Merge branch 'zj-env-var-disable-transactions' into 'master'

transactions: Allow disabling with an env var

See merge request gitlab-org/gitaly!2853

3 files changed, 33 insertions, 0 deletions

diff --git a/changelogs/unreleased/zj-env-var-disable-transactions.yml b/changelogs/unreleased/zj-env-var-disable-transactions.yml
new file mode 100644
index 000000000..b76cae272
--- /dev/null
+++ b/changelogs/unreleased/zj-env-var-disable-transactions.yml
@@ -0,0 +1,5 @@
+---
+title: 'transactions: Allow disabling with an env var'
+merge_request: 2853
+author:
+type: changed
diff --git a/internal/praefect/coordinator.go b/internal/praefect/coordinator.go
index fa974a4d2..c5f9963b6 100644
--- a/internal/praefect/coordinator.go
+++ b/internal/praefect/coordinator.go
@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"os"
 
 	"github.com/golang/protobuf/proto"
 	"github.com/grpc-ecosystem/go-grpc-middleware/logging/logrus/ctxlogrus"
@@ -129,7 +130,14 @@ func init() {
 	}
 }
 
+const gitalyDisabledRefEnvVar = "GITALY_DISABLE_REF_TRANSACTIONS"
+
 func shouldUseTransaction(ctx context.Context, method string) bool {
+	// Disabling based on a environment variable, as a poor mans feature flag.
+	if _, ok := os.LookupEnv(gitalyDisabledRefEnvVar); ok {
+		return false
+	}
+
 	condition, ok := transactionRPCs[method]
 	if !ok {
 		return false
diff --git a/internal/praefect/coordinator_test.go b/internal/praefect/coordinator_test.go
index 45e5eb917..cddcbb4ba 100644
--- a/internal/praefect/coordinator_test.go
+++ b/internal/praefect/coordinator_test.go
@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"io/ioutil"
+	"os"
 	"sync"
 	"testing"
 	"time"
@@ -1196,6 +1197,25 @@ func TestStreamDirectorStorageScopeError(t *testing.T) {
 	})
 }
 
+func TestDisabledTransactionsWithEnvVar(t *testing.T) {
+	os.Setenv(gitalyDisabledRefEnvVar, "1")
+	defer os.Unsetenv(gitalyDisabledRefEnvVar)
+
+	ctx, cancel := testhelper.Context()
+	defer cancel()
+
+	var rpcname string
+	for name, enabledFn := range transactionRPCs {
+		if enabledFn(ctx) {
+			rpcname = name
+			break
+		}
+	}
+
+	require.NotEmpty(t, rpcname, "no enabled reference transaction RPCs")
+	require.False(t, shouldUseTransaction(ctx, rpcname))
+}
+
 func requireScopeOperation(t *testing.T, registry *protoregistry.Registry, fullMethod string, scope protoregistry.Scope, op protoregistry.OpType) {
 	t.Helper()