prompt: We are currently solving the following issue within our repository. Here is the issue text:
  --- BEGIN ISSUE ---
  Unnecessary ping event
  **Environment**:
  
  - CTFd Version/Commit: 3.1.1, latest commit
  - Operating System: any
  - Web Browser and Version: any
  
  in the comment you said "Immediately yield a ping event to force Response headers to be set", but this event seems to lies inside the while True loop, which results to an unnecessary ping event every 5 seconds.
  I believe that's an unintended behavior, though it doesn't break anything.
  
  https://github.com/CTFd/CTFd/blob/4c31dc23e8cfa0308367732d603b16e01871b00e/CTFd/utils/events/__init__.py#L57-L67
  
  --- END ISSUE ---
  
  Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
  --- BEGIN FILES ---
  Path: `CTFd/utils/events/__init__.py`
  Content:
  ```
  1 import json
  2 from collections import defaultdict
  3 from queue import Queue
  4 
  5 from gevent import Timeout, spawn
  6 from tenacity import retry, wait_exponential
  7 
  8 from CTFd.cache import cache
  9 from CTFd.utils import string_types
  10 
  11 
  12 class ServerSentEvent(object):
  13     def __init__(self, data, type=None, id=None):
  14         self.data = data
  15         self.type = type
  16         self.id = id
  17 
  18     def __str__(self):
  19         if isinstance(self.data, string_types):
  20             data = self.data
  21         else:
  22             data = json.dumps(self.data)
  23         lines = ["data:{value}".format(value=line) for line in data.splitlines()]
  24         if self.type:
  25             lines.insert(0, "event:{value}".format(value=self.type))
  26         if self.id:
  27             lines.append("id:{value}".format(value=self.id))
  28         return "\n".join(lines) + "\n\n"
  29 
  30     def to_dict(self):
  31         d = {"data": self.data}
  32         if self.type:
  33             d["type"] = self.type
  34         if self.id:
  35             d["id"] = self.id
  36         return d
  37 
  38 
  39 class EventManager(object):
  40     def __init__(self):
  41         self.clients = {}
  42 
  43     def publish(self, data, type=None, channel="ctf"):
  44         event = ServerSentEvent(data, type=type)
  45         message = event.to_dict()
  46         for client in list(self.clients.values()):
  47             client[channel].put(message)
  48         return len(self.clients)
  49 
  50     def listen(self):
  51         pass
  52 
  53     def subscribe(self, channel="ctf"):
  54         q = defaultdict(Queue)
  55         self.clients[id(q)] = q
  56         try:
  57             while True:
  58                 try:
  59                     # Immediately yield a ping event to force Response headers to be set
  60                     # or else some reverse proxies will incorrectly buffer SSE
  61                     yield ServerSentEvent(data="", type="ping")
  62 
  63                     with Timeout(5):
  64                         message = q[channel].get()
  65                         yield ServerSentEvent(**message)
  66                 except Timeout:
  67                     yield ServerSentEvent(data="", type="ping")
  68         finally:
  69             del self.clients[id(q)]
  70             del q
  71 
  72 
  73 class RedisEventManager(EventManager):
  74     def __init__(self):
  75         super(EventManager, self).__init__()
  76         self.client = cache.cache._write_client
  77         self.clients = {}
  78 
  79     def publish(self, data, type=None, channel="ctf"):
  80         event = ServerSentEvent(data, type=type)
  81         message = json.dumps(event.to_dict())
  82         return self.client.publish(message=message, channel=channel)
  83 
  84     def listen(self, channel="ctf"):
  85         @retry(wait=wait_exponential(min=1, max=30))
  86         def _listen():
  87             while True:
  88                 pubsub = self.client.pubsub()
  89                 pubsub.subscribe(channel)
  90                 try:
  91                     while True:
  92                         message = pubsub.get_message(
  93                             ignore_subscribe_messages=True, timeout=5
  94                         )
  95                         if message:
  96                             if message["type"] == "message":
  97                                 event = json.loads(message["data"])
  98                                 for client in list(self.clients.values()):
  99                                     client[channel].put(event)
  100                 finally:
  101                     pubsub.close()
  102 
  103         spawn(_listen)
  104 
  105     def subscribe(self, channel="ctf"):
  106         q = defaultdict(Queue)
  107         self.clients[id(q)] = q
  108         try:
  109             while True:
  110                 try:
  111                     # Immediately yield a ping event to force Response headers to be set
  112                     # or else some reverse proxies will incorrectly buffer SSE
  113                     yield ServerSentEvent(data="", type="ping")
  114 
  115                     with Timeout(5):
  116                         message = q[channel].get()
  117                         yield ServerSentEvent(**message)
  118                 except Timeout:
  119                     yield ServerSentEvent(data="", type="ping")
  120         finally:
  121             del self.clients[id(q)]
  122             del q
  123
  ```
  --- END FILES ---
  
  Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.
  
  Here is an example:
  
  ```diff
  diff --git a/examples/server_async.py b/examples/server_async.py
  --- a/examples/server_async.py
  +++ b/examples/server_async.py
  @@ -313,4 +313,4 @@
   
   
   if __name__ == "__main__":
  -    asyncio.run(run_async_server("."), debug=True)
  +    asyncio.run(run_async_server(), debug=True)
  diff --git a/examples/server_sync.py b/examples/server_sync.py
  --- a/examples/server_sync.py
  +++ b/examples/server_sync.py
  @@ -313,5 +313,5 @@
   
   
   if __name__ == "__main__":
  -    server = run_sync_server(".")
  +    server = run_sync_server()
       server.shutdown()
  
  ```
  
golden_diff: diff --git a/CTFd/utils/events/__init__.py b/CTFd/utils/events/__init__.py
  --- a/CTFd/utils/events/__init__.py
  +++ b/CTFd/utils/events/__init__.py
  @@ -54,12 +54,11 @@
           q = defaultdict(Queue)
           self.clients[id(q)] = q
           try:
  +            # Immediately yield a ping event to force Response headers to be set
  +            # or else some reverse proxies will incorrectly buffer SSE
  +            yield ServerSentEvent(data="", type="ping")
               while True:
                   try:
  -                    # Immediately yield a ping event to force Response headers to be set
  -                    # or else some reverse proxies will incorrectly buffer SSE
  -                    yield ServerSentEvent(data="", type="ping")
  -
                       with Timeout(5):
                           message = q[channel].get()
                           yield ServerSentEvent(**message)
  @@ -106,12 +105,11 @@
           q = defaultdict(Queue)
           self.clients[id(q)] = q
           try:
  +            # Immediately yield a ping event to force Response headers to be set
  +            # or else some reverse proxies will incorrectly buffer SSE
  +            yield ServerSentEvent(data="", type="ping")
               while True:
                   try:
  -                    # Immediately yield a ping event to force Response headers to be set
  -                    # or else some reverse proxies will incorrectly buffer SSE
  -                    yield ServerSentEvent(data="", type="ping")
  -
                       with Timeout(5):
                           message = q[channel].get()
                           yield ServerSentEvent(**message)
  
