pangolin_exporter

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// Copyright 2023 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package collector
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import (
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	"context"
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	"github.com/go-kit/log"
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	"github.com/prometheus/client_golang/prometheus"
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)
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const longRunningTransactionsSubsystem = "long_running_transactions"
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func init() {
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	registerCollector(longRunningTransactionsSubsystem, defaultDisabled, NewPGLongRunningTransactionsCollector)
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}
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type PGLongRunningTransactionsCollector struct {
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	log log.Logger
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}
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func NewPGLongRunningTransactionsCollector(config collectorConfig) (Collector, error) {
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	return &PGLongRunningTransactionsCollector{log: config.logger}, nil
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}
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var (
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	longRunningTransactionsCount = prometheus.NewDesc(
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		"pg_long_running_transactions",
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		"Current number of long running transactions",
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		[]string{},
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		prometheus.Labels{},
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	)
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	longRunningTransactionsAgeInSeconds = prometheus.NewDesc(
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		prometheus.BuildFQName(namespace, longRunningTransactionsSubsystem, "oldest_timestamp_seconds"),
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		"The current maximum transaction age in seconds",
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		[]string{},
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		prometheus.Labels{},
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	)
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	longRunningTransactionsQuery = `
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	SELECT
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		COUNT(*) as transactions,
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   		MAX(EXTRACT(EPOCH FROM clock_timestamp())) AS oldest_timestamp_seconds
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    FROM pg_catalog.pg_stat_activity
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    WHERE state is distinct from 'idle' AND query not like 'autovacuum:%'
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	`
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)
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func (PGLongRunningTransactionsCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
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	db := instance.getDB()
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	rows, err := db.QueryContext(ctx,
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		longRunningTransactionsQuery)
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	if err != nil {
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		return err
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	}
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	defer rows.Close()
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	for rows.Next() {
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		var transactions, ageInSeconds float64
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		if err := rows.Scan(&transactions, &ageInSeconds); err != nil {
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			return err
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		}
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		ch <- prometheus.MustNewConstMetric(
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			longRunningTransactionsCount,
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			prometheus.GaugeValue,
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			transactions,
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		)
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		ch <- prometheus.MustNewConstMetric(
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			longRunningTransactionsAgeInSeconds,
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			prometheus.GaugeValue,
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			ageInSeconds,
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		)
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	}
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	if err := rows.Err(); err != nil {
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		return err
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	}
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	return nil
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}
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