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""" Gerrit event stream interface.
Class to listen to the Gerrit event stream and dispatch events.
"""
import json
import logging
from pygerrit.error import GerritError
from pygerrit.events import GerritEventFactory
class GerritStreamError(Exception):
""" Raised when an error occurs while reading the Gerrit events stream. """
pass
class GerritStream(object):
""" Gerrit events stream handler. """
def __init__(self):
self.listeners = []
def attach(self, listener):
""" Attach the `listener` to the list of listeners.
Raise GerritStreamError if the listener does not match the
expected signature, or if its event handler is not callable.
"""
if not hasattr(listener, "on_gerrit_event"):
raise GerritStreamError("Listener must have `on_gerrit_event` "
"event handler method")
if not callable(listener.on_gerrit_event):
raise GerritStreamError("`on_gerrit_event` must be callable")
if not listener.on_gerrit_event.func_code.co_argcount == 2:
raise GerritStreamError("`on_gerrit_event` must take 1 arg")
if not listener in self.listeners:
self.listeners.append(listener)
def detach(self, listener):
""" Remove the `listener` from the list of listeners. """
if listener in self.listeners:
try:
self.listeners.remove(listener)
except ValueError:
pass
def stream(self, inputstream):
""" Read lines of JSON data from `inputstream` and dispatch events.
For each line read from `inputstream`, until EOF, parse the line as
JSON data, instantiate the corresponding GerritEvent, and dispatch it
to the listeners.
Raise GerritStreamError on any errors.
"""
try:
while 1:
line = inputstream.readline()
if not line:
break
json_data = json.loads(line)
try:
event = GerritEventFactory.create(json_data)
for listener in self.listeners:
listener.on_gerrit_event(event)
except GerritError, e:
logging.error("Unable to dispatch event: %s", e)
except IOError, e:
raise GerritStreamError("Error reading event stream: %s" % e)
except ValueError, e:
raise GerritStreamError("Invalid JSON data in event stream: %s" % e)
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