add pg_stat_wal collector

Signed-off-by: Harry Cho <[email protected]>

collector/pg_stat_wal.go

@@ -0,0 +1,240 @@
+// Copyright 2023 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package collector
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"log/slog"
+	"strings"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+const statWALSubsystem = "stat_wal"
+
+func init() {
+	registerCollector(statWALSubsystem, defaultDisabled, NewPGStatWALCollector)
+}
+
+type PGStatWALCollector struct {
+	log *slog.Logger
+}
+
+func NewPGStatWALCollector(config collectorConfig) (Collector, error) {
+	return &PGStatWALCollector{log: config.logger}, nil
+}
+
+var statsWALRecordsDesc = prometheus.NewDesc(
+	prometheus.BuildFQName(namespace, statWALSubsystem, "wal_records"),
+	"Total number of WAL records generated",
+	[]string{},
+	prometheus.Labels{},
+)
+
+var statsWALFPIDesc = prometheus.NewDesc(
+	prometheus.BuildFQName(namespace, statWALSubsystem, "wal_fpi"),
+	"Total number of WAL full page images generated",
+	[]string{},
+	prometheus.Labels{},
+)
+
+var statsWALBytesDesc = prometheus.NewDesc(
+	prometheus.BuildFQName(namespace, statWALSubsystem, "wal_bytes"),
+	"Total amount of WAL generated in bytes",
+	[]string{},
+	prometheus.Labels{},
+)
+
+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{},
+)
+
+var statsWALWriteDesc = prometheus.NewDesc(
+	prometheus.BuildFQName(namespace, statWALSubsystem, "wal_write"),
+	"Number of times WAL buffers were written out to disk via XLogWrite request. See Section 30.5 for more information about the internal WAL function XLogWrite.",
+	[]string{},
+	prometheus.Labels{},
+)
+
+var statsWALSyncDesc = prometheus.NewDesc(
+	prometheus.BuildFQName(namespace, statWALSubsystem, "wal_sync"),
+	"Number of times WAL files were synced to disk via issue_xlog_fsync request (if fsync is on and wal_sync_method is either fdatasync, fsync or fsync_writethrough, otherwise zero). See Section 30.5 for more information about the internal WAL function issue_xlog_fsync.",
+	[]string{},
+	prometheus.Labels{},
+)
+
+var statsWALWriteTimeDesc = prometheus.NewDesc(
+	prometheus.BuildFQName(namespace, statWALSubsystem, "wal_write_time"),
+	"Total amount of time spent writing WAL buffers to disk via XLogWrite request, in milliseconds (if track_wal_io_timing is enabled, otherwise zero). This includes the sync time when wal_sync_method is either open_datasync or open_sync.",
+	[]string{},
+	prometheus.Labels{},
+)
+
+var statsWALSyncTimeDesc = prometheus.NewDesc(
+	prometheus.BuildFQName(namespace, statWALSubsystem, "wal_sync_time"),
+	"Total amount of time spent syncing WAL files to disk via issue_xlog_fsync request, in milliseconds (if track_wal_io_timing is enabled, fsync is on, and wal_sync_method is either fdatasync, fsync or fsync_writethrough, otherwise zero).",
+	[]string{},
+	prometheus.Labels{},
+)
+
+var statsWALStatsResetDesc = prometheus.NewDesc(
+	prometheus.BuildFQName(namespace, statWALSubsystem, "stats_reset"),
+	"Time at which these statistics were last reset",
+	[]string{},
+	prometheus.Labels{},
+)
+
+func statWALQuery(columns []string) string {
+	return fmt.Sprintf("SELECT %s FROM pg_stat_wal;", strings.Join(columns, ","))
+}
+
+func (c *PGStatWALCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
+	db := instance.getDB()
+
+	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
+	}
+
+	rows, err := db.QueryContext(ctx,
+		statWALQuery(columns),
+	)
+	if err != nil {
+		return err
+	}
+	defer rows.Close()
+
+	for rows.Next() {
+		var walRecords, walFPI, walBytes, walBuffersFull, walWrite, walSync sql.NullInt64
+		var walWriteTime, walSyncTime sql.NullFloat64
+		var statsReset sql.NullTime
+
+		err := rows.Scan(
+			&walRecords,
+			&walFPI,
+			&walBytes,
+			&walBuffersFull,
+			&walWrite,
+			&walSync,
+			&walWriteTime,
+			&walSyncTime,
+			&statsReset,
+		)
+		if err != nil {
+			return err
+		}
+
+		walRecordsMetric := 0.0
+		if walRecords.Valid {
+			walRecordsMetric = float64(walRecords.Int64)
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statsWALRecordsDesc,
+			prometheus.CounterValue,
+			walRecordsMetric,
+		)
+
+		walFPIMetric := 0.0
+		if walFPI.Valid {
+			walFPIMetric = float64(walFPI.Int64)
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statsWALFPIDesc,
+			prometheus.CounterValue,
+			walFPIMetric,
+		)
+
+		walBytesMetric := 0.0
+		if walBytes.Valid {
+			walBytesMetric = float64(walBytes.Int64)
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statsWALBytesDesc,
+			prometheus.CounterValue,
+			walBytesMetric,
+		)
+
+		walBuffersFullMetric := 0.0
+		if walBuffersFull.Valid {
+			walBuffersFullMetric = float64(walBuffersFull.Int64)
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statsWALBuffersFullDesc,
+			prometheus.CounterValue,
+			walBuffersFullMetric,
+		)
+
+		walWriteMetric := 0.0
+		if walWrite.Valid {
+			walWriteMetric = float64(walWrite.Int64)
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statsWALWriteDesc,
+			prometheus.CounterValue,
+			walWriteMetric,
+		)
+
+		walSyncMetric := 0.0
+		if walSync.Valid {
+			walSyncMetric = float64(walSync.Int64)
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statsWALSyncDesc,
+			prometheus.CounterValue,
+			walSyncMetric,
+		)
+
+		walWriteTimeMetric := 0.0
+		if walWriteTime.Valid {
+			walWriteTimeMetric = float64(walWriteTime.Float64)
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statsWALWriteTimeDesc,
+			prometheus.CounterValue,
+			walWriteTimeMetric,
+		)
+
+		walSyncTimeMetric := 0.0
+		if walSyncTime.Valid {
+			walSyncTimeMetric = float64(walSyncTime.Float64)
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statsWALSyncTimeDesc,
+			prometheus.CounterValue,
+			walSyncTimeMetric,
+		)
+
+		resetMetric := 0.0
+		if statsReset.Valid {
+			resetMetric = float64(statsReset.Time.Unix())
+		}
+		ch <- prometheus.MustNewConstMetric(
+			statsWALStatsResetDesc,
+			prometheus.CounterValue,
+			resetMetric,
+		)
+	}
+	return nil
+}

