I have discovered that sometimes when migrating a VM, the migration itself will
succeed, but the migrate_from call on the target node will fail, as apparently
the status hasn't settled down yet. This is more likely to happen when
stopping pacemaker on a node, causing all its VMs to migrate away. Migration
succeeds, but then (sometimes) the status call in migrate_from fails, and the
VM is unnecessarily stopped and started. Note that it is NOT a timeout
problem, as the migrate_from operation (which only checks status) takes less
than a second.
I noticed the VirtualDomain RA does a loop rather than just checking the status
once as the Xen RA does, so I patched a similar thing into the Xen RA, and that
solved my problem. I don't know what the appropriate time to wait is, so I
copied the "2/3 of the timeout" logic from the stop function. Perhaps the full
timeout would be more appropriate?
Patch:
--- Xen.orig 2011-08-11 12:54:13.574795799 -0500
+++ Xen 2011-08-11 15:18:58.352851276 -0500
@@ -384,6 +384,20 @@
}
Xen_Migrate_From() {
+ if [ -n "$OCF_RESKEY_CRM_meta_timeout" ]; then
+ # Allow 2/3 of the action timeout for status to stabilize
+ # (The origin unit is ms, hence the conversion)
+ timeout=$((OCF_RESKEY_CRM_meta_timeout/1500))
+ else
+ timeout=10 # should be plenty
+ fi
+
+ while ! Xen_Status ${DOMAIN_NAME} && [ $timeout -gt 0 ]; do
+ ocf_log debug "$DOMAIN_NAME: Not yet active locally, waiting (timeout:
${timeout}s)"
+ timeout=$((timeout-1))
+ sleep 1
+ done
+
if Xen_Status ${DOMAIN_NAME}; then
Xen_Adjust_Memory 0
ocf_log info "$DOMAIN_NAME: Active locally, migration successful"
=== end patch ===
Example resource definition:
primitive vm-build11 ocf:heartbeat:Xen \
params xmfile="/mnt/xen/vm/build11" \
meta allow-migrate="true" target-role="Started" is-managed="true" \
utilization cores="1" mem="512" \
op start interval="0" timeout="60" \
op stop interval="0" timeout="60" \
op migrate_to interval="0" timeout="180" \
op monitor interval="30" timeout="30" start-delay="60"
Debug log excerpts (grep build11):
source node (app-02)
====
Aug 11 12:08:33 app-02 lrmd: [9952]: debug: on_msg_perform_op: add an operation
operation migrate_to[50] on ocf::Xen::vm-build11 for client 9955, its
parameters: CRM_meta_migrate_source=[app-02] CRM_meta_migrate_target=[app-04]
CRM_meta_record_pending=[false] CRM_meta_name=[migrate_to]
CRM_meta_timeout=[180000] crm_feature_set=[3.0.5] xmfile=[/mnt/xen/vm/build11]
to the operation list.
Aug 11 12:08:33 app-02 lrmd: [9952]: info: rsc:vm-build11:50: migrate_to
Aug 11 12:08:33 app-02 crmd: [9955]: info: process_lrm_event: LRM operation
vm-build11_monitor_30000 (call=49, status=1, cib-update=0, confirmed=true)
Cancelled
Aug 11 12:08:33 app-02 Xen[29909]: [29984]: INFO: build11: Starting xm migrate
to app-04
Aug 11 12:08:43 app-02 Xen[29909]: [30228]: INFO: build11: xm migrate to app-04
succeeded.
Aug 11 12:08:43 app-02 lrmd: [9952]: info: Managed vm-build11:migrate_to
process 29909 exited with return code 0.
Aug 11 12:08:43 app-02 crmd: [9955]: debug: create_operation_update:
do_update_resource: Updating resouce vm-build11 after complete migrate_to op
(interval=0)
Aug 11 12:08:43 app-02 crmd: [9955]: info: process_lrm_event: LRM operation
vm-build11_migrate_to_0 (call=50, rc=0, cib-update=75, confirmed=true) ok
Aug 11 12:08:43 app-02 crmd: [9955]: info: do_lrm_rsc_op: Performing
key=141:69:0:478c5322-daa4-462a-a333-6d26288fa416 op=vm-build11_stop_0 )
Aug 11 12:08:43 app-02 lrmd: [9952]: debug: on_msg_perform_op: add an operation
operation stop[52] on ocf::Xen::vm-build11 for client 9955, its parameters:
crm_feature_set=[3.0.5] to the operation list.
Aug 11 12:08:43 app-02 lrmd: [9952]: info: rsc:vm-build11:52: stop
Aug 11 12:08:44 app-02 Xen[30381]: [30469]: INFO: Xen domain build11 already
stopped.
Aug 11 12:08:44 app-02 lrmd: [9952]: info: RA output: (vm-build11:stop:stderr)
Error:
Aug 11 12:08:44 app-02 lrmd: [9952]: info: RA output: (vm-build11:stop:stderr)
Aug 11 12:08:44 app-02 lrmd: [9952]: info: RA output: (vm-build11:stop:stderr)
Domain 'build11' does not exist.
