DOCS·ENGINE·METRICS
05 · ENGINE

Metrics

GET /v1/metrics returns Prometheus text format. Every metric below is emitted unconditionally and has per-index labels where it makes sense.

Counters

docs_indexedTotal docs written.
queries_executedTotal queries served.
bytes_writtenBytes to segment + WAL.
bytes_readBytes read back from segments.
rerank_requestsSearches that carried a rerank block, by outcome: applied, degraded, refused (nothing sent), failed.
rerank_documents_judgedDocuments the rerank provider returned a verdict for — the billing unit.
rerank_provider_tokensTokens the rerank provider reported, by kind: input, output.

Histograms

query_latencyFull query path, in seconds.
index_latencyMemtable + WAL write path.
flush_durationMemtable → segment flush.
merge_durationSegment merge time.
wal_write_latencyWAL fsync latency.

Gauges

segment_countLive segments per index.
doc_countVisible docs per index.
memory_usageRSS in bytes.
active_searchesIn-flight queries.
wal_size_bytesLive WAL size.

Scrape config

# prometheus.yml
scrape_configs:
  - job_name: xerj
    metrics_path: /v1/metrics
    static_configs:
      - targets: ["xerj.internal:8080"]
    authorization:
      type: Bearer
      credentials: ${XERJ_API_KEY}

Source · engine/crates/xerj-common/src/metrics.rs