collector/pg_stat_wal_test.go

@@ -0,0 +1,132 @@
+package collector
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/DATA-DOG/go-sqlmock"
+	"github.com/prometheus/client_golang/prometheus"
+	dto "github.com/prometheus/client_model/go"
+	"github.com/smartystreets/goconvey/convey"
+)
+
+func TestPGStatWALCollector(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("Error opening a stub db connection: %s", err)
+	}
+	defer db.Close()
+
+	inst := &instance{db: db}
+
+	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
+	}
+
+	srT, err := time.Parse("2006-01-02 15:04:05.00000-07", "2023-05-25 17:10:42.81132-07")
+	if err != nil {
+		t.Fatalf("Error parsing time: %s", err)
+	}
+
+	rows := sqlmock.NewRows(columns).
+		AddRow(354, 4945, 289097744, 1242257, int(3275602074), 89320867, 450.123439, 1234.5678, srT)
+	mock.ExpectQuery(sanitizeQuery(statWALQuery(columns))).WillReturnRows(rows)
+
+	ch := make(chan prometheus.Metric)
+	go func() {
+		defer close(ch)
+		c := PGStatWALCollector{}
+
+		if err := c.Update(context.Background(), inst, ch); err != nil {
+			t.Errorf("Error calling PGStatWALCollector.Update: %s", err)
+		}
+	}()
+
+	expected := []MetricResult{
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 354},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 4945},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 289097744},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 1242257},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 3275602074},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 89320867},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 450.123439},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 1234.5678},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 1685059842},
+	}
+
+	convey.Convey("Metrics comparison", t, func() {
+		for _, expect := range expected {
+			m := readMetric(<-ch)
+			convey.So(expect, convey.ShouldResemble, m)
+		}
+	})
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("there were unfulfilled exceptions: %s", err)
+	}
+}
+
+func TestPGStatWALCollectorNullValues(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("Error opening a stub db connection: %s", err)
+	}
+	defer db.Close()
+
+	inst := &instance{db: db}
+	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
+	}
+
+	rows := sqlmock.NewRows(columns).
+		AddRow(nil, nil, nil, nil, nil, nil, nil, nil, nil)
+	mock.ExpectQuery(sanitizeQuery(statWALQuery(columns))).WillReturnRows(rows)
+
+	ch := make(chan prometheus.Metric)
+	go func() {
+		defer close(ch)
+		c := PGStatWALCollector{}
+
+		if err := c.Update(context.Background(), inst, ch); err != nil {
+			t.Errorf("Error calling PGStatWALCollector.Update: %s", err)
+		}
+	}()
+
+	expected := []MetricResult{
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 0},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 0},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 0},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 0},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 0},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 0},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 0},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 0},
+		{labels: labelMap{}, metricType: dto.MetricType_COUNTER, value: 0},
+	}
+
+	convey.Convey("Metrics comparison", t, func() {
+		for _, expect := range expected {
+			m := readMetric(<-ch)
+			convey.So(expect, convey.ShouldResemble, m)
+		}
+	})
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("there were unfulfilled exceptions: %s", err)
+	}
+}