`	counter	LRU cache hits for the dependency graph.
`eka_ci_graph_cache_misses_total`	counter	LRU cache misses.
`eka_ci_graph_cache_size`	gauge	Current number of nodes in the LRU cache.
`eka_ci_webhook_processing_seconds`	histogram	Webhook handler latency.
`eka_ci_rebuild_count`	histogram	Rebuilds detected per PR.
`eka_ci_change_summary_render_seconds`	histogram	Change-summary render time.

For deeper guidance on the cache metrics specifically, see LRU Cache Tuning.

Useful queries

# Build queue depth, per platform
eka_ci_build_queue_depth

# Cache hit rate over 5 minutes
rate(eka_ci_graph_cache_hits_total[5m])
  / (rate(eka_ci_graph_cache_hits_total[5m])
     + rate(eka_ci_graph_cache_misses_total[5m]))

# 95th percentile webhook latency
histogram_quantile(0.95,
  rate(eka_ci_webhook_processing_seconds_bucket[5m]))

Logging

Logs are emitted via the tracing crate as structured records. Verbosity is controlled through RUST_LOG:

# Set a global level
RUST_LOG=info eka-ci-server

# Per-module filters
RUST_LOG=eka_ci_server::scheduler=debug,eka_ci_server=info eka-ci-server

When run under systemd, view logs with:

journalctl -u eka-ci -f

Key log targets:

eka_ci_server::scheduler — build scheduling and queue transitions.
eka_ci_server::webhooks — incoming GitHub events.
eka_ci_server::graph — dependency graph and LRU cache activity.
eka_ci_server::change_summary — change-summary pipeline.
eka_ci_server::cache_push — cache push results and post-build hooks.

Recommended alerts

A starting set of alerts for production:

eka_ci_build_queue_depth is high for too long — pending work is not draining.
Webhook 5xx rate non-zero — GitHub deliveries are being rejected.
Cache hit rate < 0.6 sustained — LRU is undersized; see LRU Cache Tuning.
Change-summary check stuck pending > 10 minutes — see Change Summaries.

The runbook pages for the LRU cache and change-summary pipeline include more specific threshold and remediation guidance.