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

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You have been subscribed to a public bug by Brett Milford (brettmilford):

[Impact]

 * 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.
 * The main thread keeps waiting until these counters are updated, and this results in stuck of volume attachment process.

[Test Case]

 * Deploy Cinder with an iSCSI driver and multipath enabled.

 * TBC.

[Where problems could occur]

 * Change primarily introduces error handling and doesn't change implementation details.
   As such we may see an error condition logged.

[Other Info]

 * -

--- Original 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.

** Affects: os-brick
     Importance: High
         Status: Fix Released

** Affects: python-os-brick (Ubuntu)
     Importance: Undecided
         Status: Fix Released

** Affects: python-os-brick (Ubuntu Bionic)
     Importance: Undecided
     Assignee: Brett Milford (brettmilford)
         Status: In Progress

** Affects: python-os-brick (Ubuntu Focal)
     Importance: Undecided
     Assignee: Brett Milford (brettmilford)
         Status: In Progress

** Affects: python-os-brick (Ubuntu Hirsute)
     Importance: Undecided
         Status: Fix Released

** Affects: python-os-brick (Ubuntu Impish)
     Importance: Undecided
         Status: Fix Released

** Affects: python-os-brick (Ubuntu Jammy)
     Importance: Undecided
         Status: Fix Released


** Tags: attach in-stable-train in-stable-ussuri iscsi multipath seg sts sts-sponsor volume
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[SRU] iSCSI+Multipath: Volume attachment hungs if sessiong scanning fails
https://bugs.launchpad.net/bugs/1915678
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