Long running transactions marginalia

Signed-off-by: Felix Yuan <felix.yuan@reddit.com>

collector/pg_long_running_transactions_marginalia.go

@@ -0,0 +1,94 @@
+// 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"
+
+"github.com/go-kit/log"
+"github.com/prometheus/client_golang/prometheus"
+)
+
+const longRunningTransactionsMarginaliaSubsystem = "long_running_transactions_marginalia"
+
+func init() {
+registerCollector(longRunningTransactionsMarginaliaSubsystem, defaultEnabled, NewPGLongRunningTransactionsMarginaliaCollector)
+}
+
+type PGLongRunningTransactionsMarginaliaCollector struct {
+log log.Logger
+}
+
+func NewPGLongRunningTransactionsMarginaliaCollector(config collectorConfig) (Collector, error) {
+return &PGLongRunningTransactionsMarginaliaCollector{log: config.logger}, nil
+}
+
+var (
+longRunningTransactionsMarginaliaMaxAgeInSeconds = prometheus.NewDesc(
+prometheus.BuildFQName(namespace, longRunningTransactionsMarginaliaSubsystem, "max_age_in_seconds"),
+"The current maximum transaction age in seconds",
+[]string{"application", "endpoint"},
+prometheus.Labels{},
+)
+
+longRunningTransactionsMarginaliaQuery = `
+SELECT
+activity.matches[1] AS application,
+activity.matches[2] AS endpoint,
+MAX(age_in_seconds) AS max_age_in_seconds
+FROM (
+SELECT
+regexp_matches(query, '^\s*(?:\/\*(?:application:(\w+),?)?(?:correlation_id:\w+,?)?(?:jid:\w+,?)?(?:endpoint_id:([\w/\-\.:\#\s]+),?)?.*?\*\/)?\s*(\w+)') AS matches,
+EXTRACT(EPOCH FROM (clock_timestamp() - xact_start)) AS age_in_seconds
+FROM
+pg_catalog.pg_stat_activity
+WHERE state <> 'idle'
+AND (clock_timestamp() - xact_start) > '30 seconds'::interval
+AND query NOT LIKE 'autovacuum:%'
+) activity
+GROUP BY application, endpoint
+ORDER BY max_age_in_seconds DESC
+`
+)
+
+func (PGLongRunningTransactionsMarginaliaCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
+db := instance.getDB()
+rows, err := db.QueryContext(ctx,
+longRunningTransactionsMarginaliaQuery)
+
+if err != nil {
+return err
+}
+defer rows.Close()
+
+for rows.Next() {
+var application, endpoint string
+var max_age_in_seconds float64
+
+if err := rows.Scan(&application, &endpoint, &max_age_in_seconds); err != nil {
+return err
+}
+
+ch <- prometheus.MustNewConstMetric(
+longRunningTransactionsAgeInSeconds,
+prometheus.GaugeValue,
+max_age_in_seconds,
+application, endpoint,
+)
+}
+if err := rows.Err(); err != nil {
+return err
+}
+return nil
+}

collector/pg_long_running_transactions_marginalia_test.go

@@ -0,0 +1,64 @@
+// 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"
+"testing"
+
+"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 xTestPGLongRunningTransactionsMarginaliaCollector(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{
+"application",
+"endpoint",
+"max_age_in_seconds",
+}
+rows := sqlmock.NewRows(columns).
+AddRow("reddit", "GET /r/programming", 32)
+
+// TODO: Fix the sanitizeQuery escaper to deal better with regex
+mock.ExpectQuery(sanitizeQuery(longRunningTransactionsMarginaliaQuery)).WillReturnRows(rows)
+
+ch := make(chan prometheus.Metric)
+go func() {
+defer close(ch)
+c := PGLongRunningTransactionsMarginaliaCollector{}
+
+if err := c.Update(context.Background(), inst, ch); err != nil {
+t.Errorf("Error calling PGLongRunningTransactionsMarginaliaCollector.Update: %s", err)
+}
+}()
+expected := []MetricResult{
+{labels: labelMap{}, value: 25, metricType: dto.MetricType_GAUGE},
+}
+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)
+}
+}