verification_info: {"golden_diff": "diff --git a/CTFd/utils/events/__init__.py b/CTFd/utils/events/__init__.py\n--- a/CTFd/utils/events/__init__.py\n+++ b/CTFd/utils/events/__init__.py\n@@ -54,12 +54,11 @@\n         q = defaultdict(Queue)\n         self.clients[id(q)] = q\n         try:\n+            # Immediately yield a ping event to force Response headers to be set\n+            # or else some reverse proxies will incorrectly buffer SSE\n+            yield ServerSentEvent(data=\"\", type=\"ping\")\n             while True:\n                 try:\n-                    # Immediately yield a ping event to force Response headers to be set\n-                    # or else some reverse proxies will incorrectly buffer SSE\n-                    yield ServerSentEvent(data=\"\", type=\"ping\")\n-\n                     with Timeout(5):\n                         message = q[channel].get()\n                         yield ServerSentEvent(**message)\n@@ -106,12 +105,11 @@\n         q = defaultdict(Queue)\n         self.clients[id(q)] = q\n         try:\n+            # Immediately yield a ping event to force Response headers to be set\n+            # or else some reverse proxies will incorrectly buffer SSE\n+            yield ServerSentEvent(data=\"\", type=\"ping\")\n             while True:\n                 try:\n-                    # Immediately yield a ping event to force Response headers to be set\n-                    # or else some reverse proxies will incorrectly buffer SSE\n-                    yield ServerSentEvent(data=\"\", type=\"ping\")\n-\n                     with Timeout(5):\n                         message = q[channel].get()\n                         yield ServerSentEvent(**message)\n", "issue": "Unnecessary ping event\n**Environment**:\r\n\r\n- CTFd Version/Commit: 3.1.1, latest commit\r\n- Operating System: any\r\n- Web Browser and Version: any\r\n\r\nin the comment you said \"Immediately yield a ping event to force Response headers to be set\", but this event seems to lies inside the while True loop, which results to an unnecessary ping event every 5 seconds.\r\nI believe that's an unintended behavior, though it doesn't break anything.\r\n\r\nhttps://github.com/CTFd/CTFd/blob/4c31dc23e8cfa0308367732d603b16e01871b00e/CTFd/utils/events/__init__.py#L57-L67\n", "before_files": [{"content": "import json\nfrom collections import defaultdict\nfrom queue import Queue\n\nfrom gevent import Timeout, spawn\nfrom tenacity import retry, wait_exponential\n\nfrom CTFd.cache import cache\nfrom CTFd.utils import string_types\n\n\nclass ServerSentEvent(object):\n    def __init__(self, data, type=None, id=None):\n        self.data = data\n        self.type = type\n        self.id = id\n\n    def __str__(self):\n        if isinstance(self.data, string_types):\n            data = self.data\n        else:\n            data = json.dumps(self.data)\n        lines = [\"data:{value}\".format(value=line) for line in data.splitlines()]\n        if self.type:\n            lines.insert(0, \"event:{value}\".format(value=self.type))\n        if self.id:\n            lines.append(\"id:{value}\".format(value=self.id))\n        return \"\\n\".join(lines) + \"\\n\\n\"\n\n    def to_dict(self):\n        d = {\"data\": self.data}\n        if self.type:\n            d[\"type\"] = self.type\n        if self.id:\n            d[\"id\"] = self.id\n        return d\n\n\nclass EventManager(object):\n    def __init__(self):\n        self.clients = {}\n\n    def publish(self, data, type=None, channel=\"ctf\"):\n        event = ServerSentEvent(data, type=type)\n        message = event.to_dict()\n        for client in list(self.clients.values()):\n            client[channel].put(message)\n        return len(self.clients)\n\n    def listen(self):\n        pass\n\n    def subscribe(self, channel=\"ctf\"):\n        q = defaultdict(Queue)\n        self.clients[id(q)] = q\n        try:\n            while True:\n                try:\n                    # Immediately yield a ping event to force Response headers to be set\n                    # or else some reverse proxies will incorrectly buffer SSE\n                    yield ServerSentEvent(data=\"\", type=\"ping\")\n\n                    with Timeout(5):\n                        message = q[channel].get()\n                        yield ServerSentEvent(**message)\n                except Timeout:\n                    yield ServerSentEvent(data=\"\", type=\"ping\")\n        finally:\n            del self.clients[id(q)]\n            del q\n\n\nclass RedisEventManager(EventManager):\n    def __init__(self):\n        super(EventManager, self).