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// Copyright 2022 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"
"log/slog"
"slices"
"github.com/prometheus/client_golang/prometheus"
)
const databaseSubsystem = "database"
func init() {
registerCollector(databaseSubsystem, defaultEnabled, NewPGDatabaseCollector)
}
type PGDatabaseCollector struct {
log *slog.Logger
excludedDatabases []string
}
func NewPGDatabaseCollector(config collectorConfig) (Collector, error) {
exclude := config.excludeDatabases
if exclude == nil {
exclude = []string{}
}
return &PGDatabaseCollector{
log: config.logger,
excludedDatabases: exclude,
}, nil
}
var (
pgDatabaseSizeDesc = prometheus.NewDesc(
prometheus.BuildFQName(
namespace,
databaseSubsystem,
"size_bytes",
),
"Disk space used by the database",
[]string{"datname"}, nil,
)
pgDatabaseConnectionLimitsDesc = prometheus.NewDesc(
prometheus.BuildFQName(
namespace,
databaseSubsystem,
"connection_limit",
),
"Connection limit set for the database",
[]string{"datname"}, nil,
)
pgDatabaseQuery = "SELECT pg_database.datname, pg_database.datconnlimit FROM pg_database;"
pgDatabaseSizeQuery = "SELECT pg_database_size($1)"
)
// Update implements Collector and exposes database size and connection limits.
// It is called by the Prometheus registry when collecting metrics.
// The list of databases is retrieved from pg_database and filtered
// by the excludeDatabase config parameter. The tradeoff here is that
// we have to query the list of databases and then query the size of
// each database individually. This is because we can't filter the
// list of databases in the query because the list of excluded
// databases is dynamic.
func (c PGDatabaseCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
db := instance.getDB()
// Query the list of databases
rows, err := db.QueryContext(ctx,
pgDatabaseQuery,
)
if err != nil {
return err
}
defer rows.Close()
var databases []string
for rows.Next() {
var datname sql.NullString
var connLimit sql.NullInt64
if err := rows.Scan(&datname, &connLimit); err != nil {
return err
}
if !datname.Valid {
continue
}
database := datname.String
// Ignore excluded databases
// Filtering is done here instead of in the query to avoid
// a complicated NOT IN query with a variable number of parameters
if slices.Contains(c.excludedDatabases, database) {
continue
}
databases = append(databases, database)
connLimitMetric := 0.0
if connLimit.Valid {
connLimitMetric = float64(connLimit.Int64)
}
ch <- prometheus.MustNewConstMetric(
pgDatabaseConnectionLimitsDesc,
prometheus.GaugeValue, connLimitMetric, database,
)
}
// Query the size of the databases
for _, datname := range databases {
var size sql.NullFloat64
err = db.QueryRowContext(ctx, pgDatabaseSizeQuery, datname).Scan(&size)
if err != nil {
return err
}
sizeMetric := 0.0
if size.Valid {
sizeMetric = size.Float64
}
ch <- prometheus.MustNewConstMetric(
pgDatabaseSizeDesc,
prometheus.GaugeValue, sizeMetric, datname,
)
}
return rows.Err()
}
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