1305589 – RFE: Request for warning if multipathd is not running/active

RHEL Engineering is moving the tracking of its product development work on RHEL 6 through RHEL 9 to Red Hat Jira (issues.redhat.com). If you're a Red Hat customer, please continue to file support cases via the Red Hat customer portal. If you're not, please head to the "RHEL project" in Red Hat Jira and file new tickets here. Individual Bugzilla bugs in the statuses "NEW", "ASSIGNED", and "POST" are being migrated throughout September 2023. Bugs of Red Hat partners with an assigned Engineering Partner Manager (EPM) are migrated in late September as per pre-agreed dates. Bugs against components "kernel", "kernel-rt", and "kpatch" are only migrated if still in "NEW" or "ASSIGNED". If you cannot log in to RH Jira, please consult article #7032570. That failing, please send an e-mail to the RH Jira admins at rh-issues@redhat.com to troubleshoot your issue as a user management inquiry. The email creates a ServiceNow ticket with Red Hat. Individual Bugzilla bugs that are migrated will be moved to status "CLOSED", resolution "MIGRATED", and set with "MigratedToJIRA" in "Keywords". The link to the successor Jira issue will be found under "Links", have a little "two-footprint" icon next to it, and direct you to the "RHEL project" in Red Hat Jira (issue links are of type "https://issues.redhat.com/browse/RHEL-XXXX", where "X" is a digit). This same link will be available in a blue banner at the top of the page informing you that that bug has been migrated.

Bug 1305589 - RFE: Request for warning if multipathd is not running/active

Summary: RFE: Request for warning if multipathd is not running/active

Keywords:
Status:	CLOSED ERRATA
Alias:	None
Product:	Red Hat Enterprise Linux 6
Classification:	Red Hat
Component:	device-mapper-multipath
Sub Component:
Version:	6.7
Hardware:	x86_64
OS:	Linux
Priority:	medium
Severity:	low
Target Milestone:	rc
Target Release:	---
Assignee:	Ben Marzinski
QA Contact:	Lin Li
Docs Contact:	Milan Navratil
URL:
Whiteboard:
Depends On:
Blocks:	1269194 1324930 1359510
TreeView+	depends on / blocked

Reported:	2016-02-08 16:10 UTC by John Pittman
Modified:	2020-09-10 09:32 UTC (History)
CC List:	15 users (show)
Fixed In Version:	device-mapper-multipath-0.4.9-94.el6
Doc Type:	Release Note
Doc Text:	Users are now warned if they create multipath devices while multipathd is not running With this update, multipath prints a warning message for adding and listing multipath devices when the multipathd service is not running.
Clone Of:
Clones:	1359510 (view as bug list)
Environment:
Last Closed:	2017-03-21 10:49:00 UTC
Target Upstream Version:
Embargoed:

Attachments	(Terms of Use)
Proposed Patch v1 (3.11 KB, patch) 2016-07-24 13:19 UTC, Milan P. Gandhi	no flags	Details \| Diff
View All

Links
System	ID	Private	Priority	Status	Summary	Last Updated
Red Hat Knowledge Base (Solution)	2139121	0	None	None	None	2016-02-11 02:30:40 UTC
Red Hat Product Errata	RHBA-2017:0697	0	normal	SHIPPED_LIVE	device-mapper-multipath bug fix and enhancement update	2017-03-21 12:39:06 UTC

Description John Pittman 2016-02-08 16:10:52 UTC

Description of problem:

Opening at customer request.  Is it possible to get a warning if the dm_multipath module is loaded, multipath devices are present, but multipathd is not set to on?  Perhaps when using the 'multipath' command.  The idea is that most users never use the multipathd command; they configure multipathing and use the multipath command. 

The multipathd service is an integral part of multipathing, so we should at least give an informative message if it is not running and the system is using multipath.

Why do we not auto-start multipathd if the module is in use?  Are there use cases where we would want to have multipath devices, but not use multipathd?  I have seen many cases where proper failover/mapping was not acheived because multipathd was not running and no one knew.  Could we request an auto load for multipathd instead of the warning?  Maybe both?  

Thanks for your time.  Please let me know if I can be of any help.

Version-Release number of selected component (if applicable):

device-mapper-multipath-0.4.9-87.el6.x86_64

Expected Results:

- multipathd service autostart with module load
- warning if service is not running when using multipath command

Comment 1 Ben Marzinski 2016-02-08 20:04:02 UTC

Loading the module can't autostart the service. There's no hook for anything like that in the module code. Besides, if there are no multipath devices, we don't want to start the service.  If the service is enabled in systemd, it will autostart on boot, as long a /etc/multipath.conf exists.  Creating the configuration file the recommended way, with

# mpathconf --enable

does enable the service in systemd. However, it does not autostart the service at that point.  This is because users often want to actually edit the configuration file before starting the service the first time. The service will autostart on the next reboot.

There are two ways to actually create multipath devices. Either multipathd will automatically create them, or they can be created manually by running multipath.  I can make multipath print a warning message if multipathd isn't running. This should solve the case where there are multipath devices but multipathd isn't running.

Does this sound reasonable?

Comment 2 John Pittman 2016-02-08 20:12:22 UTC

Yes Ben that sounds perfect.
Thanks a lot.

John

Comment 3 Milan P. Gandhi 2016-07-24 13:19:40 UTC

Created attachment 1183368 [details]
Proposed Patch v1

With the attached patch, dm-multipath commands e.g. multipath -v2, multipath -ll etc. now checks if there are multipath device maps created, and multipathd service is running or not?

