exception strategies in mulesoft anypoint studio
TRANSCRIPT
Exception Strategies in Mulesoft Anypoint Studio
Introduction
Mulesoft provides various ways to handle exceptions. Faults in Mule are
generally referred to as exceptions. Mule exceptions can be divided into two
categories:
System exceptions are generally invoked when the exception is thrown at
system level (i.e., when no message is invoked). This type of error occurs during
application startup when there is a connection failure with external systems — i.e.,
let's say Mule is trying to establish a connection with a JDBC database to fetch
and read messages. If the connection fails, Mule invokes the system exception
strategy.
Messaging exceptions are generally invoked when the messaging exception
strategy is thrown into the flow.
Exception Strategies
Mule provides various exception strategies. Below is listed some of exception
strategies
Catch Exception Strategy
Choice Exception Strategy
Reference Exception Strategy
Rollback Exception Strategy
Catch Exception Strategy
The catch exception strategy catches all of the exceptions within the parent
flow and processes them, overriding the default exception strategy. Further, you
can use the catch exception strategy to:
Avoid propagating exceptions to inbound connectors.
Avoid propagating exceptions to parents via flow reference components.
Ensure that the transaction processed by the flow will not roll back when the error
occurs.
Reference Exception Strategy
You can create one or more global exception strategies in your Mule
application to reuse in your flows. First, create a global exception strategy, then
add a reference strategy exception to the flow to apply the error-handling
behavior of your new global catch exception strategy.
Choice Exception Strategy
You can define the choice exception strategy to customize how Mule handles
the message that throws the exception based on the message's exception type
at the moment it throws the exception.
Choice exception strategy contains one or more exception or rollback strategies.
Choice exception strategy cannot be nested with other choice exception
strategies.
Any Mule expression evaluator can be used as the expression attribute of an
exception strategy.
Rollback Exception Strategy
You can define the rollback exception strategy to ensure that the message
throws an error in the flow that can be rolled back for re-processing.
Rollback exception strategy can potentially create an infinite loop during
message failure. The rollback exception strategy catches the error and rolls the
message for reprocessing; the message throws error again; the rollback
exception strategy rolls the message again for reprocessing; and so on.
To avoid this infinite loop and responsibly manage unresolvable errors, you can
apply two limitations to a rollback exception strategy:
Define the maximum number of times that the rollback exception strategy
attempts to redeliver the message for processing.
Define a flow to handle messages that exceed the maximum number of
redelivery attempts.
Various ways of defining the Exception Strategy
Define Error Handler Within Mule flow
You can define the exception strategy within a flow and it will not be referenced by
other flows within the Mule application.
Define Global Error Handler
You can define a global error handler that can be referenced from any flow (except
sub-flows, which inherit the calling flow error handler) using reference flow strategy.
Define Custom Default Global Error Handler
You can define custom default global error handlers that will become the default
error handler for your flows within the Mule application unless one of the above
options is used in the flow.
Thank You