8000 Fixed and refactored the db.Reference.listen() API (#190) · devchetan/firebase-admin-python@62fb76d · GitHub
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hiranya911hiranya911
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Fixed and refactored the db.Reference.listen() API (firebase#190)
* Fixing a credentials issue in listener * Added more tests * Updated changelog * Further clean up and improvement * Improved error handling in listen() method
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‎CHANGELOG.md

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# Unreleased
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- [added] The `db.Reference` type now provides a `listen()` API for
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receiving realtime update events from the Firebase Database.
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- [added] The `db.reference()` method now optionally takes a `url`
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parameter. This can be used to access multiple Firebase Databases
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in the same project more easily.

‎firebase_admin/_sseclient.py

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# Copyright 2017 Google Inc.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""SSEClient module to handle streaming of realtime changes on the database
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to the firebase-admin-sdk
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"""
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"""SSEClient module to stream realtime updates in the Firebase Database."""
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import re
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import time
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import warnings
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import six
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from google.auth import transport
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import requests
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@@ -26,80 +27,63 @@
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end_of_field = re.compile(r'\r\n\r\n|\r\r|\n\n')
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class KeepAuthSession(requests.Session):
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"""A session that does not drop Authentication on redirects between domains"""
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class KeepAuthSession(transport.requests.AuthorizedSession):
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"""A session that does not drop authentication on redirects between domains."""
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def __init__(self, credential):
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super(KeepAuthSession, self).__init__(credential)
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def rebuild_auth(self, prepared_request, response):
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pass
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class SSEClient(object):
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"""SSE Client Class"""
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"""SSE client implementation."""
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def __init__(self, url, session, retry=3000, **kwargs):
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"""Initializes the SSEClient.
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def __init__(self, url, session, last_id=None, retry=3000, **kwargs):
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"""Initialize the SSEClient
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Args:
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url: the url to connect to
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session: the requests.session()
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last_id: optional id
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retry: the interval in ms
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**kwargs: extra kwargs will be sent to requests.get
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url: The remote url to connect to.
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session: The requests session.
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retry: The retry interval in milliseconds (optional).
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**kwargs: Extra kwargs that will be sent to ``requests.get()`` (optional).
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"""
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self.should_connect = True
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self.url = url
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self.last_id = last_id
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self.retry = retry
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self.session = session
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self.retry = retry
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self.requests_kwargs = kwargs
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self.should_connect = True
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self.last_id = None
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self.buf = u'' # Keep data here as it streams in
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headers = self.requests_kwargs.get('headers', {})
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# The SSE spec requires making requests with Cache-Control: nocache
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headers['Cache-Control'] = 'no-cache'
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# The 'Accept' header is not required, but explicit > implicit
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headers['Accept'] = 'text/event-stream'
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self.requests_kwargs['headers'] = headers
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# Keep data here as it streams in
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self.buf = u''
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self._connect()
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def close(self):
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"""Close the SSE Client instance"""
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# TODO: check if AttributeError is needed to catch here
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"""Closes the SSEClient instance."""
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self.should_connect = False
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self.retry = 0
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self.resp.close()
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# self.resp.raw._fp.fp.raw._sock.shutdown(socket.SHUT_RDWR)
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# self.resp.raw._fp.fp.raw._sock.close()
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7774
def _connect(self):
78-
"""connects to the server using requests"""
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"""Connects to the server using requests."""
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if self.should_connect:
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success = False
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while not success:
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if self.last_id:
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self.requests_kwargs['headers']['Last-Event-ID'] = self.last_id
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# Use session if set. Otherwise fall back to requests module.
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self.requester = self.session or requests
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self.resp = self.requester.get(self.url, stream=True, **self.requests_kwargs)
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self.resp_iterator = self.resp.iter_content(decode_unicode=True)
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# TODO: Ensure we're handling redirects. Might also stick the 'origin'
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# attribute on Events like the Javascript spec requires.
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self.resp.raise_for_status()
93-
success = True
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if self.last_id:
78+
self.requests_kwargs['headers']['Last-Event-ID'] = self.last_id
79+
self.resp = self.session.get(self.url, stream=True, **self.requests_kwargs)
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self.resp_iterator = self.resp.iter_content(decode_unicode=True)
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self.resp.raise_for_status()
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else:
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raise StopIteration()
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def _event_complete(self):
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"""Checks if the event is completed by matching regular expression
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Returns:
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boolean: True if the regex matched meaning end of event, else False
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"""
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"""Checks if the event is completed by matching regular expression."""
10387
return re.search(end_of_field, self.buf) is not None
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10589
def __iter__(self):
@@ -113,8 +97,6 @@ def __next__(self):
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F438 except (StopIteration, requests.RequestException):
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time.sleep(self.retry / 1000.0)
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self._connect()
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# The SSE spec only supports resuming from a whole message, so
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# if we have half a message we should throw it out.
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head, sep, tail = self.buf.rpartition('\n')
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124106
split = re.split(end_of_field, self.buf)
125107
head = split[0]
126-
tail = "".join(split[1:])
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tail = ''.join(split[1:])
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128110
self.buf = tail
129-
msg = Event.parse(head)
111+
event = Event.parse(head)
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131-
if msg.data == "credential is no longer valid":
113+
if event.data == 'credential is no longer valid':
132114
self._connect()
133115
return None
134-
135-
if msg.data == 'null':
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elif event.data == 'null':
136117
return None
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138119
# If the server requests a specific retry delay, we need to honor it.
139-
if msg.retry:
140-
self.retry = msg.retry
120+
if event.retry:
121+
self.retry = event.retry
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142123
# last_id should only be set if included in the message. It's not
143124
# forgotten if a message omits it.
144-
if msg.event_id:
145-
self.last_id = msg.event_id
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return msg
125+
if event.event_id:
126+
self.last_id = event.event_id
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return event
148128

