Rollback error handler
The Rollback error handler stops the run and reverts changes made by modules that support transactions. They always use a database app, like MySQL or Data store. cannot undo actions made by modules that don't support transactions, like Gmail > Send an email or Dropbox > Delete a file.
The bundle that caused the error doesn't continue in the flow. In addition, doesn't process any remaining bundles.
marks the run as an error in the history. won't disable the because of consecutive errors.
Modules that support transactions are labeled with the "ACID" label.
Before you use the Rollback or Commit error handlers, take a look at the auto commit scenario setting first.
For example: This demo contains five modules. The is useful for tests and showing the effect of an error handler:
- JSON - Parse JSON provides test data in the form of an array of three record IDs.
- Iterator splits the array into individual bundles.
- Data store - Update a record: Updates the data in the data store.
Data store - Update a record: This module updates the data again. This time the module works differently. In the module mapping, there is a mapping that intentionally creates an error:
The mapping inserts a null value into the required Key field, which always creates the BundleValidationError.
Having two data store modules doing the same thing, but one of them failing, will make a good example for the Commit and Rollback error handlers.
- Slack - Send a message: Sends a message to a private testing channel.
This is how the example looks:
When we would run the example , we would get the BundleValidationError:
If we added the Rollback error handler to the Update a record module, the Rollback error handler would stop processing the bundle in the . wouldn't process the remaining bundles.
Let's check the data in the data store as well.
Before running the , the data store contained the following data:
The mappings for the Update a record modules. The first module updates the ID column to the number 4 and the Name column to the text Test 4.
The second module updates the ID column to the number 5 and the Name column to the text Test 5.
If you disable the Auto-commit option in the settings, reverts the changes that happened when was processing the bundle in modules that support transactions.
- The first bundle of data gets through the flow successfully and updates the first row of data in the data store both times. The first row contains the update from the second Update a record module: ID = 5, Name = Test 5.
- The second bundle gets to the first Update a record module successfully, but causes an error in the second module. The Rollback error handler reverts the update from the second bundle and stops the .
- doesn't update the third row because the Rollback error handler stopped the run already. The data in the third row remain the same: ID = 3, Name = Test 3.
If you keep the Auto-commit option enabled, reverts the changes made by the module that output the error if the module supports transactions.
- The first bundle of data gets through the flow successfully and updates the first row of data in the data store both times. commits all changes and they cannot be rolled back later.The first row contains the update from the second Update a record module: ID = 5, Name = Test 5.
- The second bundle gets to the first Update a record module successfully. commits all changes and they cannot be rolled back later. The second bundle causes an error in the second module.The Rollback error handler prevents the update in the second module and stops the . The second row contains the update from the first module only: ID = 4, Name = Test 4.
- Make doesn't update the third row because the Rollback error handler stopped the run already. The data in the third row remain the same: ID = 3, Name = Test 3.
You can use the Rollback error handler to stop the run and undo changes when the module outputs an error.
For more information about error handling strategies check the overview of error handling.
With the Rollback error handler, you can stop the and undo changes when the module outputs an error. You can only undo changes in modules that support transactions.
Modules that support transactions are labeled with the "ACID" label.
Before you use the Rollback or Commit error handlers, take a look at the auto commit scenario setting first.
For example, the following outputs an error in the Data Store app module:
To stop the and undo changes where possible when an error happens, follow the steps:
- Right-click the module that is causing the error. In the menu, select Add error handler.
- Select the Rollback error handler.
- Optional: Go to settings and disable the Auto-commit option.When an error happens, the module that outputs the error reverts changes if the module supports transactions. If you disable the Auto-commit option, all modules in the that support transactions undo changes.
- Save your .
You added the Rollback error handler to your . When an error occurs in the Data store module, the stops and reverts changes made by the erroring bundle in modules that support transactions.