def get_power_state(system_id, hostname, power_type, context, clock=reactor):
"""Return the power state of the given node.
:return: The string "on", "off" or "unknown".
:raises PowerActionFail: When there's a failure querying the node's
power state.
"""
def check_power_state(state):
if state not in ("on", "off", "unknown"):
# This is considered an error.
raise PowerActionFail(state)
# Capture errors as we go along.
exc_info = None, None, None
power_driver = PowerDriverRegistry.get_item(power_type)
if power_driver is None:
raise PowerActionFail("Unknown power_type '%s'" % power_type)
missing_packages = power_driver.detect_missing_packages()
if len(missing_packages):
raise PowerActionFail(
"'%s' package(s) are not installed" % ", ".join(missing_packages)
)
try:
power_state = yield perform_power_driver_query(
system_id, hostname, power_type, context
)
check_power_state(power_state)
except Exception:
# Hold the error; it will be reported later.
exc_info = sys.exc_info()
else:
returnValue(power_state)
# Reaching here means that things have gone wrong.
assert exc_info != (None, None, None)
exc_type, exc_value, exc_trace = exc_info
raise exc_type(exc_value).with_traceback(exc_trace)
def check_power_state(state):
if state not in ("on", "off", "unknown"):
# This is considered an error.
raise PowerActionFail(state)
def maybe_change_power_state(system_id,
hostname,
power_type,
power_change,
context,
clock=reactor):
"""Attempt to change the power state of a node.
If there is no power action already in progress, register this
action and then pass change_power_state() to the reactor to call
later and then return.
This function exists to guarantee that PowerActionAlreadyInProgress
errors will be raised promptly, before any work is done to power the
node on.
:raises: PowerActionAlreadyInProgress if there's already a power
action in progress for this node.
"""
assert power_change in ("on", "off",
"cycle"), ("Unknown power change: %s" %
power_change)
power_driver = PowerDriverRegistry.get_item(power_type)
if power_driver is None:
raise PowerActionFail("Unknown power_type '%s'" % power_type)
missing_packages = power_driver.detect_missing_packages()
if len(missing_packages):
raise PowerActionFail("'%s' package(s) are not installed" %
" ".join(missing_packages))
# There should be one and only one power change for each system ID.
if system_id in power_action_registry:
current_power_change, d = power_action_registry[system_id]
else:
current_power_change, d = None, None
if current_power_change is None:
# Arrange for the power change to happen later; do not make the caller
# wait, because it might take a long time. We set a timeout so that if
# the power action doesn't return in a timely fashion (or fails
# silently or some such) it doesn't block other actions on the node.
d = deferLater(
clock,
0,
deferWithTimeout,
CHANGE_POWER_STATE_TIMEOUT,
change_power_state,
system_id,
hostname,
power_type,
power_change,
context,
clock,
)
power_action_registry[system_id] = power_change, d
# Whether we succeed or fail, we need to remove the action from the
# registry of actions, otherwise subsequent actions will fail.
d.addBoth(callOut, power_action_registry.pop, system_id, None)
# Log cancellations distinctly from other errors.
def eb_cancelled(failure):
failure.trap(CancelledError)
log.msg("%s: Power could not be set to %s; timed out." %
(hostname, power_change))
return power_change_failure(system_id, hostname, power_change,
"Timed out")
d.addErrback(eb_cancelled)
# Catch-all log.
d.addErrback(log.err,
"%s: Power %s failed." % (hostname, power_change))
# LP: 1761600 - Returning d will cause d to be resolved with the
# caller. This causes power actions in the UI/API such as deploy,
# commission, or release to wait for the power action to complete
# before finishing.
elif current_power_change == power_change:
# What we want is already happening; let it continue.
pass
else:
# Right now we reject conflicting power changes. However, we have the
# Deferred (in `d`) along which the current power change is occurring,
# so the option to cancel is available if we want it.
raise PowerActionAlreadyInProgress(
"Unable to change power state to '%s' for node %s: another "
"action is already in progress for that node." %
(power_change, hostname))