PMM-7 Add PostgreSQL 18 support with new metrics and collectors

Introduce support for PostgreSQL 18, adding enhanced metrics for checkpointer, vacuum/analyze timings, and parallel worker activity. Implement new collectors for `pg_stat_io` and `pg_backend_memory_contexts` with version-specific queries, along with comprehensive tests. Update README and CI to reflect PostgreSQL 18 compatibility.

Author: BupycHuk

CHANGELOG.md

@@ -1,3 +1,14 @@
+## [Unreleased]
+
+* [ENHANCEMENT] Add PostgreSQL 18 support:
+  * Add parallel worker activity metrics (`pg_stat_database_parallel_workers_to_launch`, `pg_stat_database_parallel_workers_launched`)
+  * Add vacuum/analyze timing metrics (`pg_stat_user_tables_total_vacuum_time`, `pg_stat_user_tables_total_autovacuum_time`, `pg_stat_user_tables_total_analyze_time`, `pg_stat_user_tables_total_autoanalyze_time`)
+  * Add enhanced checkpointer metrics (`pg_stat_bgwriter_checkpoints_done_total`, `pg_stat_bgwriter_slru_written_total`)
+  * Add `pg_stat_io` collector with byte statistics and WAL I/O activity tracking
+  * Add `pg_backend_stats` collector for per-backend I/O and WAL statistics
+  * Add enhanced `pg_backend_memory_contexts` collector with type and path columns
+* [ENHANCEMENT] Update CI tested PostgreSQL versions to include PostgreSQL 18
+
 ## 0.15.0 / 2023-10-27
 
 * [ENHANCEMENT] Add 1kB and 2kB units #915

README.md

@@ -7,7 +7,7 @@
 
 Prometheus exporter for PostgreSQL server metrics.
 
-CI Tested PostgreSQL versions: `11`, `12`, `13`, `14`, `15`, `16`
+CI Tested PostgreSQL versions: `11`, `12`, `13`, `14`, `15`, `16`, `18`
 
