From 623dcd97dc832f3dd2e3d23cae1869ea74b1548f Mon Sep 17 00:00:00 2001
From: Hugo Dutka <hugo@coder.com>
Date: Thu, 5 Jun 2025 15:54:13 +0200
Subject: [PATCH] fix(cli): fix flakes related to context cancellation when
 establishing pg connections (#18246)

Since https://github.com/coder/coder/pull/18195 was merged, we started
running CLI tests with postgres instead of just dbmem. This surfaced
errors related to context cancellation while establishing postgres
connections.

This PR should fix https://github.com/coder/internal/issues/672. Related
to https://github.com/coder/coder/issues/15109.
---
 cli/clitest/clitest.go           |  6 ++++++
 cli/server.go                    |  5 ++++-
 coderd/database/pubsub/pubsub.go | 15 +++++++--------
 3 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/cli/clitest/clitest.go b/cli/clitest/clitest.go
index fbc913e7b8..8d1f5302ce 100644
--- a/cli/clitest/clitest.go
+++ b/cli/clitest/clitest.go
@@ -168,6 +168,12 @@ func StartWithAssert(t *testing.T, inv *serpent.Invocation, assertCallback func(
 		switch {
 		case errors.Is(err, context.Canceled):
 			return
+		case err != nil && strings.Contains(err.Error(), "driver: bad connection"):
+			// When we cancel the context on a query that's being executed within
+			// a transaction, sometimes, instead of a context.Canceled error we get
+			// a "driver: bad connection" error.
+			// https://github.com/lib/pq/issues/1137
+			return
 		default:
 			assert.NoError(t, err)
 		}
diff --git a/cli/server.go b/cli/server.go
index 9f55b63fc7..d9badd02d9 100644
--- a/cli/server.go
+++ b/cli/server.go
@@ -2359,6 +2359,10 @@ func ConnectToPostgres(ctx context.Context, logger slog.Logger, driver string, d
 	if err != nil {
 		return nil, xerrors.Errorf("get postgres version: %w", err)
 	}
+	defer version.Close()
+	if version.Err() != nil {
+		return nil, xerrors.Errorf("version select: %w", version.Err())
+	}
 	if !version.Next() {
 		return nil, xerrors.Errorf("no rows returned for version select")
 	}
@@ -2367,7 +2371,6 @@ func ConnectToPostgres(ctx context.Context, logger slog.Logger, driver string, d
 	if err != nil {
 		return nil, xerrors.Errorf("scan version: %w", err)
 	}
-	_ = version.Close()
 
 	if versionNum < 130000 {
 		return nil, xerrors.Errorf("PostgreSQL version must be v13.0.0 or higher! Got: %d", versionNum)
diff --git a/coderd/database/pubsub/pubsub.go b/coderd/database/pubsub/pubsub.go
index 8019754e15..c4b454abdf 100644
--- a/coderd/database/pubsub/pubsub.go
+++ b/coderd/database/pubsub/pubsub.go
@@ -552,15 +552,14 @@ func (p *PGPubsub) startListener(ctx context.Context, connectURL string) error {
 			sentErrCh = true
 		}),
 	}
-	select {
-	case err = <-errCh:
-		if err != nil {
-			_ = p.pgListener.Close()
-			return xerrors.Errorf("create pq listener: %w", err)
-		}
-	case <-ctx.Done():
+	// We don't respect context cancellation here. There's a bug in the pq library
+	// where if you close the listener before or while the connection is being
+	// established, the connection will be established anyway, and will not be
+	// closed.
+	// https://github.com/lib/pq/issues/1192
+	if err := <-errCh; err != nil {
 		_ = p.pgListener.Close()
-		return ctx.Err()
+		return xerrors.Errorf("create pq listener: %w", err)
 	}
 	return nil
 }