Aug 11 12:08:44 app-02 lrmd: [9952]: info: RA output: (vm-build11:stop:stderr)
Aug 11 12:08:44 app-02 lrmd: [9952]: info: Managed vm-build11:stop process
30381 exited with return code 0.
Aug 11 12:08:44 app-02 crmd: [9955]: debug: create_operation_update:
do_update_resource: Updating resouce vm-build11 after complete stop op
(interval=0)
Aug 11 12:08:44 app-02 crmd: [9955]: info: process_lrm_event: LRM operation
vm-build11_stop_0 (call=52, rc=0, cib-update=78, confirmed=true) ok
====
(I'm guessing the "already stopped" after migrate_to succeeds is not a problem.)
target node (app-04):
====
Aug 11 12:08:43 app-04 crmd: [9943]: info: do_lrm_rsc_op: Performing
key=200:68:0:478c5322-daa4-462a-a333-6d26288fa416 op=vm-build11_migrate_from_0 )
Aug 11 12:08:43 app-04 lrmd: [9940]: info: rsc:vm-build11:88: migrate_from
Aug 11 12:08:43 app-04 Xen[1574]: [1619]: ERROR: build11: Not active locally,
migration failed!
Aug 11 12:08:43 app-04 crmd: [9943]: info: process_lrm_event: LRM operation
vm-build11_migrate_from_0 (call=88, rc=1, cib-update=144, confirmed=true)
unknown error
Aug 11 12:08:43 app-04 crmd: [9943]: info: do_lrm_rsc_op: Performing
key=16:69:0:478c5322-daa4-462a-a333-6d26288fa416 op=vm-build11_stop_0 )
Aug 11 12:08:43 app-04 lrmd: [9940]: info: rsc:vm-build11:89: stop
Aug 11 12:08:44 app-04 Xen[1744]: [1852]: INFO: Xen domain build11 will be
stopped (timeout: 20s)
Aug 11 12:08:51 app-04 Xen[1744]: [2146]: INFO: Xen domain build11 stopped.
Aug 11 12:08:51 app-04 crmd: [9943]: info: process_lrm_event: LRM operation
vm-build11_stop_0 (call=89, rc=0, cib-update=145, confirmed=true) ok
Aug 11 12:09:06 app-04 crmd: [9943]: info: do_lrm_rsc_op: Performing
key=142:69:0:478c5322-daa4-462a-a333-6d26288fa416 op=vm-build11_start_0 )
Aug 11 12:09:06 app-04 lrmd: [9940]: info: rsc:vm-build11:91: start
Aug 11 12:09:10 app-04 lrmd: [9940]: info: RA output: (vm-build11:start:stdout)
Using config file "/mnt/xen/vm/build11".#012Started domain build11 (id=18)
Aug 11 12:09:11 app-04 crmd: [9943]: info: process_lrm_event: LRM operation
vm-build11_start_0 (call=91, rc=0, cib-update=147, confirmed=true) ok
Aug 11 12:09:11 app-04 crmd: [9943]: info: do_lrm_rsc_op: Performing
key=143:69:0:478c5322-daa4-462a-a333-6d26288fa416 op=vm-build11_monitor_30000 )
Aug 11 12:10:11 app-04 lrmd: [9940]: info: rsc:vm-build11:93: monitor
Aug 11 12:10:11 app-04 crmd: [9943]: info: process_lrm_event: LRM operation
vm-build11_monitor_30000 (call=93, rc=0, cib-update=149, confirmed=false) ok
====
Note the "Not active locally, migration failed!" error and subsequent
stop/start.
Aside: why is the stop timeout 20 sec? Looking at the Xen RA man page and
source, it seems like it should use the shutdown_timeout parameter, or it that
is not set, 2/3 of the stop timeout. I don't have shutdown_timeout set for
this resource, and the stop timeout is 60, but somehow it's getting 20 instead
of 40.
With my patch in place, everything is fine after a couple seconds:
(app-02 is the migration target in this case)
====
Aug 11 15:50:08 app-02 lrmd: [22253]: debug: on_msg_perform_op: add an
operation operation migrate_from[40] on ocf::Xen::vm-build11 for client 22256,
its parameters: CRM_meta_migrate_source=[app-04]
CRM_meta_migrate_target=[app-02] CRM_meta_record_pending=[false]
CRM_meta_timeout=[30000] crm_feature_set=[3.0.5] xmfile=[/mnt/xen/vm/build11]
to the operation list.
Aug 11 15:50:08 app-02 Xen[24984]: [25055]: DEBUG: build11: Not yet active
locally, waiting (timeout: 20s)
Aug 11 15:50:09 app-02 Xen[24984]: [25163]: INFO: build11: Active locally,
migration successful
====
Incidentally, on a test where I stopped pacemaker on a node running 5 VMs, only
one of them required this wait; the other four immediately returned "Active
locally, migration successful". It's a race condition mitigated by the wait
loop, I guess.
Software is SLES 11 HAE SP1 + latest updates (Xen RA belongs to
resource-agents-1.0.3-0.10.1).
Thanks,
Andrew Daugherity
Systems Analyst
Division of Research, Texas A&M University
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