[Bug 1915678] Re: iSCSI+Multipath: Volume attachment hungs if sessiong scanning fails

[Brett Milford]

** Also affects: python-os-brick (Ubuntu)
   Importance: Undecided
       Status: New

** Also affects: python-os-brick (Ubuntu Focal)
   Importance: Undecided
       Status: New

** Also affects: python-os-brick (Ubuntu Bionic)
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/1915678

Title:
  iSCSI+Multipath: Volume attachment hungs if sessiong scanning fails

Status in os-brick:
  Fix Released
Status in python-os-brick package in Ubuntu:
  New
Status in python-os-brick source package in Bionic:
  New
Status in python-os-brick source package in Focal:
  New

Bug description:
  Currently we execute login to iscsi portals and device discovery in
  multiple threads concurrently when multipath is enabled.

  However if some commands like "iscsiadm -m session" fail, the thread can abort immediately without updating any counters like failed_logins or stopped_threads properly, because there are no try-except block to catch  exceptions.
  However the main thread keeps waiting until these counters are updated, and this results in stuck of volume attachment process.

  This issue was initially reported in downstream bug https://bugzilla.redhat.com/show_bug.cgi?id=1923975 , and maybe is caused by a bug in iscsiadm command.
  However we should handle the error more properly because current behavior requires operators to restart services like cinder-volume to resolve the stuck.

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