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Udev events can come in like a flood when something changes. It really
doesn't do us any good to refresh the state of the service numerous times
when 1 would suffice. We had something like this before, but it was
removed when we added the refresh thread. However, we have since learned
that we need to sequence events in the correct order and block dbus
operations if we believe the state has been affected, thus udev events are
being processed on the main work queue. This change limits spurious
work items from getting to the queue.
If we always disable the sending of notify dbus events then in the case
where all the users are lvm dbus users we will be in udev handling mode
until at least 1 external lvm command occurs. Instead we will not disable
notify dbus until after we get at least 1 external event. This makes the
service get into the correct mode of operation faster.
Utilizing the --config option we will utilize global/notify_dbus=0 so
that the service itself doesn't generate change events which it then needs to
process.
We need to place query operations in the queue to prevent the case where
a client knows of something before the service does. For example if a
client creates a PV/VG/LV outside of the dbus API and then immediately
tries to lookup and use that resource in the lvm dbus service it should
be present. By placing the queries in the work queue any previous
refresh operation will complete before we process the query.
The function timeout_add_seconds has quite a bit of variability. Using
timeout_add which specifies the timeout in ms instead of seconds. Testing
shows that this is much more consistent which should improve clients that
are using shorter timeouts for the API and the connection.
Added a properties changed signal on the job dbus object so that client
can wait for a signal that the job is complete instead of polling or
blocking on the wait method.
Allows the user to override the number of commands that get dumped
to the log when we encounter a lvm error. Also useful during
development when you don't want to see the blackbox output.
When reading data from stdout & stderr we were reading until the
reading until we got None back which really isn't needed as the
read will return everything that is available.
We need to acquire a lock which can block us which in turn causes
the dbus request handling to block as well. Place the request on
the work queue instead.
Our expectation was that when using the lvm shell that when the lvm prompt
was read from stdout, that all other ouput had been written and flushed.
However, this doesn't appear to be the case. Add extra read passes to
retrieve delayed report data.
In preparation to have more than one thread issuing commands to lvm
at the same time we need to serialize updates to the dbus state and
retrieving the global lvm state. To achieve this we have one thread
handling this with a thread safe queue taking and coalescing requests.
This code is no longer needed because the back ground task has been
removed. Will add back if we change the design and end up utilizing
multiple worker threads.
There is no reason to create another background task when the task that
created it is going to block waiting for it to finish. Instead we will
just execute the logic in the worker thread that is servicing the worker
queue.
Instead of creating a thread to handle the case where a client
is calling job.Wait, we will utilize a timer. This significantly
reduces the number of threads that get created and destroyed while
the service is running.
We will fetch the lvm state in non-main thread and only process the new
data with the main thread to prevent hanging the main thread event loop.
ref. https://bugs.freedesktop.org/show_bug.cgi?id=98521
The following LvCommon properties were added so that the API
would have the same functionality as lvm2app has.
LvCommon.MetaDataSizeBytes
LvCommon.Attr
LvCommon.MetaDataPercent
LvCommon.CopyPercent
LvCommon.SnapPercent
LvCommon.SyncPercent
When a PV device is missing lvm will return '[unknown]' for the device
path. The object manager keeps a hash table lookup for uuid and for PV's
device name. When we had multiple PVs with the same device path we
we only had 1 key in the table for the lvm id (device path). This caused
a problem when the PV device transitioned from '[unknown]' to known as any
subsequent transitions would cause an exception:
Traceback (most recent call last):
File "/usr/lib/python3.5/site-packages/lvmdbusd/request.py", line 66, in run_cmd
result = self.method(*self.arguments)
File "/usr/lib/python3.5/site-packages/lvmdbusd/manager.py", line 205, in _pv_scan
cfg.load()
File "/usr/lib/python3.5/site-packages/lvmdbusd/fetch.py", line 24, in load
cache_refresh=False)[1]
File "/usr/lib/python3.5/site-packages/lvmdbusd/pv.py", line 48, in load_pvs
emit_signal, cache_refresh)
File "/usr/lib/python3.5/site-packages/lvmdbusd/loader.py", line 80, in common
cfg.om.remove_object(cfg.om.get_object_by_path(k), True)
File "/usr/lib/python3.5/site-packages/lvmdbusd/objectmanager.py", line 153, in remove_object
self._lookup_remove(path)
File "/usr/lib/python3.5/site-packages/lvmdbusd/objectmanager.py", line 97, in _lookup_remove
del self._id_to_object_path[lvm_id]
KeyError: '[unknown]'
when trying to delete a key that wasn't present. In this case we don't add a
lookup key for the device path and the PV can only be located by UUID.
