fix: name the missing RDS engine image instead of answering ServerInternal

spinifex/handlers/rds/launch.go

@@ -52,6 +52,24 @@ const (
 // validation failure rather than launching something else.
 var ErrEngineAMINotFound = errors.New("rds: no AMI found for engine")
 
+// The catalog registers every engine's system image under this prefix, so the
+// error can name the image an operator has to import.
+const engineImageNamePrefix = "spinifex-rds-"
+
+// An engine image no deployment ever imported is a gap no retry closes, so the
+// failure carries a code: a bare error resolves to ServerInternal, which the
+// caller reads as a transient fault and retries.
+func engineAMINotFound(engine, version string) error {
+	requested := "an engine image for " + engine
+	if version != "" {
+		requested = "version " + version + " for " + engine
+	}
+	return fmt.Errorf("%w: %w", ErrEngineAMINotFound, awserrors.Errorf(
+		awserrors.ErrorInvalidParameterCombination,
+		"Cannot find %s; this deployment has no %s%s system image installed",
+		requested, engineImageNamePrefix, engine))
+}
+
 type launchVPCProvisioner interface {
 	CreateNetworkInterface(ctx context.Context, input *ec2.CreateNetworkInterfaceInput, accountID string) (*ec2.CreateNetworkInterfaceOutput, error)
 	DeleteNetworkInterface(ctx context.Context, input *ec2.DeleteNetworkInterfaceInput, accountID string) (*ec2.DeleteNetworkInterfaceOutput, error)
@@ -460,7 +478,7 @@ func resolveEngineAMI(ctx context.Context, amiSvc launchAMIResolver, engine, ver
 		return "", fmt.Errorf("rds: describe %s AMI: %w", engine, err)
 	}
 	if out == nil {
-		return "", fmt.Errorf("%w: %s %s", ErrEngineAMINotFound, engine, version)
+		return "", engineAMINotFound(engine, version)
 	}
 
 	// Several builds of one engine version can be registered; skip malformed
@@ -485,7 +503,7 @@ func resolveEngineAMI(ctx context.Context, amiSvc launchAMIResolver, engine, ver
 		}
 	}
 	if newestID == "" {
-		return "", fmt.Errorf("%w: %s %s", ErrEngineAMINotFound, engine, version)
+		return "", engineAMINotFound(engine, version)
 	}
 	if matches > 1 {
 		slog.WarnContext(ctx, "rds: multiple AMIs match the requested engine; using newest",

spinifex/handlers/rds/launch_test.go

@@ -928,5 +928,41 @@ func TestLaunchDBInstanceVMFailsWithoutAnEngineAMI(t *testing.T) {
 	_, err := LaunchDBInstanceVM(t.Context(), h.deps(), testLaunchInput())
 	require.ErrorIs(t, err, ErrEngineAMINotFound,
 		"a missing engine image must be a named failure, never a fallback to some other AMI")
+	code, _, ok := awserrors.ResolveErrorDetail(err)
+	require.True(t, ok, "the launch must not swallow the code on its way out")
+	assert.Equal(t, awserrors.ErrorInvalidParameterCombination, code)
 	assert.Empty(t, h.enis.created)
 }
+
+func TestResolveEngineAMINotFoundCarriesAClientCode(t *testing.T) {
+	t.Parallel()
+	h := newLaunchHarness()
+	h.images.images = nil
+
+	_, err := resolveEngineAMI(t.Context(), h.images, "postgres", "18")
+	require.ErrorIs(t, err, ErrEngineAMINotFound)
+
+	code, message, ok := awserrors.ResolveErrorDetail(err)
+	require.True(t, ok,
+		"an uncoded error reaches the caller as a retried ServerInternal, which says nothing about what is missing")
+	assert.Equal(t, awserrors.ErrorInvalidParameterCombination, code)
+	assert.Contains(t, message, "version 18 for postgres")
+	assert.Contains(t, message, "spinifex-rds-postgres",
+		"the message names the image an operator has to import")
+}
+
+func TestResolveEngineAMINotFoundWithoutARequestedVersion(t *testing.T) {
+	t.Parallel()
+	h := newLaunchHarness()
+	h.images.images = nil
+
+	_, err := resolveEngineAMI(t.Context(), h.images, "mariadb", "")
+	require.ErrorIs(t, err, ErrEngineAMINotFound)
+
+	code, message, ok := awserrors.ResolveErrorDetail(err)
+	require.True(t, ok)
+	assert.Equal(t, awserrors.ErrorInvalidParameterCombination, code)
+	assert.Contains(t, message, "an engine image for mariadb",
+		"an unset version must not read back as an empty one")
+	assert.Contains(t, message, "spinifex-rds-mariadb")
+}