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/prometheus/client_golang/prometheus"
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)
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const walSubsystem = "wal"
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func init() {
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	registerCollector(walSubsystem, defaultEnabled, NewPGWALCollector)
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}
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type PGWALCollector struct {
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}
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func NewPGWALCollector(config collectorConfig) (Collector, error) {
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	return &PGWALCollector{}, nil
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}
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var (
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	pgWALSegments = prometheus.NewDesc(
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		prometheus.BuildFQName(
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			namespace,
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			walSubsystem,
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			"segments",
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		),
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		"Number of WAL segments",
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		[]string{}, nil,
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	)
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	pgWALSize = prometheus.NewDesc(
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		prometheus.BuildFQName(
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			namespace,
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			walSubsystem,
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			"size_bytes",
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		),
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		"Total size of WAL segments",
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		[]string{}, nil,
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	)
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	pgWALQuery = `
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		SELECT
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			COUNT(*) AS segments,
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			SUM(size) AS size
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		FROM pg_ls_waldir()
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		WHERE name ~ '^[0-9A-F]{24}$'`
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)
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func (c PGWALCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
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	db := instance.getDB()
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	row := db.QueryRowContext(ctx,
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		pgWALQuery,
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	)
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	var segments uint64
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	var size uint64
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	err := row.Scan(&segments, &size)
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	if err != nil {
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		return err
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	}
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	ch <- prometheus.MustNewConstMetric(
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		pgWALSegments,
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		prometheus.GaugeValue, float64(segments),
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	)
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	ch <- prometheus.MustNewConstMetric(
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		pgWALSize,
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		prometheus.GaugeValue, float64(size),
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	)
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	return nil
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}
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