Add a collector for stat_wal#1167
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Docs: https://www.postgresql.org/docs/current/monitoring-stats.html#MONITORING-PG-STAT-WAL-VIEW We use this collector in production and have done so for some time. Signed-off-by: Peter Nuttall <peter.nuttall@snowflake.com>
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sysadmind
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May 13, 2026
| db := instance.getDB() | ||
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| columns := []string{ | ||
| "wal_records", // bigint |
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I think this list was probably valid for 17, but it looks like they took some away in 18. https://www.postgresql.org/docs/18/monitoring-stats.html#MONITORING-PG-STAT-WAL-VIEW
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Pull request overview
Adds a new Prometheus collector for PostgreSQL’s pg_stat_wal view, extending the exporter’s built-in monitoring coverage for WAL generation and I/O timing.
Changes:
- Introduces
PGStatWALCollectorto scrapepg_stat_walfields and export them as Prometheus metrics. - Adds unit tests using
sqlmockto validate metric emission for populated and NULL-valued rows.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.
| File | Description |
|---|---|
| collector/pg_stat_wal.go | New collector implementation querying pg_stat_wal and exporting WAL-related metrics. |
| collector/pg_stat_wal_test.go | Tests for the new collector, including normal and NULL-value scenarios. |
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| defer rows.Close() | ||
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| for rows.Next() { | ||
| var walRecords, walFPI, walBytes, walBuffersFull, walWrite, walSync sql.NullInt64 |
| prometheus.CounterValue, | ||
| resetMetric, | ||
| ) | ||
| } |
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| func (c *PGStatWALCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error { | ||
| db := instance.getDB() | ||
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| columns := []string{ | ||
| "wal_records", // bigint | ||
| "wal_fpi", // bigint | ||
| "wal_bytes", // numeric | ||
| "wal_buffers_full", // bigint | ||
| "wal_write", // bigint | ||
| "wal_sync", // bigint | ||
| "wal_write_time", // double precision | ||
| "wal_sync_time", // double precision | ||
| "stats_reset", // timestamp with time zone | ||
| } | ||
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| rows, err := db.QueryContext(ctx, | ||
| statWALQuery(columns), | ||
| ) | ||
| if err != nil { | ||
| return err | ||
| } |
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| prometheus.BuildFQName(namespace, statWALSubsystem, "wal_fpi"), | ||
| "Total number of WAL full page images generated", | ||
| []string{}, | ||
| prometheus.Labels{}, | ||
| ) | ||
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| var statsWALBytesDesc = prometheus.NewDesc( | ||
| prometheus.BuildFQName(namespace, statWALSubsystem, "wal_bytes"), | ||
| "Total amount of WAL generated in bytes", | ||
| []string{}, | ||
| prometheus.Labels{}, | ||
| ) | ||
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| var statsWALBuffersFullDesc = prometheus.NewDesc( | ||
| prometheus.BuildFQName(namespace, statWALSubsystem, "wal_buffers_full"), | ||
| "Number of times WAL data was written to disk because WAL buffers became full", | ||
| []string{}, | ||
| prometheus.Labels{}, | ||
| ) | ||
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| var statsWALWriteDesc = prometheus.NewDesc( | ||
| prometheus.BuildFQName(namespace, statWALSubsystem, "wal_write"), |
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Docs: https://www.postgresql.org/docs/current/monitoring-stats.html#MONITORING-PG-STAT-WAL-VIEW
We use this collector in production and have done so for some time.