Monitoring

Three surfaces report the state of a Corium system: the metrics endpoint, corium db stats, and the tracing log.

The metrics endpoint

Pass --metrics-listen to a transactor or a peer server:

corium transactor --data-dir /srv/corium --metrics-listen 127.0.0.1:9464

The endpoint serves Prometheus text at /metrics.

CAUTION: Keep the metrics listener on a private operations network. The endpoint has no bearer-token authentication.

Transactor metrics

Metric	Type	Meaning
corium_transactor_transactions_total	Counter	Committed transactions.
corium_transactor_transaction_failures_total	Counter	Rejected transactions.
corium_transactor_transaction_latency_seconds	Histogram	Commit latency.
corium_transactor_queue_depth	Gauge	Commit queue depth.
corium_transactor_index_duration_seconds	Histogram	Index publication duration.
corium_transactor_gc_runs_total	Counter	Collection runs.
corium_transactor_gc_swept_blobs_total	Counter	Blobs deleted.
corium_transactor_gc_retained_blobs_total	Counter	Unreachable blobs kept by the window.
corium_keys_unavailable	Gauge	Nodes that cannot load a key manifest change.

Peer server metrics

Metric	Type	Meaning
corium_peer_queries_total	Counter	Queries served.
corium_peer_query_latency_seconds	Histogram	Query latency.
corium_peer_query_fuel_spent_total	Counter	Datoms touched.

Segment cache metrics

A peer server with --segment-cache-dir adds these.

Metric	Labels	Meaning
corium_peer_segment_cache_requests_total	result, tier	Hits and misses per tier.
corium_peer_segment_cache_native_fetches_total	result	Fetches that went to storage.
corium_peer_segment_cache_bytes_read_total	source	Bytes read per source.
corium_peer_segment_cache_admissions_total	result	Admissions and rejections.
corium_peer_segment_cache_used_bytes	tier	Bytes in use.
corium_peer_segment_cache_capacity_bytes	tier	Configured capacity.

On-demand statistics

corium db stats people

The command prints the basis, the index basis, the index lag, the counts, and the transactor counters. See the database catalog.

The transactor Status call carries the same data. The Metrics panel of corium tui samples it live, and it is the only surface that shows lease ownership.

Auditing schema changes

Every applied schema update records its requester, its digests, its observed basis, and its acknowledgements on the transaction entity. Those are ordinary attributes, so the schema history of a database is a query.

[:find ?when ?who ?tool
 :where [?tx :db.schemaUpdate/requester ?who]
        [?tx :db.schemaUpdate/tool ?tool]
        [?tx :db/txInstant ?when]]

[[#inst 1785899778642 "static-token:operator" "corium-cli/0.1.0"]]

The requester is the authenticated principal. A caller never supplies it.

An ordinary transaction cannot write :db.schemaUpdate/*, so no transaction can claim to have been a schema update. See schema management.

Logging

Tracing is human-readable by default. --log-format json writes structured logs, and RUST_LOG filters them.

RUST_LOG=corium_transactor=info,corium_peer=warn \
  corium --log-format json transactor --data-dir /srv/corium

--log-format is a global flag, so it comes before the subcommand.

Useful targets:

Target	Content
corium_transactor	Commit pipeline, indexing, leases, garbage collection.
corium_peer	Connection, subscription, failover.
corium_authz::audit	Every authorization decision, with its basis. Denials at info, grants at debug.

Log lines worth an alert:

• standby took over write lease — a failover happened.
• deposed — this member lost the lease. It stands down on its own.
• standing by; lease held elsewhere — normal on a standby at startup.

What to alert on

Signal	Condition	Meaning
Index lag	Grows without limit	Publication cannot keep up.
corium_transactor_queue_depth	Stays high	The write path is saturated.
corium_transactor_transaction_failures_total	Rises sharply	Validation errors, or a fenced writer.
corium_keys_unavailable	Above zero	A node cannot load a key manifest change.
corium_transactor_gc_retained_blobs_total	Grows steadily	Storage is not being reclaimed.
Lease owner	Changes unexpectedly	An unplanned failover.

Peer memory is not exported as a metric. Watch the resident memory of the process, because a peer holds the whole history. See indexes and storage.