action #12836

Updated by okurz over 4 years ago

## motivation 

 or also: When testing the kernel, soft-lockups can occur, for example: 
 [    140.140055] NMI watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [kworker/u2:6:2060] 
 [    154.592130] BUG: workqueue lockup - pool cpus=0 flags=0x4 nice=0 stuck for 40s! 
 [    200.140070] NMI watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [kworker/u2:6:2060] 

 Reproducing these is quite difficult, as is gathering logfiles (the machine hangs.. ). 
 In order to be usable for kernel testing, and investigation of error cause, attaching to  
 the VM with a debugger is necessary in this case. 
 So for kernel tests, instead of shutting down Qemu, the state of the machine must be  
 preserved in case the job does not finish prior to the timeout, otherwise it will not  
 be possible to identify the cause of the lockup. 

 ## user story 
 As a investigator of non-obvious test failures I want (sometimes) to preserve the virtual machine (keep it running) or the disk image to be able to investigate an error. 

 ## acceptance criteria 
 * **AC1**: either disk images or virtual machines are preserved in case of failures on demand or automatically 
 * **AC2:** An openQA triggered VM is not powered off on demand whenever a (critical) failure appears 
 * **AC3:** Any VM is not kept around indefinitely, e.g. still aborted and shutdown after a timeout 


 ## Suggestions 
 * Add a flag in os-autoinst to not shutdown immediately when the job fails but keep running 
 * Crosscheck that if MAX_JOB_TIME is exceeded in openQA the job and VM is still terminated 
 * Add documentation with hints how to use this mode, e.g. to use <new flag> and MAX_JOB_TIME in combination to keep machines around on demand for a limited time 
 * Evaluate potential followup to keep machines around potentially longer, e.g. keep failed machines running for limited time automatically, use live migration or memory dumps to "pause" a machine where it can be restored from on demand 
 * Optional: Add more straightforward access to this feature, e.g. GUI support 

 ## Further details suggestion 
 It might be feasible to let virtual machines run for some time, e.g. 1 hour, in case of a failure, which can give investigators some time to debug or at least copy the image while it's running. Also, the image could be "published" and stored and cleaned according to existing or to-be-defined GRU-cleanup rules. 

 An alternative would be for an openQA operator to request the preservation by a variable. E.g. clone a consistently failing job and set variable. PUBLISH_HDD_1 is near but does not work as it only publishes on success. Another variable could be set to publish regardless of result or another variable altogether to store "failed" images, e.g. PUBLISH_FAILED_HDD_1.