10000 Fixing a performance issue in SSE client (#221) · firebase/firebase-admin-python@3e31716 · GitHub
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Fixing a performance issue in SSE client (#221)
* Fixing a performance issue in SSE client * Merged with master * Using a more efficient mechanism to buffer and parse incoming SSE data * Minor improvement to how tail string is read * Using string slicing to reduce the window * Updated comment
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‎CHANGELOG.md

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@@ -4,6 +4,8 @@
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type.googleapis.com/google.firebase.fcm.v1.FcmError to set error code.
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- [fixed] Ensuring that `UserRecord.tokens_valid_after_time` always
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returns an integer, and never returns `None`.
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- [fixed] Fixing a performance issue in the `db.listen()` API
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where it was taking a long time to process large RTDB nodes.
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# v2.13.0
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‎firebase_admin/_sseclient.py

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@@ -12,7 +12,10 @@
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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 stream realtime updates in the Firebase Database."""
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"""SSEClient module to stream realtime updates from the Firebase Database.
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Based on a similar implementation from Pyrebase.
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"""
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import re
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import time
@@ -37,6 +40,34 @@ def rebuild_auth(self, prepared_request, response):
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pass
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class _EventBuffer(object):
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"""A helper class for buffering and parsing raw SSE data."""
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def __init__(self):
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self._buffer = []
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self._tail = ''
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def append(self, char):
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self._buffer.append(char)
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self._tail += char
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self._tail = self._tail[-4:]
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def truncate(self):
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head, sep, _ = self.buffer_string.rpartition('\n')
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rem = head + sep
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self._buffer = list(rem)
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self._tail = rem[-4:]
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@property
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def is_end_of_field(self):
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last_two_chars = self._tail[-2:]
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return last_two_chars == '\n\n' or last_two_chars == '\r\r' or self._tail == '\r\n\r\n'
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@property
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def buffer_string(self):
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return ''.join(self._buffer)
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class SSEClient(object):
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"""SSE client implementation."""
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@@ -58,7 +89,7 @@ def __init__(self, url, session, retry=3000, **kwargs):
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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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# The SSE spec requires making requests with Cache-Control: no-cache
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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'
@@ -82,32 +113,28 @@ def _connect(self):
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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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return re.search(end_of_field, self.buf) is not None
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def __iter__(self):
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return self
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def __next__(self):
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while not self._event_complete():
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try:
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nextchar = next(self.resp_iterator)
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self.buf += nextchar
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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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self.buf = head + sep
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continue
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if not re.search(end_of_field, self.buf):
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temp_buffer = _EventBuffer()
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while not temp_buffer.is_end_of_field:
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try:
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nextchar = next(self.resp_iterator)
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temp_buffer.append(nextchar)
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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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temp_buffer.truncate()
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continue
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self.buf = temp_buffer.buffer_string
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split = re.split(end_of_field, self.buf)
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head = split[0]
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tail = ''.join(split[1:])
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self.buf = tail
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self.buf = '\n\n'.join(split[1:])
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event = Event.parse(head)
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if event.data == 'credential is no longer valid':
@@ -150,7 +177,7 @@ def parse(cls, raw):
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raw: the raw data to parse.
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Returns:
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Event: newly intialized ``Event`` object with the parameters initialized.
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Event: A new ``Event`` with the parameters initialized.
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"""
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event = cls()
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for line in raw.split('\n'):

‎tests/test_sseclient.py

Lines changed: 33 additions & 2 deletions
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@@ -19,10 +19,10 @@
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import six
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from firebase_admin import _sseclient
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from tests.testutils import MockAdapter
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from tests import testutils
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class MockSSEClientAdapter(MockAdapter):
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class MockSSEClientAdapter(testutils.MockAdapter):
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def __init__(self, payload, recorder):
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super(MockSSEClientAdapter, self).__init__(payload, 200, recorder)
@@ -73,6 +73,17 @@ def test_single_event(self):
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assert event_payload["path"] == "/"
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assert len(recorder) == 2
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def test_large_event(self):
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data = 'a' * int(0.1 * 1024 * 1024)
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payload = 'event: put\ndata: {"path":"/","data":"' + data + '"}\n\n'
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recorder = []
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sseclient = self.init_sse(payload, recorder)
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event = next(sseclient)
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event_payload = json.loads(event.data)
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assert event_payload["data"] == data
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assert event_payload["path"] == "/"
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assert len(recorder) == 1
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def test_multiple_events(self):
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payload = 'event: put\ndata: {"path":"/foo","data":"testevent1"}\n\n'
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payload += 'event: put\ndata: {"path":"/bar","data":"testevent2"}\n\n'
@@ -88,6 +99,26 @@ def test_multiple_events(self):
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assert event_payload["path"] == "/bar"
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assert len(recorder) == 1
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102+
def test_event_separators(self):
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payload = 'event: put\ndata: {"path":"/foo","data":"testevent1"}\n\n'
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payload += 'event: put\ndata: {"path":"/bar","data":"testevent2"}\r\r'
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payload += 'event: put\ndata: {"path":"/baz","data":"testevent3"}\r\n\r\n'
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recorder = []
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sseclient = self.init_sse(payload, recorder)
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event = next(sseclient)
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event_payload = json.loads(event.data)
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assert event_payload["data"] == "testevent1"
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assert event_payload["path"] == "/foo"
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event = next(sseclient)
113+
event_payload = json.loads(event.data)
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assert event_payload["data"] == "testevent2"
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assert event_payload["path"] == "/bar"
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event = next(sseclient)
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event_payload = json.loads(event.data)
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assert event_payload["data"] == "testevent3"
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assert event_payload["path"] == "/baz"
120+
assert len(recorder) == 1
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class TestEvent(object):
93124
"""Test cases for server-side events"""

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