64 lines
1.7 KiB
Go
64 lines
1.7 KiB
Go
package postgres
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import (
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"context"
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"database/sql"
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"time"
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_ "github.com/lib/pq"
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"bugs.watch/agent/internal/aggregate"
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)
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// Collector queries PostgreSQL status each sample interval.
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// All queries run under a 3-second timeout; any failure is silently skipped.
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type Collector struct {
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db *sql.DB
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}
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func New(dsn string) (*Collector, error) {
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db, err := sql.Open("postgres", dsn)
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if err != nil {
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return nil, err
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}
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db.SetMaxOpenConns(2)
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db.SetMaxIdleConns(1)
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db.SetConnMaxLifetime(5 * time.Minute)
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return &Collector{db: db}, nil
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}
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func (c *Collector) Name() string { return "postgres" }
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func (c *Collector) Close() { c.db.Close() }
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func (c *Collector) Collect(window *aggregate.Window) {
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ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
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defer cancel()
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// pg_stat_database is readable by any user for their own database.
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var numBackends, maxConn int
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err := c.db.QueryRowContext(ctx,
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`SELECT d.numbackends, s.setting::int
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FROM pg_stat_database d, pg_settings s
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WHERE d.datname = current_database() AND s.name = 'max_connections'`,
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).Scan(&numBackends, &maxConn)
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if err == nil && maxConn > 0 {
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window.AddDBConnPct(float64(numBackends) / float64(maxConn) * 100)
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}
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// pg_stat_activity requires pg_monitor role (PG 10+); silently skip on error.
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var activeQueries int
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if err := c.db.QueryRowContext(ctx,
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`SELECT count(*) FROM pg_stat_activity WHERE state = 'active'`,
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).Scan(&activeQueries); err == nil {
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window.AddDBThreadsRunning(float64(activeQueries))
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}
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var sizeBytes int64
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if err := c.db.QueryRowContext(ctx,
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`SELECT pg_database_size(current_database())`,
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).Scan(&sizeBytes); err == nil {
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window.SetDBSizeBytes(uint64(sizeBytes))
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}
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}
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