Devicelab "smoke_catalina_hot_mode_dev_cycle_ios__benchmark" failure "Error while starting Kernel isolate task"

[christopherfujino]

https://flutter-dashboard.appspot.com/api/get-log?ownerKey=ahFmbHV0dGVyLWRhc2hib2FyZHJfCxIJQ2hlY2tsaXN0Ij9mbHV0dGVyL2ZsdXR0ZXIvbWFzdGVyL2IxOGYxYjgxZmUwOWExZjJiZWEzOWVhYWM5Y2M3MDllMWFjNjAwY2YMCxIEVGFzaxiAgJitlZL0Cww

2020-11-24T13:18:51.833071: stdout: Performing hot restart...                                       
2020-11-24T13:18:51.833173: stdout: Restarted application in 1,622ms.
2020-11-24T13:19:01.844560: stdout: Benchmarking hot reload
2020-11-24T13:19:02.336088: stdout: Performing hot reload...                                        
2020-11-24T13:19:02.341727: stdout: Reloaded 0 libraries in 491ms.
2020-11-24T13:19:02.344558: stdout: 
2020-11-24T13:19:06.671623: stderr: Hot reload was rejected:
2020-11-24T13:19:06.671728: stderr: Error while starting Kernel isolate task.
stderr: Try performing a hot restart instead.
2020-11-24T13:19:06.672008: stdout: Performing hot reload...                                        
2020-11-24T13:19:06.672084: stdout: Try again after fixing the above error(s).
2020-11-24T14:16:27.981250: Task execution finished

[christopherfujino]

This could have been broken by any of the following 3 engine rolls:

• e5c4384
• 8241757
• 13ce828

The test hasn't been back filled for any of these engine rolls yet:

[iskakaushik]

I'm pausing the engine->framework roller until this is resolved.

[christopherfujino]

This appears to be a pre-existing flake, I can find the same failure as early as 8e73bab (and likely earlier)

https://flutter-dashboard.appspot.com/api/get-log?ownerKey=ahFmbHV0dGVyLWRhc2hib2FyZHJfCxIJQ2hlY2tsaXN0Ij9mbHV0dGVyL2ZsdXR0ZXIvbWFzdGVyLzhlNzNiYWI5NGM2MDUxMzE3YzlmYTQyNzlhMzczM2I2ZWUyYTNlZjIMCxIEVGFzaxiAgJi5tqKfCgw

[christopherfujino]

Since this test repeatedly fails on b18f1b8, while it passed on the previous, I landed a revert to see if it will fix the tree #71180

[keyonghan]

Unfortunately it hangs with the same error on the revert.

[christopherfujino]

Ok, I will re-land goderbauer's commit.

[christopherfujino]

This test was marked flaky in #71188

[Piinks]

I am going to downgrade this since it is not breaking the build anymore in its flaky state. Currently tasks are backed up so we are waiting to evaluate if the flakiness has persisted.

[jonahwilliams]

The error message comes from https://github.com/dart-lang/sdk/blob/55bb15a8cbbe7c5ff2242d74c5e18370ba9b6922/runtime/vm/kernel_isolate.cc#L1016

Unfortunately it doesn't tell us much about what failed. Ideally there would be a verbose mode that would include more error logs during the hot reload. @zanderso @aam do you know what flag controls OS::PrintErr?

[zanderso]

The logging in that file is guarded by the Dart VM command line flag --trace-kernel.

[aam]

@jonahwilliams asked:

do you know what flag controls OS::PrintErr?

There is no generic flag for that.
You can try adding --trace-reload and --trace-reload-verbose flags that enable more trace prints during hot reload to https://github.com/flutter/engine/blob/master/runtime/dart_vm.cc#L63.

[jonahwilliams]

The latest run of this is passing

[jonahwilliams]

Test is still passing, might have been a device issue? I'm lowering the priority but still plan to up the verbosity

[jonahwilliams]

removing assignment because I will be OOO

[github-actions]

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