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Diffstat (limited to 'cloudinit/reporting/events.py')
| -rw-r--r-- | cloudinit/reporting/events.py | 210 |
1 files changed, 210 insertions, 0 deletions
diff --git a/cloudinit/reporting/events.py b/cloudinit/reporting/events.py new file mode 100644 index 00000000..e35e41dd --- /dev/null +++ b/cloudinit/reporting/events.py @@ -0,0 +1,210 @@ +# Copyright 2015 Canonical Ltd. +# This file is part of cloud-init. See LICENCE file for license information. +# +""" +cloud-init events + +Report events in a structured manner. +The events here are most likely used via reporting. +""" + +from . import instantiated_handler_registry + +FINISH_EVENT_TYPE = 'finish' +START_EVENT_TYPE = 'start' + + +class _nameset(set): + def __getattr__(self, name): + if name in self: + return name + raise AttributeError("%s not a valid value" % name) + + +status = _nameset(("SUCCESS", "WARN", "FAIL")) + + +class ReportingEvent(object): + """Encapsulation of event formatting.""" + + def __init__(self, event_type, name, description): + self.event_type = event_type + self.name = name + self.description = description + + def as_string(self): + """The event represented as a string.""" + return '{0}: {1}: {2}'.format( + self.event_type, self.name, self.description) + + def as_dict(self): + """The event represented as a dictionary.""" + return {'name': self.name, 'description': self.description, + 'event_type': self.event_type} + + +class FinishReportingEvent(ReportingEvent): + + def __init__(self, name, description, result=status.SUCCESS): + super(FinishReportingEvent, self).__init__( + FINISH_EVENT_TYPE, name, description) + self.result = result + if result not in status: + raise ValueError("Invalid result: %s" % result) + + def as_string(self): + return '{0}: {1}: {2}: {3}'.format( + self.event_type, self.name, self.result, self.description) + + def as_dict(self): + """The event represented as json friendly.""" + data = super(FinishReportingEvent, self).as_dict() + data['result'] = self.result + return data + + +def report_event(event): + """Report an event to all registered event handlers. + + This should generally be called via one of the other functions in + the reporting module. + + :param event_type: + The type of the event; this should be a constant from the + reporting module. + """ + for _, handler in instantiated_handler_registry.registered_items.items(): + handler.publish_event(event) + + +def report_finish_event(event_name, event_description, + result=status.SUCCESS): + """Report a "finish" event. + + See :py:func:`.report_event` for parameter details. + """ + event = FinishReportingEvent(event_name, event_description, result) + return report_event(event) + + +def report_start_event(event_name, event_description): + """Report a "start" event. + + :param event_name: + The name of the event; this should be a topic which events would + share (e.g. it will be the same for start and finish events). + + :param event_description: + A human-readable description of the event that has occurred. + """ + event = ReportingEvent(START_EVENT_TYPE, event_name, event_description) + return report_event(event) + + +class ReportEventStack(object): + """Context Manager for using :py:func:`report_event` + + This enables calling :py:func:`report_start_event` and + :py:func:`report_finish_event` through a context manager. + + :param name: + the name of the event + + :param description: + the event's description, passed on to :py:func:`report_start_event` + + :param message: + the description to use for the finish event. defaults to + :param:description. + + :param parent: + :type parent: :py:class:ReportEventStack or None + The parent of this event. The parent is populated with + results of all its children. The name used in reporting + is <parent.name>/<name> + + :param reporting_enabled: + Indicates if reporting events should be generated. + If not provided, defaults to the parent's value, or True if no parent + is provided. + + :param result_on_exception: + The result value to set if an exception is caught. default + value is FAIL. + """ + def __init__(self, name, description, message=None, parent=None, + reporting_enabled=None, result_on_exception=status.FAIL): + self.parent = parent + self.name = name + self.description = description + self.message = message + self.result_on_exception = result_on_exception + self.result = status.SUCCESS + + # use parents reporting value if not provided + if reporting_enabled is None: + if parent: + reporting_enabled = parent.reporting_enabled + else: + reporting_enabled = True + self.reporting_enabled = reporting_enabled + + if parent: + self.fullname = '/'.join((parent.fullname, name,)) + else: + self.fullname = self.name + self.children = {} + + def __repr__(self): + return ("ReportEventStack(%s, %s, reporting_enabled=%s)" % + (self.name, self.description, self.reporting_enabled)) + + def __enter__(self): + self.result = status.SUCCESS + if self.reporting_enabled: + report_start_event(self.fullname, self.description) + if self.parent: + self.parent.children[self.name] = (None, None) + return self + + def _childrens_finish_info(self): + for cand_result in (status.FAIL, status.WARN): + for name, (value, msg) in self.children.items(): + if value == cand_result: + return (value, self.message) + return (self.result, self.message) + + @property + def result(self): + return self._result + + @result.setter + def result(self, value): + if value not in status: + raise ValueError("'%s' not a valid result" % value) + self._result = value + + @property + def message(self): + if self._message is not None: + return self._message + return self.description + + @message.setter + def message(self, value): + self._message = value + + def _finish_info(self, exc): + # return tuple of description, and value + if exc: + return (self.result_on_exception, self.message) + return self._childrens_finish_info() + + def __exit__(self, exc_type, exc_value, traceback): + (result, msg) = self._finish_info(exc_value) + if self.parent: + self.parent.children[self.name] = (result, msg) + if self.reporting_enabled: + report_finish_event(self.fullname, msg, result) + +# vi: ts=4 expandtab |