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collector.wal: add pg_wal_lsn_location_bytes - WAL LSN bytes #1188

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collector.wal: add pg_wal_lsn_location_bytes - WAL LSN bytes #1188

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25 changes: 23 additions & 2 deletions collector/pg_wal.go
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Original file line number Diff line number Diff line change
Expand Up @@ -52,10 +52,26 @@ var (
[]string{}, nil,
)

pgWALLSNInBytes = prometheus.NewDesc(
prometheus.BuildFQName(
namespace,
walSubsystem,
"lsn_location_bytes",
),
"WAL Log Sequence Number in bytes",
[]string{}, nil,
)

pgWALQuery = `
SELECT
COUNT(*) AS segments,
SUM(size) AS size
SUM(size) AS size,
(SELECT CASE
WHEN pg_is_in_recovery() THEN
pg_wal_lsn_diff(pg_last_wal_replay_lsn(), '0/0')::int8
ELSE
pg_wal_lsn_diff(pg_current_wal_lsn(), '0/0')::int8
END) AS lsn_location_bytes
FROM pg_ls_waldir()
WHERE name ~ '^[0-9A-F]{24}$'`
)
Expand All @@ -68,7 +84,8 @@ func (c PGWALCollector) Update(ctx context.Context, instance *instance, ch chan<

var segments uint64
var size uint64
err := row.Scan(&segments, &size)
var lsnbytes uint64
err := row.Scan(&segments, &size, &lsnbytes)
if err != nil {
return err
}
Expand All @@ -80,5 +97,9 @@ func (c PGWALCollector) Update(ctx context.Context, instance *instance, ch chan<
pgWALSize,
prometheus.GaugeValue, float64(size),
)
ch <- prometheus.MustNewConstMetric(
pgWALLSNInBytes,
prometheus.GaugeValue, float64(lsnbytes),
)
return nil
}
5 changes: 3 additions & 2 deletions collector/pg_wal_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -31,9 +31,9 @@ func TestPgWALCollector(t *testing.T) {

inst := &instance{db: db}

columns := []string{"segments", "size"}
columns := []string{"segments", "size", "lsn_location_bytes"}
rows := sqlmock.NewRows(columns).
AddRow(47, 788529152)
AddRow(47, 788529152, 123456789)
mock.ExpectQuery(sanitizeQuery(pgWALQuery)).WillReturnRows(rows)

ch := make(chan prometheus.Metric)
Expand All @@ -49,6 +49,7 @@ func TestPgWALCollector(t *testing.T) {
expected := []MetricResult{
{labels: labelMap{}, value: 47, metricType: dto.MetricType_GAUGE},
{labels: labelMap{}, value: 788529152, metricType: dto.MetricType_GAUGE},
{labels: labelMap{}, value: 123456789, metricType: dto.MetricType_GAUGE},
}

convey.Convey("Metrics comparison", t, func() {
Expand Down