0.2.79 - Slow api fixes

server/internal/store/store.go

@@ -294,8 +294,39 @@ type Store struct {
 	pool *pgxpool.Pool
 }
 
+// defaultMaxConns is the floor on the connection pool.
+//
+// pgxpool's own default is max(4, GOMAXPROCS), which on the NAS this runs on is four —
+// and four is fewer than one household's televisions. Every one of them polls
+// /v1/status every ten seconds, and that poll alone reads the feature policy, the
+// notification preferences, the preference revision, the theme and the request
+// allowlist. Queries that each take a millisecond then queue behind each other for
+// hundreds, and the waiting is invisible: the query time is honest and the request is
+// slow anyway. A deployment that has stated pool_max_conns for itself keeps its own
+// answer — this replaces a default nobody chose, not a decision somebody made.
+const defaultMaxConns = 16
+
+// minConns keeps a few connections open. Establishing one costs a TCP connection, TLS
+// where it is configured and Postgres' own backend fork, which is several milliseconds
+// paid by whichever request happened to arrive after an idle period — most often the
+// first thing somebody does after switching a television on.
+const minConns = 4
+
 func Open(ctx context.Context, databaseURL string) (*Store, error) {
-	pool, err := pgxpool.New(ctx, databaseURL)
+	config, err := pgxpool.ParseConfig(databaseURL)
+	if err != nil {
+		return nil, fmt.Errorf("store: parse database url: %w", err)
+	}
+	if !strings.Contains(databaseURL, "pool_max_conns") && config.MaxConns < defaultMaxConns {
+		config.MaxConns = defaultMaxConns
+	}
+	if !strings.Contains(databaseURL, "pool_min_conns") && config.MinConns < minConns {
+		config.MinConns = minConns
+	}
+	// Every query in the gateway passes through here, which is what makes a slow request
+	// able to say how much of itself was Postgres.
+	config.ConnConfig.Tracer = queryTracer{}
+	pool, err := pgxpool.NewWithConfig(ctx, config)
 	if err != nil {
 		return nil, fmt.Errorf("store: connect: %w", err)
 	}