iSCSI single path attach fails on slow WWN sysfs population

[Gorka Eguileor]

Under some circumstances we fail to attach a single pathed device but succeed if we do it multipathed.

We see the following error:

  2019-06-27 09:51:56.295 24133 ERROR cinder os_brick.exception.VolumeDeviceNotFound: Volume device not found at .

The reason for the failure is that even when the device is attached we cannot find the WWN on the sysfs in time, as the following 2 log entries show:

  2019-06-27 09:50:27.815 24133 DEBUG os_brick.initiator.connectors.iscsi [req-f91f00b2-3267-4aaa-b603-b46bb2c4f6e7 cinderlib cinderlib - - -] Connected to sdb using {'target_portal': 'w.x.y.z:3260', 'target_iqn': 'iqn.2000-05.com.3pardata:something', 'target_lun': 0, 'target_discovered': True, 'encrypted': False} _connect_vol /home/geguileo/code/rh/python-os-brick/os_brick/initiator/connectors/iscsi.py:664
  2019-06-27 09:50:37.831 24133 DEBUG os_brick.initiator.connectors.iscsi [req-f91f00b2-3267-4aaa-b603-b46bb2c4f6e7 cinderlib cinderlib - - -] Could not find the WWN for sdb. _connect_single_volume /home/geguileo/code/rh/python-os-brick/os_brick/initiator/connectors/iscsi.py:574

The reason why this doesn't fail when using multipath is because it is more tolerant and will not fail in this case. It will just return an empty string:
  2019-06-27 09:27:35.445 19066 WARNING os_brick.initiator.connectors.iscsi [req-4b06802d-50a2-4d88-b47c-231d6433e2d3 cinderlib cinderlib - - -] No dm was created, connection to volume is probably bad and will perform poorly.
  2019-06-27 09:27:35.447 19066 DEBUG os_brick.initiator.connectors.iscsi [req-4b06802d-50a2-4d88-b47c-231d6433e2d3 cinderlib cinderlib - - -] <== connect_volume: return (16066ms) {'type': 'block', 'scsi_wwn': '', 'path': '/dev/sdc'} trace_logging_wrapper /home/geguileo/code/rh/python-os-brick/os_brick/utils.py:170

(The path is not a multipath DM because multipathd didn't see the WWN yet either, so it couldn't form the DM yet).

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/667830

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/667830
Committed: https://git.openstack.org/cgit/openstack/os-brick/commit/?id=1c07f221f22f9ce6e2604efb9ce3ac30a42ff38c
Submitter: Zuul
Branch: master

commit 1c07f221f22f9ce6e2604efb9ce3ac30a42ff38c
Author: Gorka Eguileor <email address hidden>
Date: Thu Jun 27 11:19:15 2019 +0200

    iSCSI single path: Don't fail if there's no WWN

    This patch relaxes the single-pathed connections and allows them to
    complete even when we cannot detect the WWN on the sysfs, just like
    multipath connections do.

    Closes-Bug: #1834443
    Change-Id: Iae5a304329a2b172bc6b7f310623fad18956ae45

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/os-brick 2.10.0 release.