what is a Trigger Service Retry Limit, how to implement?

When building a trigger, you can specify a retry limit for the trigger service. The retry limit indicates the maximum number of times the Integration Server re-executes the trigger service when the trigger service fails because of a run-time exception. A run-time exception (specifically, an ISRuntimeException) occurs when the trigger service catches, and wraps a transient error and rethrows it as a run-time exception.