fix(db): attach an error handler to the pg pool (#3172)

A Postgres connection can drop at any time — e.g. a serverless Postgres such as
Neon terminating the connection (error code 57P01). node-postgres surfaces this as
an 'error' event; without a listener node re-throws it as an unhandled 'error' and
crashes the process. Idle clients emit on the pool, but a client that is connecting
or checked out emits on the client itself, so we listen on both the pool and each
client. The pool then discards the dead client and opens a fresh one on the next
query, so the server survives transient/idle disconnects.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

packages/db/src/client.ts

@@ -11,7 +11,21 @@ declare global {
 
 export function getPool() {
 	if (!globalThis.__pool) {
-		globalThis.__pool = new Pool({ connectionString: env.DATABASE_URL });
+		const pool = new Pool({ connectionString: env.DATABASE_URL });
+		const logPgError = (error: unknown) => {
+			console.error("[db] postgres connection error:", error);
+		};
+		// A Postgres connection can drop at any time — e.g. a serverless Postgres such as Neon
+		// terminating the connection (code 57P01). `pg` surfaces this as an 'error' event, and
+		// without a listener node re-throws it as an unhandled 'error' that crashes the process.
+		// Idle clients emit on the pool; a client that is connecting or checked out emits on the
+		// client itself, so we must listen on both. The pool then discards the dead client and
+		// opens a fresh one on the next query.
+		pool.on("error", logPgError);
+		pool.on("connect", (client) => {
+			client.on("error", logPgError);
+		});
+		globalThis.__pool = pool;
 	}
 	return globalThis.__pool;
 }