Add collector for database/sql#DBStats

MaxIdleTimeClosed is not available below go1.15.
Therefore it is TODO.

Signed-off-by: Mitsuo Heijo <[email protected]>

Author: johejo

prometheus/dbstats_collector.go

@@ -0,0 +1,123 @@
+// Copyright 2021 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 prometheus
+
+import "database/sql"
+
+type dbStatsCollector struct {
+	db *sql.DB
+
+	maxOpenConnections *Desc
+
+	openConnections  *Desc
+	inUseConnections *Desc
+	idleConnections  *Desc
+
+	waitCount     *Desc
+	waitDuration  *Desc
+	maxIdleClosed *Desc
+	// maxIdleTimeClosed *Desc // TODO: for 1.15 or later
+	maxLifetimeClosed *Desc
+}
+
+// DBStatsCollectorOpts defines the behavior of a db stats collector
+// created with NewDBStatsCollector.
+type DBStatsCollectorOpts struct {
+	// DriverName holds the name of driver.
+	// It will not used for empty strings.
+	DriverName string
+}
+
+// NewDBStatsCollector returns a collector that exports metrics about the given *sql.DB.
+// See https://golang.org/pkg/database/sql/#DBStats for more information on stats.
+func NewDBStatsCollector(db *sql.DB, opts DBStatsCollectorOpts) Collector {
+	var fqName func(name string) string
+	if opts.DriverName == "" {
+		fqName = func(name string) string {
+			return "go_db_stats_" + name
+		}
+	} else {
+		fqName = func(name string) string {
+			return "go_" + opts.DriverName + "_db_stats_" + name
+		}
+	}
+	return &dbStatsCollector{
+		db: db,
+		maxOpenConnections: NewDesc(
+			fqName("max_open_connections"),
+			"Maximum number of open connections to the database.",
+			nil, nil,
+		),
+		openConnections: NewDesc(
+			fqName("open_connections"),
+			"The number of established connections both in use and idle.",
+			nil, nil,
+		),
+		inUseConnections: NewDesc(
+			fqName("in_use_connections"),
+			"The number of connections currently in use.",
+			nil, nil,
+		),
+		idleConnections: NewDesc(
+			fqName("idle_connections"),
+			"The number of idle connections.",
+			nil, nil,
+		),
+		waitCount: NewDesc(
+			fqName("wait_count_total"),
+			"The total number of connections waited for.",
+			nil, nil,
+		),
+		waitDuration: NewDesc(
+			fqName("wait_duration_seconds_total"),
+			"The total time blocked waiting for a new connection.",
+			nil, nil,
+		),
+		maxIdleClosed: NewDesc(
+			fqName("max_idle_closed_total"),
+			"The total number of connections closed due to SetMaxIdleConns.",
+			nil, nil,
+		),
+		maxLifetimeClosed: NewDesc(
+			fqName("max_lifetime_closed_toal"),
+			"The total number of connections closed due to SetConnMaxLifetime.",
+			nil, nil,
+		),
+	}
+}
+
+// Describe implements Collector.
+func (c *dbStatsCollector) Describe(ch chan<- *Desc) {
+	ch <- c.maxOpenConnections
+	ch <- c.openConnections
+	ch <- c.inUseConnections
+	ch <- c.idleConnections
+	ch <- c.waitCount
+	ch <- c.waitDuration
+	ch <- c.maxIdleClosed
+	ch <- c.maxLifetimeClosed
+}
+
+// Collect implements Collector.
+func (c *dbStatsCollector) Collect(ch chan<- Metric) {
+	stats := c.db.Stats()
+	ch <- MustNewConstMetric(c.maxOpenConnections, GaugeValue, float64(stats.MaxOpenConnections))
+	ch <- MustNewConstMetric(c.openConnections, GaugeValue, float64(stats.OpenConnections))
+	ch <- MustNewConstMetric(c.inUseConnections, GaugeValue, float64(stats.InUse))
+	ch <- MustNewConstMetric(c.idleConnections, GaugeValue, float64(stats.Idle))
+	ch <- MustNewConstMetric(c.waitCount, CounterValue, float64(stats.WaitCount))
+	ch <- MustNewConstMetric(c.waitDuration, CounterValue, stats.WaitDuration.Seconds())
+	ch <- MustNewConstMetric(c.maxIdleClosed, CounterValue, float64(stats.MaxIdleClosed))
+	ch <- MustNewConstMetric(c.maxLifetimeClosed, CounterValue, float64(stats.MaxLifetimeClosed))
+}

prometheus/dbstats_collector_test.go

@@ -0,0 +1,64 @@
+// Copyright 2021 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 prometheus
+
+import (
+	"database/sql"
+	"testing"
+)
+
+func TestDBStatsCollector(t *testing.T) {
+	reg := NewRegistry()
+	db := new(sql.DB)
+	opts := DBStatsCollectorOpts{DriverName: "test"}
+	if err := reg.Register(NewDBStatsCollector(db, opts)); err != nil {
+		t.Fatal(err)
+	}
+
+	mfs, err := reg.Gather()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	names := []string{
+		"go_test_db_stats_max_open_connections",
+		"go_test_db_stats_open_connections",
+		"go_test_db_stats_in_use",
+		"go_test_db_stats_idle",
+		"go_test_db_stats_wait_duration",
+		"go_test_db_stats_max_idle_closed",
+		"go_test_db_stats_max_lifetime_closed",
+	}
+	type result struct {
+		found bool
+	}
+	results := make(map[string]result)
+	for _, name := range names {
+		results[name] = result{found: false}
+	}
+	for _, mf := range mfs {
+		for _, name := range names {
+			if name == mf.GetName() {
+				results[name] = result{found: true}
+				break
+			}
+		}
+	}
+
+	for name, result := range results {
+		if !result.found {
+			t.Errorf("%s not found", name)
+		}
+	}
+}