Export pg_stat_archiver metrics

These are useful for knowing if WAL archiving is working successfully.

Author: russss

cmd/postgres_exporter/postgres_exporter.go

@@ -285,6 +285,19 @@ var builtinMetricMaps = map[string]intermediateMetricMap{
 true,
 0,
 },
+"pg_stat_archiver": {
+map[string]ColumnMapping{
+"archived_count": {COUNTER, "Number of WAL files that have been successfully archived", nil, nil},
+"last_archived_wal": {DISCARD, "Name of the last WAL file successfully archived", nil, nil},
+"last_archived_time": {DISCARD, "Time of the last successful archive operation", nil, nil},
+"failed_count": {COUNTER, "Number of failed attempts for archiving WAL files", nil, nil},
+"last_failed_wal": {DISCARD, "Name of the WAL file of the last failed archival operation", nil, nil},
+"last_failed_time": {DISCARD, "Time of the last failed archival operation", nil, nil},
+"stats_reset": {DISCARD, "Time at which these statistics were last reset", nil, nil},
+"last_archive_age": {GAUGE, "Time in seconds since last WAL segment was successfully archived", nil, nil},
+},
+0,
+},
 "pg_stat_activity": {
 map[string]ColumnMapping{
 "datname": {LABEL, "Name of this database", nil, nil},
@@ -363,6 +376,17 @@ var queryOverrides = map[string][]OverrideQuery{
 },
 },
 
+"pg_stat_archiver": {
+{
+semver.MustParseRange(">=0.0.0"),
+`
+SELECT *,
+extract(epoch from now() - last_archived_time) AS last_archive_age
+FROM pg_stat_archiver
+`,
+},
+},
+
 "pg_stat_activity": {
 // This query only works
 {