Hi Praveen
I have also looked at this and have seen much the same as Vu already has
pointed out. There is also another problem and I hope I manage to explain in an
understandable way. Let's say that both active (Aa) and standby (Sb) are acting
as appliers (only A will send notifications). Then both appliers will receive
the IMM info and execute the CCB callbacks. However, they will not get the
information at the same time. It is also not known which applier that gets the
information first. This means that it is possible that when a state change
happens the new active will get the apply callback for the same change
information that the previous active has already got and sent a notification
for. Let’s say we improve by only letting the active run as an applier but we
still end up with a synchronization problem.
It is probably ok to use RDE callback to know when HA state is changed instead
of having NTF terminate imcn as before. It is no big concern if a monitored IMM
change happen without imcn sending a notification e.g. during restart as long
as a "may have missed notifications" notification is sent.
A solution could be to not change role when a state change happen instead RDE
callback handling could run in a separate thread in the imcn process and
immediately when a state change is detected exit the imcn process. This will be
detected by the imcn monitoring in NTF that will restart the imcn process.
Sending a "may have missed notifications" notification at start up can be done
as is. Imcn could detect its role by checking with RDE as in your patch and in
this case information does not have to be provided by NTF.
I will also come back with a suggestion for how to install your patch in a bit
"cleaner" way. I will do some modifications of the patch to explain what I mean.
Thanks
Lennart
---
** [tickets:#2219] ntfd: circular dependency with osafntfimcnd**
**Status:** assigned
**Milestone:** 5.0.2
**Created:** Thu Dec 08, 2016 05:14 AM UTC by Gary Lee
**Last Updated:** Thu Dec 15, 2016 03:28 AM UTC
**Owner:** Praveen
A circular dependency can be seen when performing a si-swap of
safSi=SC-2N,safApp=OpenSAF:
1. Active NTFD is trying to sync with Standby using MBC
2. Standby NTFD is the process of terminating its local osafntfimcnd. It is
stuck in timedwait_imcn_exit() and cannot reply to the Active.
3. osafntfimcnd [on standby] is trying to send a notfication to Active NTFD
So we have (1) depending on (2) depending on (3) depending on (1)
This results in a temporary deadlock that dramatically slows down NTFD's
ability to process its main dispatch loop. The deadlock only lasts for approx.
1 second, when mbcsv_mds_send_msg() times out. But since there could be lots of
MBC messages to send, sometimes osafntfimcnd is killed with SIGABRT generating
a coredump. The si-swap operation will also timeout.
steps to reproduce
- Run loop of ntftest 32
root@SC-1:~# for i in {1..10}; do ntftest 32; done
- On another terminal, keep swapping 2N Opensaf SI, got coredump after couples
of swaps
root@SC-1:~# amf-adm si-swap safSi=SC-2N,safApp=OpenSAF
...
root@SC-1:~# amf-adm si-swap safSi=SC-2N,safApp=OpenSAF
~~~
SC-2 (active)
There are a lot of send failures. Each taking approx. 1 second to timeout.
During these 1 second timeouts, NTFD cannot process the main dispatch loop.
