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https://github.com/valitydev/salt.git
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Fix race condition when returning events from commands
It has been observed that when running this command: ``` salt "*" test.ping ``` sometimes the command would return `Minion did not return. [No response]` for some of the minions even though the minions did indeed respond (reproduced running Windows salt-master on Python 3 using the TCP transport). After investigating this further, it seems that there is a race condition where if the response via event happens before events are being listened for, the response is lost. For instance, in `salt.client.LocalClient.cmd_cli` which is what is invoked in the command above, it won't start listening for events until `get_cli_event_returns` which invokes `get_iter_returns` which invokes `get_returns_no_block` which invokes `self.event.get_event` which will connect to the event bus if it hasn't connected yet (which is the case the first time it hits this code). But events may be fired anytime after `self.pub()` is executed which occurs before this code. We need to ensure that events are being listened for before it is possible they return. We also want to avoid issue #31454 which is what PR #36024 fixed but in turn caused this issue. This is the approach I have taken to try to tackle this issue: It doesn't seem possible to generically discern if events can be returned by a given function that invokes `run_job` and contains an event searching function such as `get_cli_event_returns`. So for all such functions that could possibly need to search the event bus, we do the following: - Record if the event bus is currently being listened to. - When invoking `run_job`, ensure that `listen=True` so that `self.pub()` will ensure that the event bus is listed to before sending the payload. - When all possible event bus activities are concluded, if the event bus was not originally being listened to, stop listening to it. This is designed so that issue #31454 does not reappear. We do this via a try/finally block in all instances of such code. Signed-off-by: Sergey Kizunov <sergey.kizunov@ni.com>
This commit is contained in:
Sergey Kizunov
parent
fb2add012f
commit
c59a5adb0d
@ -290,6 +290,7 @@ class LocalClient(object):
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timeout=None,
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jid='',
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kwarg=None,
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listen=False,
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**kwargs):
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'''
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Asynchronously send a command to connected minions
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@ -316,6 +317,7 @@ class LocalClient(object):
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ret,
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jid=jid,
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timeout=self._get_timeout(timeout),
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listen=listen,
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**kwargs)
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except SaltClientError:
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# Re-raise error with specific message
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@ -564,32 +566,38 @@ class LocalClient(object):
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function name.
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'''
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arg = salt.utils.args.condition_input(arg, kwarg)
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pub_data = self.run_job(tgt,
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fun,
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arg,
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expr_form,
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ret,
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timeout,
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jid,
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**kwargs)
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was_listening = self.event.cpub
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if not pub_data:
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return pub_data
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try:
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pub_data = self.run_job(tgt,
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fun,
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arg,
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expr_form,
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ret,
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timeout,
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jid,
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listen=True,
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**kwargs)
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ret = {}
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for fn_ret in self.get_cli_event_returns(
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pub_data['jid'],
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pub_data['minions'],
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self._get_timeout(timeout),
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tgt,
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expr_form,
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**kwargs):
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if not pub_data:
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return pub_data
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if fn_ret:
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for mid, data in six.iteritems(fn_ret):
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ret[mid] = data.get('ret', {})
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ret = {}
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for fn_ret in self.get_cli_event_returns(
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pub_data['jid'],
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pub_data['minions'],
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self._get_timeout(timeout),
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tgt,
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expr_form,
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**kwargs):
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return ret
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if fn_ret:
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for mid, data in six.iteritems(fn_ret):
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ret[mid] = data.get('ret', {})
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return ret
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finally:
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if not was_listening:
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self.event.close_pub()
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def cmd_cli(
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self,
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@ -614,40 +622,47 @@ class LocalClient(object):
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:returns: A generator
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'''
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arg = salt.utils.args.condition_input(arg, kwarg)
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pub_data = self.run_job(
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tgt,
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fun,
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arg,
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expr_form,
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ret,
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timeout,
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**kwargs)
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was_listening = self.event.cpub
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if not pub_data:
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yield pub_data
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else:
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try:
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for fn_ret in self.get_cli_event_returns(
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pub_data['jid'],
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pub_data['minions'],
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self._get_timeout(timeout),
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tgt,
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expr_form,
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verbose,
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progress,
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**kwargs):
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try:
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pub_data = self.run_job(
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tgt,
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fun,
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arg,
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expr_form,
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ret,
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timeout,
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listen=True,
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**kwargs)
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if not fn_ret:
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continue
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if not pub_data:
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yield pub_data
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else:
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try:
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for fn_ret in self.get_cli_event_returns(
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pub_data['jid'],
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pub_data['minions'],
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self._get_timeout(timeout),
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tgt,
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expr_form,
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verbose,
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progress,
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**kwargs):
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yield fn_ret
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except KeyboardInterrupt:
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msg = ('Exiting on Ctrl-C\nThis job\'s jid is:\n{0}\n'
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'The minions may not have all finished running and any '
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'remaining minions will return upon completion. To '
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'look up the return data for this job later run:\n'
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'salt-run jobs.lookup_jid {0}').format(pub_data['jid'])
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raise SystemExit(msg)
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if not fn_ret:
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continue
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yield fn_ret
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except KeyboardInterrupt:
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msg = ('Exiting on Ctrl-C\nThis job\'s jid is:\n{0}\n'
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'The minions may not have all finished running and any '
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'remaining minions will return upon completion. To '
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'look up the return data for this job later run:\n'
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'salt-run jobs.lookup_jid {0}').format(pub_data['jid'])
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raise SystemExit(msg)
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finally:
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if not was_listening:
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self.event.close_pub()
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def cmd_iter(
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self,
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@ -677,30 +692,37 @@ class LocalClient(object):
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{'stewart': {'ret': True}}
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'''
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arg = salt.utils.args.condition_input(arg, kwarg)
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pub_data = self.run_job(
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tgt,
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fun,
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arg,
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expr_form,