Ref: https://bugzilla.redhat.com/show_bug.cgi?id=1379357
Gris debugged that when we don't have a method the introspection
data is missing the interface itself eg.
<interface name="<your_obj_iface_name>" />
When adding the properties to the dbus object introspection we will
add the interface too if it's missing. This now allows us the
ability to have a dbus object with only properties.
When we register a failure we need to use a valid value which will be
returned with the object manager. Otherwise we will raise an Exception
because we are trying to construct an object path from None.
The methods were returning an instance of the object instead of the
object path which was causing an exception when the result was returned
with the job object as we are explicity trying to return an object path.
Unit test added which re-creates the issue and verifies the fix.
- Prevent --lvmshell with --nojson, not a valid combination
- If user is preventing json, then no lvmshell usage
- Return boolean on Manager.UseLvmShell
The normal mode of operation will be to monitor for udev events until an
ExternalEvent occurs. In that case the service will disable monitoring
for udev events and use ExternalEvent exclusively.
Note: User specifies --udev the service will always monitor udev regardless
if ExternalEvent is being called too.
With the addition of JSON and the ability to get output which is known to
not contain any extraneous text we can now leverage lvm shell, so that we
don't fork and exec lvm command line repeatedly.
When we are running in a terminal it's useful to have a date & ts on log
output like you get when output goes to the journal. Check if we are
running on a tty and if we are, add it in.
When converting to a cache lv, tests were hanging with a prompt for
"Do you want wipe existing metadata of cache pool volume
To preserve cache metadata add option "--zero n".
WARNING: Reusing mismatched cache pool metadata MAY DESTROY YOUR DATA!"
This is new.
When a client is doing a wait on a job, any other clients will hang
when trying to do anything with the service. This is caused by
the wait code which was placing the thread that handles
incoming dbus requests to sleep until either the timeout expired or
the job operation completed.
This change creates a thread for the wait request, so that the thread
processing incoming requests can continue to run.
We call 'lvm help' to find out if fullreport is supported. Lvm
dumps help to stderr. Common code prints a warning if we exit
with 0, but have something in stderr so we are skipping the warning
message.
The following operations would hang if lvm was compiled with
'enable-notify-dbus' and the client specified -1 for the timeout:
* LV snapshot merge
* VG move
* LV move
This was caused because the implementation of these three dbus methods is
different. Most of the dbus method calls are executed by gathering information
needed to fulfill it, placing that information on a thread safe queue and
returning. The results later to be returned to the client with callbacks.
With this approach we can process an arbitrary number of commands without any
of them blocking other dbus commands. However, the 3 dbus methods listed
above did not utilize this functionality because they were implemented with a
separate thread that handles the fork & exec of lvm. This is done because these
operations can be very slow to complete. However, because of this the lvm
command that we were waiting on is trying to call back into the dbus service to
notify it that something changed. Because the code was blocking the process
that handles the incoming dbus activity the lvm command blocked. We were stuck
until the client timed-out the connection, which then causes the service to
unblock and continue. If the client did not have a timeout, we would have been
hung indefinitely.
The fix is to always utilize the worker queue on all dbus methods. We need to
ensure that lvm is tested with 'enable-notify-dbus' enabled and disabled.
