Error handling
- 2. Error handling Mule ESB provides numerous options for handling errors. Faults that occur within Mule are referred to as exceptions; when an activity in your Mule instance fails, Mule throws an exception. To manage these exceptions, Mule allows you to configure exception strategies. From high level perspective, mule fall in two categories: System exceptions Messaging exceptions
- 3. System exceptions Mule invokes a System Exception Strategy when an exception is thrown at the system-level (i.e., when no message is involved, exceptions are handled by system exception strategies). For example, system exception strategies handle exceptions that occur: During application start-up When a connection to an external system fails When a system exception strategy occurs, Mule sends an exception notification to registered listeners, logs the exception, and — if the exception was caused by a connection failure — executes the reconnection strategy. System Exception Strategies are not configurable in Mule.
- 4. Messaging exceptions Mule invokes a Messaging Exception Strategy whenever an exception is thrown within a flow (i.e., whenever a message is involved, exceptions are handled by messaging exception strategies). In this case, when any messaging exception occurs then current mule flow stops and flow goes to the exception strategies flow which handles all the exceptions which was occurred. Mule supports five messaging exception strategies as described in further slides.
- 5. Default exception strategies Use - Defined and implicitly applied by default to handle all messaging exceptions that are thrown in Mule applications Transaction error handling - When a message throws an exception, the default exception strategy rolls back the message and logs the exception.
- 6. Catch exception strategies Use - Define a catch exception strategy to customize the way Mule handles any exception. Catch exception strategies consume inbound messages. Transaction error handling - When a message throws an exception, the catch exception strategy always commits the transaction and consumes the message.
- 7. Rollback exception strategy Use - Define a rollback exception strategy to ensure that a message that throws an exception in a flow is rolled back for reprocessing (if the message source supports redelivery). Rollback exception strategies do not consume inbound messages. Transaction error handling - When a message throws an exception, the rollback exception strategy makes one or more attempts to rollback the message and redeliver it for processing (if the message source supports redelivery). If the message exceeds its redelivery attempts, then the rollback exception strategy commits the failed transaction and consumes the message.
- 8. Reference exception strategy Use - Define a reference exception strategy to refer and adhere to the error handling parameters defined in a global catch, rollback or choice exception strategy. Transaction error handling - When a message throws an exception, the reference exception strategy refers and adheres to the error handling parameters defined in a global catch, rollback or choice exception strategy. (The reference exception strategy itself never actually performs any rollback, commit, or consume activities.)
- 9. Choice exception strategy Use - Define a choice exception strategy to customize the way Mule handles a message that throws an exception based on the message’s content at the moment it throws the exception. Transaction error handling - When a message throws an exception, the choice exception strategy makes a decision about where to route the message for further processing. (The choice exception strategy itself never actually performs any rollback, commit, or consume activities.)
- 10. Characteristics Each flow can contain only one exception strategy. Each exception strategy can contain any number of message processors. Choice exception strategies can contain one or more catch and/or rollback exception strategies. (Rollback and catch exception strategies cannot, however, contain other exception strategies.)
- 11. Thanks