Kotlin Coroutines: How to continue work even when children tasks fail or timeout

This talk was about sharing our learnings with the community while using Kotlin Coroutines for an interesting use case we had in our project. We are barely scratching the surface but I felt it might help others in making some better decisions with parent-child setup if they know the different uses of certain CoroutineScopes.

This talk was presented at Kotlin User Group Munich (KTUG) meetup hosted at KI labs.

Meetup link: https://www.meetup.com/Kotlin-User-Group-Munich/events/257927489/
Talk Recording: https://www.pscp.tv/w/1RDxlqmypQjKL

Transcript

1. How to continue even if Children Timeouts or Fail Wahib Ul Haq
3. Coroutine are light-weight threads, with little overhead and easier to be controlled by the developers.
5. Interesting Use Case
6. Event A Event B Event C Event D Computation Computation Computation Time Taken Certain Limit
15. What if there is an exception in one of the children’s tasks?
25. The first exception wins
30. This scope waits for the completion of all its children and in case of a crash the scope cancels all children.
32. Supervision Scope
33. It propagates cancellation only downwards and cancels all children only if it has failed itself. Difference #1
34. Child’s failure is not propagated to the parent. Hence, every child should handle its exception by itself. Difference #2
45. Use Coroutine Scope if you want your parent job to fail if one of the children fails
46. Use Coroutine Scope if you want your parent job to fail if one of the children fails Use Supervision Scope if you want your parent job to complete in case of failure of one or more of children jobs
47. Use Coroutine Scope if you want your parent job to fail if one of the children fails Use Supervision Scope if you want your parent job to complete in case of failure of one or more of children jobs CoroutineExceptionHandler can be used to replace try /catch blocks and handle exceptions in a centralised and cleaner way
48. Use Coroutine Scope if you want your parent job to fail if one of the children fails Use Supervision Scope if you want your parent job to complete in case of failure of one or more of children jobs CoroutineExceptionHandler can be used to replace try /catch blocks and handle exceptions in a centralised and cleaner way InvokeOnInvocation() can be used to react to changes like when parent job completes (gracefully or not) or Timeout Cancellation happens
49. https://kotlinlang.org/docs/reference/coroutines/exception-handling.html Helpful Resource
50. Thanks for listening! @wahibhaq