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Thin plugin started to use configuble setting to allow to configure
usage of external scripts - however to read this value it needed to
execute internal command as dmeventd itself has no access to lvm.conf
and the API for dmeventd plugin has been kept stable.
The call of command itself was not normally 'a big issue' until users
started to use higher number of monitored LVs and execution of command
got stuck because other monitored resource already started to execute
some other lvm2 command and become blocked waiting on VG lock.
This scenario revealed necesity to somehow avoid calling lvm2 command
during resource registration - but this requires bigger changes - so
meanwhile this patch tries to minimize the possibility to hit this race
by obtaining any configurable setting just once - such patch is small
and covers majority of problem - yet better solution needs to be
introduced likely with bigger rework of dmeventd.
TODO: Avoid blocking registration of resource with execution of lvm2
commands since those can get stuck waiting on mutexes.
Some minimal set of changes to make vdo plugin compilable in stable branch:
Use older headers.
Implement simple vdo status parser to only resolve use-percentage.
Introduce VDO plugin for monitoring VDO devices.
This plugin can be used also by other users, as plugin checks
for UUID prefix 'LVM-' and run lvm actions only on those
devices.
Non LVM- device are only monitored and log warnings
when usage threshold reaches 80%.
Commit a30e622279:
"scan: work around udev problems by avoiding open RDWR"
had us reopen a device RDWR in the write function. Since
we know earlier that the command intends to write to devices
in the VG, we can reopen the VG's devices RDWR during the
rescan instead of waiting until the writes to happen.
When the lvmlockd lock is shared, upgrade it to ex
when repair (writing) is needed during vg_read.
Pass the lockd state through additional read-related
functions so the instances of repair scattered through
vg_read can be handled.
(Temporary solution until the ad hoc repairs can be
pulled out of vg_read into a top level, centralized
repair function.)
The clvmd saved_vg data is independent from the normal lvm
lvmcache vginfo data, so separate saved_vg from vginfo.
Normal lvm doesn't need to use save_vg at all, and in clvmd,
lvmcache changes on vginfo can be made without worrying
about unwanted effects on saved_vg.
I don't like having this in a common header because it means you end
up including too much and causing unneccessary dependencies. eg,
lib/misc/lib.h includes libdevmapper.h, internationalisation, and
logging stuff.
There are likely more bits of code that can be removed,
e.g. lvm1/pool-specific bits of code that were identified
using FMT flags.
The vgconvert command can likely be reduced further.
The lvm1-specific config settings should probably have
some other fields set for proper deprecation.
Recent changes allow some major simplification of the way
lvmcache works and is used. lvmcache_label_scan is now
called in a controlled fashion at the start of commands,
and not via various unpredictable side effects. Remove
various calls to it from other places. lvmcache_label_scan
should not be called from anywhere during a command, because
it produces an incorrect representation of PVs with no MDAs,
and misclassifies them as orphans. This has been a long
standing problem. The invalid flag and rescanning based on
that is no longer used and removed. The 'force' variation is
no longer needed and removed.
We can't let clvmd keep all scanned devs open,
which prevents them from being removed. So
drop the bcache data (and close fds) affter
doing a label scan.
Also set up bcache before the clvm-specific
vg_read (which needs to rescan the vg's devs
using bcache) and destroy the bcache after.
Since this function is called with 'fd == -1', but Coverity can't see
this path can't be visited with this argument, add explicit check for
valid descriptor.
When dmeventd thin plugin forks a configurable script, switch to use
execvp to pass whole environment present to dmeventd - so all configured
paths present at dmeventd startup are visible to script.
This was likely not a problem for common user enviroment,
however in test suite case variable like LVM_SYSTEM_DIR were
not actually used from test itself but rather from
a system present lvm.conf and this may have cause strange
behavior of a testing script.
Avoid using same return code for reporting 2 different things
and stricly report error code by return value and add new
parameter for reporting monitoring status.
This makes easier to recognize which error we got from dm_event
and continue only with ENOENT.
lvmdbusd executable script must use python3 interpreter detected by
configure script, as site-packages directory used for library is only
used by that interpreter.
When sanlock or dlm lock managers return an error number
that we don't recognize, replace it with a generic -ELMERR
which is defined in the set of special lvmlockd error
numbers. Otherwise, an unknown lock manager error number
could be misinterpreted for something else if it happened
to overlap another set of error numbers (which they have
not thus far.)
These less common errors returned from sanlock should
also cause sanlock to retry the lock acquire:
- i/o timeout occurs during sanlock_acquire().
other i/o on the same disk as the leases can cause
sanlock i/o timeouts.
- low level disk paxos contention between hosts naturally
causes one host to not acquire the lease. There are a
couple special error numbers associated with these cases
that should just be recognized as a normal failure to
acquire the lease.
In HA cluster, we have "clvm" resource agent to manage clvmd daemon.
The agent invokes clvmd like: "clvmd -T90 -d0", which always prints
a scaring error message:
"""
local socket: connect failed: No such file or directory
"""
When specifed with "-d" option, clvmd tries to check if an instance
of the clvmd daemon is already running through a testing connection.
The connect() will fail with this ENOENT error in such case, so supress
the error message in such case.
TODO: add missing error reaction code - since ofter log_error, program
is not supposed to continue running (log_error() is for reporting
stopping problems).
Signed-off-by: Eric Ren <zren@suse.com>
When dmeventd receives SIGTERM/INT/HUP/QUIT it validates if exit is possible.
If there was any device still monitored, such exit request used to
be ignored/refused. This 'usually' worked reasonably well, however if there
is very short time period between last device is unmonitored and signal
reception - there was possibility such EXIT was ignored, as dmeventd has
not yet got into idle state even commands like 'vgchange -an' has already
finished.
This patch changes logic towards scheduling EXIT to the nearest
point when there is no monitored device.
EXIT is never forgotten.
NOTE: if there is only a single monitored device and someone sends
SIGTERM and later someone uses i.e. 'lvchange --refresh' after
unmonitoring dmeventd will exit and new instance needs to be
started.
If you send a SIGUSR1 (10) to the daemon it will dump all the
threads current stacks to stdout. This will be useful when the
daemon is apparently hung and not processing requests.
eg.
$ sudo kill -10 <daemon pid>
Make sure that any and all code that executes in the main thread is
wrapped with a try/except block to ensure that at the very least
we log when things are going wrong.