If the multipath device maps are created, but multipathd service is not running, then in such case there will be a warning message displayed to inform the user that IO failover/failback may not work as expected without multipathd process running.

Comment 4 Milan P. Gandhi 2016-07-24 13:27:42 UTC

Hello,

The attached patch is for dm-multipath package in RHEL 7.
There are significant differences in dm-multipath in RHEL 6 and 7 about how to verify if the multipathd process is running or not. So this patch would not be applicable for RHEL 6 dm-multipath package. I have cloned the RHEL 7 BZ#1359510 from current BZ, and have attached this patch in BZ#1359510.

Sorry for the noise.

Many thanks,
Milan.

Comment 7 Ben Marzinski 2016-10-15 18:20:17 UTC

Thanks for the patch. Applied (in a slightly modified form).

Comment 10 Lin Li 2017-01-09 03:12:03 UTC

Reproduced on device-mapper-multipath-0.4.9-72.el6
1. [root@storageqe-71 ~]# rpm -qa | grep multipath
device-mapper-multipath-libs-0.4.9-72.el6.x86_64
device-mapper-multipath-0.4.9-72.el6.x86_64

2. [root@storageqe-71 ~]# mpathconf --enable 
3. [root@storageqe-71 ~]# service multipathd restart
ok
Stopping multipathd daemon: [  OK  ]
Starting multipathd daemon: [  OK  ]

4. [root@storageqe-71 ~]# service multipathd stop
Stopping multipathd daemon: [  OK  ]

5. [root@storageqe-71 ~]# multipath -ll
mpathb (3600140515efaacbb9854dbf91428aa0d) dm-3 LIO-ORG,IBLOCK
size=10G features='0' hwhandler='0' wp=rw
|-+- policy='round-robin 0' prio=1 status=active
| `- 1:0:0:1 sdd 8:48 active ready running
`-+- policy='round-robin 0' prio=1 status=enabled
  `- 0:0:0:1 sdb 8:16 active ready running
mpatha (36001405cca4c176848d4482853c9962c) dm-4 LIO-ORG,IBLOCK
size=50G features='0' hwhandler='0' wp=rw
|-+- policy='round-robin 0' prio=1 status=active
| `- 0:0:0:0 sda 8:0  active ready running
`-+- policy='round-robin 0' prio=1 status=enabled
  `- 1:0:0:0 sdc 8:32 active ready running
<----------------List multipath devices while multipathd is stopped, multipath doesn't  print a warning message



Verified on device-mapper-multipath-0.4.9-100.el6
1. [root@storageqe-71 ~]# rpm -qa | grep multipath
device-mapper-multipath-debuginfo-0.4.9-100.el6.x86_64
device-mapper-multipath-0.4.9-100.el6.x86_64
device-mapper-multipath-libs-0.4.9-100.el6.x86_64

2. [root@storageqe-71 ~]# mpathconf --enable
3. [root@storageqe-71 ~]# service multipathd restart
ux_socket_connect: No such file or directory
Stopping multipathd daemon: [FAILED]
Starting multipathd daemon: [  OK  ]

4. [root@storageqe-71 ~]# multipath -ll
mpathb (3600140515efaacbb9854dbf91428aa0d) dm-3 LIO-ORG,IBLOCK
size=10G features='0' hwhandler='0' wp=rw
|-+- policy='round-robin 0' prio=1 status=active
| `- 0:0:0:1 sdb 8:16 active ready running
`-+- policy='round-robin 0' prio=1 status=enabled
  `- 1:0:0:1 sdc 8:32 active ready running
mpatha (36001405cca4c176848d4482853c9962c) dm-4 LIO-ORG,IBLOCK
size=50G features='0' hwhandler='0' wp=rw
|-+- policy='round-robin 0' prio=1 status=active
| `- 0:0:0:0 sda 8:0  active ready running
`-+- policy='round-robin 0' prio=1 status=enabled
  `- 1:0:0:0 sdd 8:48 active ready running

5. [root@storageqe-71 ~]# service multipathd stop
Stopping multipathd daemon: [  OK  ]

6. [root@storageqe-71 ~]# multipath -ll
mpathb (3600140515efaacbb9854dbf91428aa0d) dm-3 LIO-ORG,IBLOCK
size=10G features='0' hwhandler='0' wp=rw
|-+- policy='round-robin 0' prio=1 status=active
| `- 0:0:0:1 sdb 8:16 active ready running
`-+- policy='round-robin 0' prio=1 status=enabled
  `- 1:0:0:1 sdc 8:32 active ready running
mpatha (36001405cca4c176848d4482853c9962c) dm-4 LIO-ORG,IBLOCK
size=50G features='0' hwhandler='0' wp=rw
|-+- policy='round-robin 0' prio=1 status=active
| `- 0:0:0:0 sda 8:0  active ready running
`-+- policy='round-robin 0' prio=1 status=enabled
  `- 1:0:0:0 sdd 8:48 active ready running

multipath device maps are present, but 'multipathd' service is not running
IO failover/failback will not work without 'multipathd' service running   

<----------------List multipath devices while multipathd is stopped, multipath  prints a warning message now.



Test result: list or create multipath devices while multipathd is stopped.  Multipath should now print a warning message, where before it wouldn't

Comment 14 errata-xmlrpc 2017-03-21 10:49:00 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2017-0697.html

Note You need to log in before you can comment on or make changes to this bug.