Dec 7 11:01:37.531772 osafntfd [452:mbcsv_mds.c:0185] >>
mbcsv_mds_send_msg: sending to vdest:e
Dec 7 11:01:37.531781 osafntfd [452:mbcsv_mds.c:0209] TR send type
MDS_SENDTYPE_REDRSP:
Dec 7 11:01:38.537307 osafntfd [452:mbcsv_mds.c:0247] <<
mbcsv_mds_send_msg: failure
Dec 7 11:01:38.537758 osafntfd [452:mbcsv_mds.c:0185] >>
mbcsv_mds_send_msg: sending to vdest:e
Dec 7 11:01:38.537766 osafntfd [452:mbcsv_mds.c:0209] TR send type
MDS_SENDTYPE_REDRSP:
Dec 7 11:01:39.543180 osafntfd [452:mbcsv_mds.c:0247] <<
mbcsv_mds_send_msg: failure
Dec 7 11:01:39.543695 osafntfd [452:mbcsv_mds.c:0185] >>
mbcsv_mds_send_msg: sending to vdest:e
Dec 7 11:01:39.543698 osafntfd [452:mbcsv_mds.c:0209] TR send type
MDS_SENDTYPE_REDRSP:
Dec 7 11:01:40.545252 osafntfd [452:mbcsv_mds.c:0247] <<
mbcsv_mds_send_msg: failure
Dec 7 11:01:40.545719 osafntfd [452:mbcsv_mds.c:0185] >>
mbcsv_mds_send_msg: sending to vdest:e
Dec 7 11:01:40.545726 osafntfd [452:mbcsv_mds.c:0209] TR send type
MDS_SENDTYPE_REDRSP:
Dec 7 11:01:41.551328 osafntfd [452:mbcsv_mds.c:0247] <<
mbcsv_mds_send_msg: failure
Dec 7 11:01:41.551971 osafntfd [452:mbcsv_mds.c:0185] >>
mbcsv_mds_send_msg: sending to vdest:e
Dec 7 11:01:41.551979 osafntfd [452:mbcsv_mds.c:0209] TR send type
MDS_SENDTYPE_REDRSP:
Dec 7 11:01:42.557594 osafntfd [452:mbcsv_mds.c:0247] <<
mbcsv_mds_send_msg: failure
Dec 7 11:01:42.558171 osafntfd [452:mbcsv_mds.c:0185] >>
mbcsv_mds_send_msg: sending to vdest:e
Dec 7 11:01:42.558179 osafntfd [452:mbcsv_mds.c:0209] TR send type
MDS_SENDTYPE_REDRSP:
Dec 7 11:01:43.564051 osafntfd [452:mbcsv_mds.c:0247] <<
mbcsv_mds_send_msg: failure
Dec 7 11:01:43.564874 osafntfd [452:mbcsv_mds.c:0185] >>
mbcsv_mds_send_msg: sending to vdest:e
Dec 7 11:01:43.564883 osafntfd [452:mbcsv_mds.c:0209] TR send type
MDS_SENDTYPE_REDRSP:
Dec 7 11:01:44.572407 osafntfd [452:mbcsv_mds.c:0247] <<
mbcsv_mds_send_msg: failure
Dec 7 11:01:44.573262 osafntfd [452:mbcsv_mds.c:0185] >>
mbcsv_mds_send_msg: sending to vdest:e
Dec 7 11:01:44.573271 osafntfd [452:mbcsv_mds.c:0209] TR send type
MDS_SENDTYPE_REDRSP:
Dec 7 11:01:45.575091 osafntfd [452:mbcsv_mds.c:0247] <<
mbcsv_mds_send_msg: failure
Dec 7 11:01:47.083548 osafntfd [452:mbcsv_mds.c:0185] >>
mbcsv_mds_send_msg: sending to vdest:e
~~~
~~~
SC-1 (standby)
NTFD is trying to terminate osafntfimcnd. While it is doing that, it cannot
reply to NTFD on SC-2. Meanwhile, osafntfimcnd is sending NTF notifications to
NTFD on SC-1.
Dec 7 11:01:35.453151 osafntfd [464:ntfs_imcnutil.c:0316] TR
handle_state_ntfimcn: Terminating osafntfimcnd process
Dec 7 11:01:45.474313 osafntfd [464:ntfs_imcnutil.c:0124] TR Termination
timeout
Dec 7 11:01:45.474375 osafntfd [464:ntfs_imcnutil.c:0130] <<
wait_imcnproc_termination: rc = -1, retry_cnt = 101
Dec 7 11:01:45.474387 osafntfd [464:ntfs_imcnutil.c:0168] TR Normal
termination failed. Escalate to abort
Dec 7 11:01:45.574703 osafntfd [464:ntfs_imcnutil.c:0172] TR Imcn
successfully aborted
Dec 7 11:01:45.574712 osafntfd [464:ntfs_imcnutil.c:0187] <<
timedwait_imcn_exit
~~~
---
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