Fix flaky test with transactions

CHANGELOG.md

@@ -6,6 +6,7 @@
 __BREAKING CHANGES:__
 - NEW: Added file upload restriction. File upload is now only allowed for authenticated users by default for improved security. To allow file upload also for Anonymous Users or Public, set the `fileUpload` parameter in the [Parse Server Options](https://parseplatform.org/parse-server/api/master/ParseServerOptions.html). [#7071](https://github.com/parse-community/parse-server/pull/7071). Thanks to [dblythy](https://github.com/dblythy), [Manuel Trezza](https://github.com/mtrezza).
 ___
+- IMPROVE: Retry transactions on MongoDB when it fails due to transient error [#7187](https://github.com/parse-community/parse-server/pull/7187). Thanks to [Antonio Davi Macedo Coelho de Castro](https://github.com/davimacedo).
 - UPGRADE: Bump tests to use Mongo 4.4.4 [#7184](https://github.com/parse-community/parse-server/pull/7184). Thanks to [Antonio Davi Macedo Coelho de Castro](https://github.com/davimacedo).
 - NEW (EXPERIMENTAL): Added new page router with placeholder rendering and localization of custom and feature pages such as password reset and email verification. **Caution, this is an experimental feature that may not be appropriate for production.** [#6891](https://github.com/parse-community/parse-server/issues/6891). Thanks to [Manuel Trezza](https://github.com/mtrezza).
 - NEW: Added convenience method `Parse.Cloud.sendEmail(...)` to send email via email adapter in Cloud Code. [#7089](https://github.com/parse-community/parse-server/pull/7089). Thanks to [dblythy](https://github.com/dblythy)

spec/ParseServerRESTController.spec.js

@@ -197,7 +197,7 @@ describe('ParseServerRESTController', () => {
           .then(() => {
             spyOn(databaseAdapter, 'createObject').and.callThrough();
 
-            RESTController.request('POST', 'batch', {
+            return RESTController.request('POST', 'batch', {
               requests: [
                 {
                   method: 'POST',
@@ -218,7 +218,7 @@ describe('ParseServerRESTController', () => {
               expect(response[1].success.objectId).toBeDefined();
               expect(response[1].success.createdAt).toBeDefined();
               const query = new Parse.Query('MyObject');
-              query.find().then(results => {
+              return query.find().then(results => {
                 expect(databaseAdapter.createObject.calls.count()).toBe(2);
                 expect(databaseAdapter.createObject.calls.argsFor(0)[3]).toBe(
                   databaseAdapter.createObject.calls.argsFor(1)[3]
@@ -230,7 +230,8 @@ describe('ParseServerRESTController', () => {
                 done();
               });
             });
-          });
+          })
+          .catch(done.fail);
       });
 
       it('should not save anything when one operation fails in a transaction', done => {

src/Adapters/Storage/Mongo/MongoStorageAdapter.js

@@ -1046,9 +1046,20 @@ export class MongoStorageAdapter implements StorageAdapter {
   }
 
   commitTransactionalSession(transactionalSection: any): Promise<void> {
-    return transactionalSection.commitTransaction().then(() => {
-      transactionalSection.endSession();
-    });
+    const commit = retries => {
+      return transactionalSection
+        .commitTransaction()
+        .catch(error => {
+          if (error && error.hasErrorLabel('TransientTransactionError') && retries > 0) {
+            return commit(retries - 1);
+          }
+          throw error;
+        })
+        .then(() => {
+          transactionalSection.endSession();
+        });
+    };
+    return commit(5);
   }
 
   abortTransactionalSession(transactionalSection: any): Promise<void> {

src/ParseServerRESTController.js

@@ -48,44 +48,60 @@ function ParseServerRESTController(applicationId, router) {
     }
 
