Percona PMM mongolog query source
Parent: Database Profiler vs Query Profiler · Published reference · snapshot 2026-10-30
↓ Facts as markdownall context files
Source-anchored research for Percona PMM mongolog query source. Run status: COMPLETED.
These notes link each claim to its source. Some citations identify archived research reports that are no longer hosted on this site. A published reference means the content is available; it does not certify independent review or accuracy.Read the editorial policy and follow the sources before relying on a claim.
How it works
- Both PMM setup and Operator documentation warn that moving or renaming active log files can interrupt mongolog collection. Validate rotation behavior when diagnosing missing QAN data. (high confidence) [source]
- Interpret Percona’s identical-analytics wording as feature/data comparability, not guaranteed identical operation coverage. This inference follows because level-2 profiling captures all operations, whereas normal diagnostic logging follows a threshold and sample rate; filters can further change selection. (high confidence) [source]
Problems, failure modes and limitations
- Mongolog can run with profiling mode off. Do not infer identical operation coverage: level-2 profiling records all operations, whereas slow-log collection follows configured logging selection. (high confidence) [source]
- PMM documents mongolog support for mongos; MongoDB cannot enable its database profiler on mongos, although diagnostic slow-operation logging remains available. (high confidence) [source]
- Mongolog requires file-based slow-operation logging, MongoDB write access to its log file, PMM Agent read access, and appropriate database privileges. (low confidence) [source]
- A June 2, 2026 user report on PMM Server/Client 3.7.1 describes getCmdLineOpts failing during slow WiredTiger recovery, followed by STARTING → STOPPING → DONE without retry. This is an unconfirmed version-specific report, not proof of a current defect. (low confidence) (verified as of 2026-06-02) [source]
- Datadog independently documents collecting MongoDB slow operations from system.profile when profiling is enabled, or via getLog when disabled. Its warning about a 1,024-event getLog buffer belongs to that API-based collector and must not be assigned to PMM’s file-tailing mongolog source. (medium confidence) (verified as of 2026-10-30) [source]
- Log collection can run with operationProfiling.mode: off and a configured slowOpThresholdMs. MongoDB must write to a file and PMM Agent must be able to read it. Disabling system.profile collection does not disable diagnostic slow-operation logging. (high confidence) [source]
Comparisons and alternatives
- Percona attributes reduced connection contention to reading files instead of querying databases for QAN. This scopes the benefit to query collection; it does not establish that all PMM components need zero connections or that logging has zero server cost. (high confidence) [source]
Facts and statements
- PMM mongolog reads MongoDB diagnostic log files for QAN; the profiler source instead reads per-database system.profile collections. An analytics interface therefore need not depend on enabling the database profiler. (high confidence) [source]
- Select log collection with pmm-admin add mongodb --query-source=mongolog. The command reference lists profiler as the default, with mongolog and none as alternatives. (high confidence) (verified as of 2026-10-30) [source]
- Official release notes introduce mongolog in PMM 3.3.0, released July 9, 2025; a forum reply naming 3.2.0 conflicts with that primary release record. (medium confidence) (verified as of 2025-07-09) [source]
- Mongolog avoids continuous profiler polling, but still connects at startup to discover the log path; its documented privileges include clusterMonitor or getCmdLineOpts. (high confidence) [source]
- Operator issue 2363 reports open /data/db/mongod.log: no such file or directory with PMM3 on Operator 1.21.2, and working mongolog collection after 1.22.0 mounted the data PVC. Treat this as reporter-tested evidence, not a universal upgrade guarantee. (low confidence) (verified as of 2026-05-28) [source]
- Percona's July 23, 2026 Operator 1.23.0 announcement lists choosing mongolog as a QAN source under K8SPSMDB-1546. (low confidence) (verified as of 2026-07-23) [source]
- PMM distinguishes stored QAN for completed queries from real-time analytics for running operations. Selecting mongolog changes the stored-query input source; it does not itself provide an in-flight operation view. (high confidence) [source]
- PMM 3.3.0, released July 9, 2025, introduced mongolog as an alternative query source intended to reduce monitoring connection pressure in deployments with many databases. (high confidence) (verified as of 2025-07-09) [source]
- Operator 1.23.1 documentation says mongolog support was added in Operator 1.23.0, requires PMM 3.3.0 or newer, and needs logcollector enabled so PMM can read logs under /data/db/logs/; select it with spec.pmm.querySource: mongolog. (low confidence) (verified as of 2026-07-10) [source]
Children
- No children recorded.