Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: René Nussbaumer <rn@google.com>

This allows users of these classes to simply pass None if they want to use the
default value (the actual default is an internal constant), instead of
dynamically constructing the keyword arguments.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: René Nussbaumer <rn@google.com>

This was already outdated when the initial version of SharedLock was added
in commit 162c1c1f (February 2008).

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

For proper support of job priorities, jobs' locks need to respect
priorities.  Otherwise it could happen that a job with a lower priority
could get a lock before a job with a higher priority (depending on
timeouts and when they start acquiring).

This patch adds support for priorities in SharedLock and LockSet and
provides (unfortunately non-trivial) unittests. Outdated comments are also
adjusted and improved.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>

This is accomplished by keeping a list of waiting threads instead
of just their number inside the lock-internal condition. A few
other tweaks to the output format are also made.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

This patch adds an initial implementation of a lock monitor, accessible
for the user through “gnt-debug locks”. It currently shows all resource
locks: BGL, nodes and instances. Config and job queue locks could be
shown too, but wouldn't be of much help.  The current owner(s) and mode
are also shown.

Showing pending acquires will require further changes on the SharedLock
internals and is not yet implemented.

Example output:
$ gnt-debug locks -o name,mode,owner
Name            Mode      Owner
BGL/BGL         shared    JobQueue19/Job147
instances/inst1 exclusive JobQueue19/Job147
instances/inst2 -         -
instances/inst3 -         -
instances/inst4 -         -
nodes/node1     exclusive JobQueue19/Job147
nodes/node2     exclusive JobQueue19/Job147

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

This patch adds lock names to SharedLocks and LockSets, that can be used
later for displaying the actual locks being held/used in places where we
only have the lock, and not the entire context of the locking operation.

Since I realized that the production code doesn't call LockSet with the
proper members= syntax, but directly as positional parameters, I've
converted this (and the arguments to GlobalLockManager) into positional
arguments.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>

The ssynchronized decorator takes the lock to act on in input.
With this change we allow a string to be passed, and if so we assume the
function it protects is a class method, and we act on the member of the
class itself named as the string we got.

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

This class is unused and untested. We must have forgot it around.

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>

If a shared lock is used inside a condition, we need to make sure that
it's reacquired in the same way as it was originally, after the wait.

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>

utils.py, where they were before, is already huge.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>

While commit 413b7472 fixed the issue of poll(2) returning too
soon, it didn't work when the poll(2) call should've been
blocking. This is now fixed and verified.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

Iustin Pop noticed unusually high CPU usage with 2.1's master
daemon, even with very simple opcodes like OP_TEST_DELAY. As
it turns out, we inadvertently passed seconds as milliseconds
to a call to poll(2). Due to the way the loop around the call
works it didn't break competely, but caused higher CPU usage
by the poll(2) call returning too early.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

This patch missing @type information for all public methods, modifies
one to conform to the rest, and removes some information from @param
when it's been expressed in @type.

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

According to http://docs.python.org/reference/datamodel.html#slots



* The action of a __slots__ declaration is limited to the class where it
  is defined. As a result, subclasses will have a __dict__ unless they
  also define __slots__ (which must only contain names of any
  /additional/ slots).

* If a class defines a slot also defined in a base class, the instance
  variable defined by the base class slot is inaccessible (except by
  retrieving its descriptor directly from the base class). This renders
  the meaning of the program undefined. In the future, a check may be
  added to prevent this.

Signed-off-by: Balazs Lecz <leczb@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>
Signed-off-by: Iustin Pop <iustin@google.com>

This patch fixes a race condition when acquiring all locks in
a LockSet instance. The list of lock names needs to be sorted
to guarantee a consistent locking order, but the names were not
sorted when acquiring all locks in the set.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>

In case an exception was thrown while acquiring the lock, not necessarily all
owned locks are also really acquired. Before this change, an exception could be
masked by another exception thrown here. There is no good clean-up strategy
when acquiring a lock fails with an exception in either case.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

This patch should have only:

- pylint disables
- docstring changes
- whitespace changes

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Olivier Tharan <olive@google.com>

This removes/updates some module-wide pylint disables.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Olivier Tharan <olive@google.com>

This patch adds targeted pylint disables, where it makes sense (either
due to limitations in pylint or due to historical usage), and also a few
blanket ones in rapi where all the names are… “different”.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Olivier Tharan <olive@google.com>

This patch removes the quotes from CommaJoin and converts most of the
callers (that I could find) to it. Since CommaJoin does str(i) for i in
param, we can remove these, thus simplifying slightly a few calls.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

This class can also be used by mcpu.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>

By moving the main code of LockSet.acquire to its own function
we reduce the code complexity a bit and clarify the exception
handling.

This also fixes a case where a lock acquire timeout wasn't
handled correctly, leading to obscure error messages.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>

Found using pylint and epydoc.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>

The timeout passed to LockSet.acquire() is measured over all lock acquires. If
LockSet.acquire fails to acquire all requested locks within the specified
amount of time, all locks are released again and the acquire fails.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>

There were more race conditions. By adding a notify function to
SharedLock.acquire we can prevent them.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

With this patch we simplify usage on the SingleActionCondition (which
wasn't a condition at all) by making it a real condition. This way we
can just wait() on it, or notifyAll() as we would on a normal one. The
only catch is that notifyAll can be called only once, and wait can only
be called before notifyAll has, but luckily our PipeCondition, now quite
simplified, takes care of this, by providing a new SingleActionCondition
each time the previous one has been notified.

No Start/StopUsing function are needed anymore, and thus the condition
is a lot more robust, and there's no way file descriptors can be left
open, as they are closed in a finally block, in the same function where
they were opened, by the last thread exiting the class.

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>

Each condition has an underlying lock, the acquire and release methods,
and a few helper methods to check that it's called in the proper way.

Abstract them to a separate class so we can have more than one without
duplicating this code.

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>

SharedLock.__acquire_unlocked uses keyword parameters. Just passing
the timeout would set the “shared” parameter.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

Also remove the “blocking” parameter from LockSet.remove and
GanetiLockManager.remove. There's no point in implementing timeouts on removal
unless we need them.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>

_PipeCondition is a condition implemented using pipe(2) and poll(2).
It allows the implementation of timeouts without using a busy-wait loop
with time.sleep.

Unlike Python's built-in threading.Condition class and to save file
descriptors and an internal queue, it can only be used to notify
all waiters. Ganeti's use case for this condition class doesn't
require the ability to notify only one waiter.

Signed-off-by: Guido Trotter <ultrotter@google.com>
Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>

This class will be used as a basic block for pipe(2)-based
conditions. Upon initialization it creates a pipe and can be
notified once (hence the “single action” in the name). A
callable helper class is used to wait for notifications.

Signed-off-by: Guido Trotter <ultrotter@google.com>
Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>

This patch greatly simplifies the SharedLock code and implements
timeouts for the acquire() and delete() functions. A wrapper around
Python's threading.Condition class must be used to ensure thread
safety when check whether there are any waiters left.

Signed-off-by: Guido Trotter <ultrotter@google.com>
Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>