 ## Quick Start
 This package is available for Docker:

collector/pg_backend_memory_contexts.go

@@ -0,0 +1,216 @@
+// Copyright 2024 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"
+
+	"github.com/blang/semver/v4"
+	"github.com/go-kit/log"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+const backendMemoryContextsSubsystem = "backend_memory_contexts"
+
+func init() {
+	registerCollector(backendMemoryContextsSubsystem, defaultDisabled, NewPGBackendMemoryContextsCollector)
+}
+
+type PGBackendMemoryContextsCollector struct {
+	log log.Logger
+}
+
+func NewPGBackendMemoryContextsCollector(config collectorConfig) (Collector, error) {
+	return &PGBackendMemoryContextsCollector{log: config.logger}, nil
+}
+
+var (
+	backendMemoryContextsTotalBytes = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, backendMemoryContextsSubsystem, "total_bytes"),
+		"Total bytes allocated for memory context",
+		[]string{"pid", "name", "ident", "parent", "level", "type", "path"},
+		prometheus.Labels{},
+	)
+	backendMemoryContextsUsedBytes = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, backendMemoryContextsSubsystem, "used_bytes"),
+		"Used bytes in memory context",
+		[]string{"pid", "name", "ident", "parent", "level", "type", "path"},
+		prometheus.Labels{},
+	)
+	backendMemoryContextsFreeBytes = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, backendMemoryContextsSubsystem, "free_bytes"),
+		"Free bytes in memory context",
+		[]string{"pid", "name", "ident", "parent", "level", "type", "path"},
+		prometheus.Labels{},
+	)
+	backendMemoryContextsFreeChunks = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, backendMemoryContextsSubsystem, "free_chunks"),
+		"Number of free chunks in memory context",
+		[]string{"pid", "name", "ident", "parent", "level", "type", "path"},
+		prometheus.Labels{},
+	)
+
+	// PostgreSQL 18+ query with type and path columns
+	backendMemoryContextsQuery18Plus = `
+		SELECT
+			pid,
+			name,
+			COALESCE(ident, '') as ident,
+			COALESCE(parent, '') as parent,
+			level,
+			total_bytes,
+			total_nblocks,
+			free_bytes,
+			free_chunks,
+			used_bytes,
+			type,
+			path
+		FROM pg_backend_memory_contexts
+		ORDER BY pid, name
+	`
+
+	// Pre-PostgreSQL 18 query without type and path columns
+	backendMemoryContextsQueryPre18 = `
+		SELECT
+			pid,
+			name,
+			COALESCE(ident, '') as ident,
+			COALESCE(parent, '') as parent,
+			level,
+			total_bytes,
+			total_nblocks,
+			free_bytes,
+			free_chunks,
+			used_bytes,
+			'' as type,
+			'' as path
+		FROM pg_backend_memory_contexts
+		ORDER BY pid, name
+	`
+)
+
+func (c *PGBackendMemoryContextsCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
+	// pg_backend_memory_contexts was introduced in PostgreSQL 14
+	if instance.version.LT(semver.Version{Major: 14}) {
+		return nil
+	}
+
+	db := instance.getDB()
+
+	// Use version-specific query for PostgreSQL 18+
+	query := backendMemoryContextsQueryPre18
+	if instance.version.GTE(semver.Version{Major: 18}) {
+		query = backendMemoryContextsQuery18Plus
+	}
+
+	rows, err := db.QueryContext(ctx, query)
+	if err != nil {
+		return err
+	}
+	defer rows.Close()
+
+	for rows.Next() {
+		var pid, name, ident, parent, contextType, path sql.NullString
+		var level, totalNblocks, freeChunks sql.NullInt64
+		var totalBytes, freeBytes, usedBytes sql.NullFloat64
+
+		err := rows.Scan(
+			&pid,
+			&name,
+			&ident,
+			&parent,
+			&level,
+			&totalBytes,
+			&totalNblocks,
+			&freeBytes,
+			&freeChunks,
+			&usedBytes,
+			&contextType,
+			&path,
+		)
+		if err != nil {
+			return err
+		}
+
+		pidLabel := "unknown"
+		if pid.Valid {
+			pidLabel = pid.String
+		}
+		nameLabel := "unknown"
+		if name.Valid {
+			nameLabel = name.String
+		}
+		identLabel := ""
+		if ident.Valid {
+			identLabel = ident.String
+		}
+		parentLabel := ""
+		if parent.Valid {
+			parentLabel = parent.String
+		}
+		levelLabel := "0"
+		if level.Valid {
+			levelLabel = string(rune(level.Int64 + '0'))
+		}
+		typeLabel := ""
+		if contextType.Valid {
+			typeLabel = contextType.String
+		}
+		pathLabel := ""
+		if path.Valid {
+			pathLabel = path.String
+		}
+
+		labels := []string{pidLabel, nameLabel, identLabel, parentLabel, levelLabel, typeLabel, pathLabel}
+
+		if totalBytes.Valid {
+			ch <- prometheus.MustNewConstMetric(
+				backendMemoryContextsTotalBytes,
+				prometheus.GaugeValue,
+				totalBytes.Float64,
+				labels...,
+			)
+		}
+
+		if usedBytes.Valid {
+			ch <- prometheus.MustNewConstMetric(
+				backendMemoryContextsUsedBytes,
+				prometheus.GaugeValue,
+				usedBytes.Float64,
+				labels...,
+			)
+		}
+
+		if freeBytes.Valid {
+			ch <- prometheus.MustNewConstMetric(
+				backendMemoryContextsFreeBytes,
+				prometheus.GaugeValue,
+				freeBytes.Float64,
+				labels...,
+			)
+		}
+
+		if freeChunks.Valid {
+			ch <- prometheus.MustNewConstMetric(
+				backendMemoryContextsFreeChunks,
+				prometheus.GaugeValue,
+				float64(freeChunks.Int64),
+				labels...,
+			)
+		}
+	}
+
+	return nil
+}