Firebase db listener cannot handle with internet disconnetions

まず、issue に示されている SSEClient クラスと Event クラスを調べ、次に db.reference().listen() の実行中または実行後にネットワークを切断して失敗を再現します。listener がストリームの中断と再接続をどのように処理するかを追跡します。完了条件は、listener が Firebase の更新の受信を再開し、listen() の後のコードが無期限にブロックされないことです。

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  file a Github issue.
  • If this is a feature request make sure the issue title starts with "FR:".
• For general technical questions, post a question on StackOverflow
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  google group.
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[REQUIRED] Step 2: Describe your environment

• Operating System version: Ubuntu 18 and Raspbian
• Firebase SDK version: lasted realesed with pip install
• Library version: lasted realesed with pip install
• Firebase Product: firebase db stream (listener)

[REQUIRED] Step 3: Describe the problem

db.reference().listen() hang all code, do not run the rest of code, if when during connection of listener get internet disconnected, or if streamming allready connected and get disconnected for more than 2~3min and reconnect, do not get any updates from firebase.
i was searching for the root of this problem, and realised SSEclient have timeout default set by 3000, and the Event class retry time is set by None. Im not sure about this but maybe this is the problem?

Steps to reproduce:

To simulate the error we can just pull the cable or simply disconnect the internet from the system, wait 2 minutes to 3 minutes to reconnect it, after the reconnection, update any end-point that the streamming is listening. We can notice that we will not receive any updates.

It is also possible to simulate it during the streaming connection opening disconnect the internet and wait 2 to 3 minutes again and reconnect. We will not receive any updates from the firebase, and it will also be noticed that when this occurs, the codes below the opening stream do not run even wait for long time.

Relevant Code:

class SSEClient(object):
'''SSE client implementation.'''

def __init__(self, url, session, retry=3000, **kwargs):
    """Initializes the SSEClient.
    Args:
      url: The remote url to connect to.
      session: The requests session.
      retry: The retry interval in milliseconds (optional).
      **kwargs: Extra kwargs that will be sent to ``requests.get()`` (optional).
    """

class Event(object):
'''Event represents the events fired by SSE.'''

sse_line_pattern = re.compile('(?P<name>[^:]*):?( ?(?P<value>.*))?')

def __init__(self, data='', event_type='message', event_id=None, retry=None):
    self.data = data
    self.event_type = event_type
    self.event_id = event_id
    self.retry = retry

// TODO(you): code here to reproduce the problem

import firebase_admin
from firebase_admin import db
from firebase_admin import credentials

# Init Firebase.
dir_path = os.path.dirname(os.path.realpath(__file__))
cred = credentials.Certificate(dir_path + '/serviceAccountKey.json')
firebase_admin.initialize_app(cred, {
    'databaseURL': DB_URL
})

try:
    streaming = db.reference('path').listen(callback)
except ApiCallError:
    timer = 0

# did this code above to handle with disconnections.
timer = 100
while True:
    if internet_on():
        if timer == 0:
            try:
                streaming.close()
           except:
                #we do not have streaming connections open.
                pass
            try:
                streaming = db.reference('path').listen(callback)
                timer = 100
            except ApiCallError:
                timer = 0
    else:
        time.sleep(1)
        timer -= 1 if timer > 0 else 0