broad-announce/internal/postgres/postgres.go

// Package postgres wraps pgx for the few queries the services need.
// M0 doesn't use Postgres; M1 needs it for routing + delivery.
//
// We use the pgxpool connection pool so concurrent queries don't
// step on each other.
package postgres

import (
	"context"
	"fmt"
	"time"

	"github.com/jackc/pgx/v5/pgxpool"
)

// Pool is a thin alias for *pgxpool.Pool so the call sites don't
// import pgx directly.
type Pool = pgxpool.Pool

// Connect dials Postgres with retries. The first migration run will
// hit this before the DB is up, so we wait.
func Connect(ctx context.Context, dsn string) (*Pool, error) {
	cfg, err := pgxpool.ParseConfig(dsn)
	if err != nil {
		return nil, fmt.Errorf("parse dsn: %w", err)
	}
	cfg.MaxConns = 20
	cfg.MinConns = 2
	cfg.MaxConnIdleTime = 5 * time.Minute

	var pool *Pool
	deadline, hasDeadline := ctx.Deadline()
	if !hasDeadline {
		deadline = time.Now().Add(30 * time.Second)
	}
	for {
		pool, err = pgxpool.NewWithConfig(ctx, cfg)
		if err == nil {
			pingCtx, cancel := context.WithTimeout(ctx, 3*time.Second)
			err = pool.Ping(pingCtx)
			cancel()
			if err == nil {
				return pool, nil
			}
			pool.Close()
		}
		if time.Now().After(deadline) {
			return nil, fmt.Errorf("postgres connect timeout: %w", err)
		}
		select {
		case <-ctx.Done():
			return nil, ctx.Err()
		case <-time.After(1 * time.Second):
		}
	}
}