increase the size of txn to support vault (#14599)

* increase the size of txn to support vault

* add test, revert change to acl endpoint

* add changelog

* update test, add passing test case

* Update .changelog/14599.txt

Co-authored-by: Freddy <freddygv@users.noreply.github.com>

Co-authored-by: Freddy <freddygv@users.noreply.github.com>

.changelog/14599.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+api: Increase max number of operations inside a transaction for requests to /v1/txn (128)
+```

agent/txn_endpoint.go

@@ -17,7 +17,7 @@ const (
 	// maxTxnOps is used to set an upper limit on the number of operations
 	// inside a transaction. If there are more operations than this, then the
 	// client is likely abusing transactions.
-	maxTxnOps = 64
+	maxTxnOps = 128
 )
 
 // decodeValue decodes the value member of the given operation.

agent/txn_endpoint_test.go

@@ -798,3 +798,54 @@ func TestTxnEndpoint_NodeService(t *testing.T) {
 	}
 	assert.Equal(t, expected, txnResp)
 }
+
+func TestTxnEndpoint_OperationsSize(t *testing.T) {
+	if testing.Short() {
+		t.Skip("too slow for testing.Short")
+	}
+
+	t.Run("too-many-operations", func(t *testing.T) {
+		var ops []api.TxnOp
+		agent := NewTestAgent(t, "limits = { txn_max_req_len = 700000 }")
+
+		for i := 0; i < 130; i++ {
+			ops = append(ops, api.TxnOp{
+				KV: &api.KVTxnOp{
+					Verb:  api.KVSet,
+					Key:   "key",
+					Value: []byte("test"),
+				},
+			})
+		}
+
+		req, _ := http.NewRequest("PUT", "/v1/txn", jsonBody(ops))
+		resp := httptest.NewRecorder()
+		raw, err := agent.srv.Txn(resp, req)
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "Transaction contains too many operations")
+		require.Nil(t, raw)
+		agent.Shutdown()
+	})
+
+	t.Run("allowed", func(t *testing.T) {
+		var ops []api.TxnOp
+		agent := NewTestAgent(t, "limits = { txn_max_req_len = 700000 }")
+
+		for i := 0; i < 128; i++ {
+			ops = append(ops, api.TxnOp{
+				KV: &api.KVTxnOp{
+					Verb:  api.KVSet,
+					Key:   "key",
+					Value: []byte("test"),
+				},
+			})
+		}
+
+		req, _ := http.NewRequest("PUT", "/v1/txn", jsonBody(ops))
+		resp := httptest.NewRecorder()
+		raw, err := agent.srv.Txn(resp, req)
+		require.NoError(t, err)
+		require.NotNil(t, raw)
+		agent.Shutdown()
+	})
+}