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ret,
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timeout,
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**kwargs)
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was_listening = self.event.cpub
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if not pub_data:
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yield pub_data
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else:
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if kwargs.get('yield_pub_data'):
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try:
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pub_data = self.run_job(
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tgt,
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fun,
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arg,
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expr_form,
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ret,
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timeout,
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listen=True,
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**kwargs)
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if not pub_data:
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yield pub_data
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for fn_ret in self.get_iter_returns(pub_data['jid'],
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pub_data['minions'],
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timeout=self._get_timeout(timeout),
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tgt=tgt,
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tgt_type=expr_form,
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**kwargs):
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if not fn_ret:
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continue
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yield fn_ret
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self._clean_up_subscriptions(pub_data['jid'])
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else:
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if kwargs.get('yield_pub_data'):
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yield pub_data
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for fn_ret in self.get_iter_returns(pub_data['jid'],
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pub_data['minions'],
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timeout=self._get_timeout(timeout),
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tgt=tgt,
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tgt_type=expr_form,
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**kwargs):
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if not fn_ret:
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continue
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yield fn_ret
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self._clean_up_subscriptions(pub_data['jid'])
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finally:
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if not was_listening:
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self.event.close_pub()
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def cmd_iter_no_block(
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self,
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@ -737,31 +759,38 @@ class LocalClient(object):
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{'stewart': {'ret': True}}
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'''
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arg = salt.utils.args.condition_input(arg, kwarg)
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pub_data = self.run_job(
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tgt,
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fun,
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arg,
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expr_form,
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ret,
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timeout,
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**kwargs)
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was_listening = self.event.cpub
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if not pub_data:
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yield pub_data
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else:
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for fn_ret in self.get_iter_returns(pub_data['jid'],
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pub_data['minions'],
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timeout=timeout,
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tgt=tgt,
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tgt_type=expr_form,
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block=False,
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**kwargs):
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if fn_ret and any([show_jid, verbose]):
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for minion in fn_ret.keys():
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fn_ret[minion]['jid'] = pub_data['jid']
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yield fn_ret
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try:
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pub_data = self.run_job(
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tgt,
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fun,
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arg,
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expr_form,
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ret,
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timeout,
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listen=True,
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**kwargs)
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self._clean_up_subscriptions(pub_data['jid'])
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if not pub_data:
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yield pub_data
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else:
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for fn_ret in self.get_iter_returns(pub_data['jid'],
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pub_data['minions'],
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timeout=timeout,
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tgt=tgt,
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tgt_type=expr_form,
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block=False,
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**kwargs):
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if fn_ret and any([show_jid, verbose]):
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for minion in fn_ret.keys():
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fn_ret[minion]['jid'] = pub_data['jid']
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yield fn_ret
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self._clean_up_subscriptions(pub_data['jid'])
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finally:
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if not was_listening:
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self.event.close_pub()
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def cmd_full_return(
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self,
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@ -778,24 +807,31 @@ class LocalClient(object):
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Execute a salt command and return
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'''
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arg = salt.utils.args.condition_input(arg, kwarg)
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pub_data = self.run_job(
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tgt,
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fun,
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arg,
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expr_form,
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ret,
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timeout,
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**kwargs)
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was_listening = self.event.cpub
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if not pub_data:
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return pub_data
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try:
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pub_data = self.run_job(
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tgt,
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fun,
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arg,
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expr_form,
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ret,
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timeout,
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listen=True,
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**kwargs)
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return (self.get_cli_static_event_returns(pub_data['jid'],
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pub_data['minions'],
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timeout,
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tgt,
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expr_form,
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verbose))
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if not pub_data:
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return pub_data
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return (self.get_cli_static_event_returns(pub_data['jid'],
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pub_data['minions'],
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timeout,
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tgt,
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expr_form,
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verbose))
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finally:
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if not was_listening:
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self.event.close_pub()
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def get_cli_returns(
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self,
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@ -1460,6 +1496,7 @@ class LocalClient(object):
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ret='',
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jid='',
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timeout=5,
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listen=False,
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**kwargs):
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'''
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Take the required arguments and publish the given command.
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@ -1509,6 +1546,10 @@ class LocalClient(object):
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master_uri=master_uri)
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try:
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# Ensure that the event subscriber is connected.
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# If not, we won't get a response, so error out
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if listen and not self.event.connect_pub(timeout=timeout):
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raise SaltReqTimeoutError()
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payload = channel.send(payload_kwargs, timeout=timeout)
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except SaltReqTimeoutError:
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raise SaltReqTimeoutError(
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@ -365,6 +365,18 @@ class SaltEvent(object):
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self.cpub = True
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return self.cpub
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def close_pub(self):
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'''
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Close the publish connection (if established)
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'''
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if not self.cpub:
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return
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self.subscriber.close()
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self.subscriber = None
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self.pending_events = []
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self.cpub = False
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def connect_pull(self, timeout=1):
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'''
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Establish a connection with the event pull socket
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