149-
if six.PY2:
150-
next = __next__
129+
def next(self):
130+
return self.__next__()
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class Event(object):
154-
"""Event class to handle the events fired by SSE"""
134+
"""Event represents the events fired by SSE."""
155135

156136
sse_line_pattern = re.compile('(?P<name>[^:]*):?( ?(?P<value>.*))?')
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158-
def __init__(self, data='', event='message', event_id=None, retry=None):
138+
def __init__(self, data='', event_type='message', event_id=None, retry=None):
159139
self.data = data
160-
self.event = event
140+
self.event_type = event_type
161141
self.event_id = event_id
162142
self.retry = retry
163143

164144
@classmethod
165145
def parse(cls, raw):
166-
"""Given a possibly-multiline string representing an SSE message, parse it
167-
and return a Event object.
146+
"""Given a possibly-multiline string representing an SSE message, parses it
147+
and returns an Event object.
168148
169149
Args:
170-
raw: the raw data to parse
150+
raw: the raw data to parse.
171151
172152
Returns:
173-
Event: newly intialized Event() object with the parameters initialized
153+
Event: newly intialized ``Event`` object with the parameters initialized.
174154
"""
175-
msg = cls()
155+
event = cls()
176156
for line in raw.split('\n'):
177157
match = cls.sse_line_pattern.match(line)
178158
if match is None:
@@ -185,22 +165,17 @@ def parse(cls, raw):
185165
if name == '':
186166
# line began with a ":", so is a comment. Ignore
187167
continue
188-
189-
if name == 'data':
168+
elif name == 'data':
190169
# If we already have some data, then join to it with a newline.
191170
# Else this is it.
192-
if msg.data:
193-
msg.data = '%s\n%s' % (msg.data, value)
171+
if event.data:
172+
event.data = '%s\n%s' % (event.data, value)
194173
else:
195-
msg.data = value
174+
event.data = value
196175
elif name == 'event':
197-
msg.event = value
176+
event.event_type = value
198177
elif name == 'id':
199-
msg.event_id = value
178+
event.event_id = value
200179
elif name == 'retry':
201-
msg.retry = int(value)
202-
203-
return msg
204-
205-
def __str__(self):
206-
return self.data
180+
event.retry = int(value)
181+
return event

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