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Swift Debugging


If an application procedure execution fails, Swift will attempt that execution again repeatedly until it succeeds, up until the limit defined in the execution.retries configuration property.

Site selection will occur for retried jobs in the same way that it happens for new jobs. Retried jobs may run on the same site or may run on a different site.

If the retry limit execution.retries is reached for an application procedure, then that application procedure will fail. This will cause the entire run to fail - either immediately (if the lazy.errors property is false) or after all other possible work has been attempted (if the lazy.errors property is true).

With or without lazy errors, each app is re-tried times before it is considered failed for good. An app that has failed but still has retries left will appear as "Failed but can retry".

Without lazy errors, once the first (time-wise) app has run out of retries, the whole run is stopped and the error reported.

With lazy errors, if an app fails after all retries, its outputs are marked as failed. All apps that depend on failed outputs will also fail and their outputs marked as failed. All apps that have non-failed outputs will continue to run normally until everything that can proceed completes.

For example, if you have:

foreach x in [1:1024] {

If the first started app fails, all the other ones can still continue, and if they don’t otherwise fail, the run will only terminate when all 1023 of them will complete.

So basically the idea behind lazy errors is to run EVERYTHING that can safely be run before stopping.

Some types of errors (such as internal swift errors happening in an app thread) will still stop the run immediately even in lazy errors mode. But we all know there are no such things as internal swift errors :)


In this page (written and validated by ) you learned about Swift Debugging . What's Next? If you are interested in completing Swift tutorial, your next topic will be learning about: Swift Restarts.

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