     if (path === '/batch') {
-      let initialPromise = Promise.resolve();
-      if (data.transaction === true) {
-        initialPromise = config.database.createTransactionalSession();
-      }
-      return initialPromise.then(() => {
-        const promises = data.requests.map(request => {
-          return handleRequest(request.method, request.path, request.body, options, config).then(
-            response => {
-              if (options.returnStatus) {
-                const status = response._status;
-                delete response._status;
-                return { success: response, _status: status };
+      const batch = transactionRetries => {
+        let initialPromise = Promise.resolve();
+        if (data.transaction === true) {
+          initialPromise = config.database.createTransactionalSession();
+        }
+        return initialPromise.then(() => {
+          const promises = data.requests.map(request => {
+            return handleRequest(request.method, request.path, request.body, options, config).then(
+              response => {
+                if (options.returnStatus) {
+                  const status = response._status;
+                  delete response._status;
+                  return { success: response, _status: status };
+                }
+                return { success: response };
+              },
+              error => {
+                return {
+                  error: { code: error.code, error: error.message },
+                };
               }
-              return { success: response };
-            },
-            error => {
-              return {
-                error: { code: error.code, error: error.message },
-              };
-            }
-          );
-        });
-        return Promise.all(promises).then(result => {
-          if (data.transaction === true) {
-            if (result.find(resultItem => typeof resultItem.error === 'object')) {
-              return config.database.abortTransactionalSession().then(() => {
-                return Promise.reject(result);
-              });
-            } else {
-              return config.database.commitTransactionalSession().then(() => {
+            );
+          });
+          return Promise.all(promises)
+            .then(result => {
+              if (data.transaction === true) {
+                if (result.find(resultItem => typeof resultItem.error === 'object')) {
+                  return config.database.abortTransactionalSession().then(() => {
+                    return Promise.reject(result);
+                  });
+                } else {
+                  return config.database.commitTransactionalSession().then(() => {
+                    return result;
+                  });
+                }
+              } else {
                 return result;
-              });
-            }
-          } else {
-            return result;
-          }
+              }
+            })
+            .catch(error => {
+              if (
+                error &&
+                error.find(
+                  errorItem => typeof errorItem.error === 'object' && errorItem.error.code === 251
+                ) &&
+                transactionRetries > 0
+              ) {
+                return batch(transactionRetries - 1);
+              }
+              throw error;
+            });
         });
-      });
+      };
+      return batch(5);
     }
 
     let query;

src/batch.js

@@ -83,49 +83,66 @@ function handleBatch(router, req) {
     req.config.publicServerURL
   );
 
-  let initialPromise = Promise.resolve();
-  if (req.body.transaction === true) {
-    initialPromise = req.config.database.createTransactionalSession();
-  }
-
-  return initialPromise.then(() => {
-    const promises = req.body.requests.map(restRequest => {
-      const routablePath = makeRoutablePath(restRequest.path);
-
-      // Construct a request that we can send to a handler
-      const request = {
-        body: restRequest.body,
-        config: req.config,
-        auth: req.auth,
-        info: req.info,
-      };
-
-      return router.tryRouteRequest(restRequest.method, routablePath, request).then(
-        response => {
-          return { success: response.response };
-        },
-        error => {
-          return { error: { code: error.code, error: error.message } };
-        }
-      );
-    });
+  const batch = transactionRetries => {
+    let initialPromise = Promise.resolve();
+    if (req.body.transaction === true) {
+      initialPromise = req.config.database.createTransactionalSession();
+    }
 
-    return Promise.all(promises).then(results => {
-      if (req.body.transaction === true) {
-        if (results.find(result => typeof result.error === 'object')) {
-          return req.config.database.abortTransactionalSession().then(() => {
-            return Promise.reject({ response: results });
-          });
-        } else {
-          return req.config.database.commitTransactionalSession().then(() => {
+    return initialPromise.then(() => {
+      const promises = req.body.requests.map(restRequest => {
+        const routablePath = makeRoutablePath(restRequest.path);
+
+        // Construct a request that we can send to a handler
+        const request = {
+          body: restRequest.body,
+          config: req.config,
+          auth: req.auth,
+          info: req.info,
+        };
+
+        return router.tryRouteRequest(restRequest.method, routablePath, request).then(
+          response => {
+            return { success: response.response };
+          },
+          error => {
+            return { error: { code: error.code, error: error.message } };
+          }
+        );
+      });
+
+      return Promise.all(promises)
+        .then(results => {
+          if (req.body.transaction === true) {
+            if (results.find(result => typeof result.error === 'object')) {
+              return req.config.database.abortTransactionalSession().then(() => {
+                return Promise.reject({ response: results });
+              });
+            } else {
+              return req.config.database.commitTransactionalSession().then(() => {
+                return { response: results };
+              });
+            }
+          } else {
             return { response: results };
-          });
-        }
-      } else {
-        return { response: results };
-      }
+          }
+        })
+        .catch(error => {
+          if (
+            error &&
+            error.response &&
+            error.response.find(
+              errorItem => typeof errorItem.error === 'object' && errorItem.error.code === 251
+            ) &&
+            transactionRetries > 0
+          ) {
+            return batch(transactionRetries - 1);
+          }
+          throw error;
+        });
     });
-  });
+  };
+  return batch(5);
 }
 
 module.exports = {