[autotest] Add HostLockManager class, for locking/unlockin DUTs
An instance of HostLockManager is intended to be bound to a set of
hostnames shortly after instantiation. Thereafter, it can be used to
lock/unlock those hosts freely, until it is destroyed. At that time,
it will unlock() the associated hosts for you and complain that you
should've done it yourself.
This class is intended for use with dynamic_suite.Reimager and
dynamic_suite.Suite. The purpose is to allow Reimager.attempt() to
lock some hosts while allowing Suite.run_and_wait() to unlock them
during the course of its run. Therefore, a HostLockManager must be
instantiated _before_ we know what hosts are being reimaged, and live
after Reimager.attempt() has finished execution. Hence, the prime()
method that takes an iterable of hostnames.
BUG=chromium-os:30978
TEST=unit
Change-Id: I806a39ccc4951b011b2f7664aa4e942506829bbb
Reviewed-on: https://gerrit.chromium.org/gerrit/27204
Tested-by: Chris Masone <cmasone@chromium.org>
Reviewed-by: Scott Zawalski <scottz@chromium.org>
Commit-Ready: Chris Masone <cmasone@chromium.org>
diff --git a/server/cros/host_lock_manager.py b/server/cros/host_lock_manager.py
new file mode 100644
index 0000000..9fae09c
--- /dev/null
+++ b/server/cros/host_lock_manager.py
@@ -0,0 +1,90 @@
+# Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import logging
+
+import common
+from autotest_lib.client.common_lib import error
+from autotest_lib.server.cros import frontend_wrappers
+
+"""HostLockManager class, for the dynamic_suite module.
+
+A HostLockManager instance manages locking and unlocking a set of
+autotest DUTs. Once primed with a given set, it is bound to that set
+for the remainder of its lifetime and cannot be repurposed. If the
+caller fails to unlock() locked hosts before the instance is destroyed,
+it will attempt to unlock() the hosts automatically, but this is to be
+avoided.
+
+Usage:
+ manager = host_lock_manager.HostLockManager()
+ try:
+ manager.prime(['host1'])
+ manager.lock()
+ # do things
+ finally:
+ manager.unlock()
+"""
+
+class HostLockManager(object):
+ """
+ @var _afe: an instance of AFE as defined in server/frontend.py.
+ @var _hosts: an iterable of DUT hostnames.
+ @var _hosts_are_locked: whether we believe the hosts are locked
+ """
+
+
+ def __init__(self, afe=None):
+ """
+ Constructor
+
+ @param afe: an instance of AFE as defined in server/frontend.py.
+ """
+ self._afe = afe or frontend_wrappers.RetryingAFE(timeout_min=30,
+ delay_sec=10,
+ debug=False)
+ self._hosts = None
+ self._hosts_are_locked = False
+
+
+ def __del__(self):
+ if self._hosts_are_locked:
+ logging.error('Caller failed to unlock %r! '
+ 'Forcing unlock now.' % self._hosts)
+ self.unlock()
+
+
+ def prime(self, hosts):
+ """Permanently associate this instance with |hosts|.
+
+ @param hosts: iterable of hostnames to take over locking/unlocking.
+ @raise error.HostLockManagerReuse if already prime()d.
+ """
+ if not self._hosts:
+ self._hosts = frozenset(hosts)
+ else:
+ raise error.HostLockManagerReuse(
+ 'Already primed with %r.' % self._hosts)
+
+
+ def lock(self):
+ """Lock all DUTs in self._hosts."""
+ self._host_modifier(locked=True)
+ self._hosts_are_locked = True
+
+
+ def unlock(self):
+ """Unlock all DUTs in self._hosts."""
+ self._host_modifier(locked=False)
+ self._hosts_are_locked = False
+
+
+ def _host_modifier(self, **kwargs):
+ """Helper that runs the modify_host() RPC with specified args.
+
+ Passes kwargs through to the RPC directly.
+ """
+ self._afe.run('modify_hosts',
+ host_filter_data={'hostname__in': self._hosts},
+ update_data=kwargs)