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.

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.

Corium Operator Manual