serverStatus bucketCatalog and collStats timeseries counters
Parent: Bucket catalog memory and closure reasons · Published reference · snapshot 2026-10-23 · skill mongodb-cohort-2d50f9ab0851
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Source-anchored research for serverStatus bucketCatalog and collStats timeseries counters. Run status: COMPLETED.
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How it works
- MongoDB documents `serverStatus.bucketCatalog` as instance-level time-series metrics. `$collStats` exposes `storageStats.timeseries` only when the `storageStats` option is specified; the manual’s time-series example uses `storageStats: {}` for the default scale, and the option also permits `storageStats: { scale: <number> }`. For a sharded collection, `$collStats` returns one document per shard, so interpret the outputs at their own scopes. (high confidence) (verified as of 2026-10-23) [source]
Comparisons and alternatives
- MongoDB defines `numBucketsClosedDueToMemoryThreshold` as closures when active buckets exceed the allowed bucket catalog cache size; `numBucketsClosedDueToCachePressure` counts closures when a bucket exceeds a dynamic size limit derived from storage-engine cache availability and `numBuckets`, which differs from the maximum bucket size limit. (high confidence) (verified as of 2026-10-20) [source]
Facts and statements
- The `bucketCatalog` documentation distinguishes state measures such as `numBuckets`, `numOpenBuckets`, `numIdleBuckets`, and `memoryUsage` from event counts such as `numBucketInserts`, `numBucketUpdates`, `numCommits`, `numWaits`, and `numMeasurementsCommitted`. (high confidence) (verified as of 2026-10-20) [source]
- `numBucketInserts` counts new buckets and `numBucketUpdates` counts updates to existing buckets; MongoDB's design README says the first committed write batch inserts a bucket and later batches update it. (high confidence) (verified as of 2026-10-20) [source]
- MongoDB describes the `$collStats` time-series fields as internal diagnostic data; the collection-level document includes bucket counters that overlap with `serverStatus.bucketCatalog` but uses a different schema. (high confidence) (verified as of 2026-10-20) [source]
- A July 16, 2026 report by Sangki Han shows `numBuckets` at 9,033 and `numBucketsClosedDueToMemoryThreshold` at 3,459,670 during an in-progress backfill. In a later completed 4,896,000-document run, after the author changed the memory threshold and bucket granularity, the report records that closure counter at zero. These are observations from one workload. (medium confidence) (verified as of 2026-10-23) [source]
- Percona's `mongodb_exporter` reference lists a `collstats` collector for `$collStats` and a collection-selection flag, but it does not document whether that collector exports nested `storageStats.timeseries` bucket fields. (low confidence) (verified as of 2026-10-20) [source]
- MongoDB's SERVER-57287 issue records a historical result-shape bug in the legacy `collStats` command on `mongos`: time-series statistics appeared only inside per-shard `shards` output, and MongoDB marked the issue fixed in 5.0.0-rc3 and 5.1.0-rc0. (low confidence) [source]
Children
- No children recorded.