__init__()\n        self.client = cache.cache._write_client\n        self.clients = {}\n\n    def publish(self, data, type=None, channel=\"ctf\"):\n        event = ServerSentEvent(data, type=type)\n        message = json.dumps(event.to_dict())\n        return self.client.publish(message=message, channel=channel)\n\n    def listen(self, channel=\"ctf\"):\n        @retry(wait=wait_exponential(min=1, max=30))\n        def _listen():\n            while True:\n                pubsub = self.client.pubsub()\n                pubsub.subscribe(channel)\n                try:\n                    while True:\n                        message = pubsub.get_message(\n                            ignore_subscribe_messages=True, timeout=5\n                        )\n                        if message:\n                            if message[\"type\"] == \"message\":\n                                event = json.loads(message[\"data\"])\n                                for client in list(self.clients.values()):\n                                    client[channel].put(event)\n                finally:\n                    pubsub.close()\n\n        spawn(_listen)\n\n    def subscribe(self, channel=\"ctf\"):\n        q = defaultdict(Queue)\n        self.clients[id(q)] = q\n        try:\n            while True:\n                try:\n                    # Immediately yield a ping event to force Response headers to be set\n                    # or else some reverse proxies will incorrectly buffer SSE\n                    yield ServerSentEvent(data=\"\", type=\"ping\")\n\n                    with Timeout(5):\n                        message = q[channel].get()\n                        yield ServerSentEvent(**message)\n                except Timeout:\n                    yield ServerSentEvent(data=\"\", type=\"ping\")\n        finally:\n            del self.clients[id(q)]\n            del q\n", "path": "CTFd/utils/events/__init__.py"}], "after_files": [{"content": "import json\nfrom collections import defaultdict\nfrom queue import Queue\n\nfrom gevent import Timeout, spawn\nfrom tenacity import retry, wait_exponential\n\nfrom CTFd.cache import cache\nfrom CTFd.utils import string_types\n\n\nclass ServerSentEvent(object):\n    def __init__(self, data, type=None, id=None):\n        self.data = data\n        self.type = type\n        self.id = id\n\n    def __str__(self):\n        if isinstance(self.data, string_types):\n            data = self.data\n        else:\n            data = json.dumps(self.data)\n        lines = [\"data:{value}\".format(value=line) for line in data.splitlines()]\n        if self.type:\n            lines.insert(0, \"event:{value}\".format(value=self.type))\n        if self.id:\n            lines.append(\"id:{value}\".format(value=self.id))\n        return \"\\n\".join(lines) + \"\\n\\n\"\n\n    def to_dict(self):\n        d = {\"data\": self.data}\n        if self.type:\n            d[\"type\"] = self.type\n        if self.id:\n            d[\"id\"] = self.id\n        return d\n\n\nclass EventManager(object):\n    def __init__(self):\n        self.clients = {}\n\n    def publish(self, data, type=None, channel=\"ctf\"):\n        event = ServerSentEvent(data, type=type)\n        message = event.to_dict()\n        for client in list(self.clients.values()):\n            client[channel].put(message)\n        return len(self.clients)\n\n    def listen(self):\n        pass\n\n    def subscribe(self, channel=\"ctf\"):\n        q = defaultdict(Queue)\n        self.clients[id(q)] = q\n        try:\n            # Immediately yield a ping event to force Response headers to be set\n            # or else some reverse proxies will incorrectly buffer SSE\n            yield ServerSentEvent(data=\"\", type=\"ping\")\n            while True:\n                try:\n                    with Timeout(5):\n                        message = q[channel].get()\n                        yield ServerSentEvent(**message)\n                except Timeout:\n                    yield ServerSentEvent(data=\"\", type=\"ping\")\n        finally:\n            del self.clients[id(q)]\n            del q\n\n\nclass RedisEventManager(EventManager):\n    def __init__(self):\n        super(EventManager, self).__init__()\n        self.client = cache.cache._write_client\n        self.clients = {}\n\n    def publish(self, data, type=None, channel=\"ctf\"):\n        event = ServerSentEvent(data, type=type)\n        message = json.dumps(event.to_dict())\n        return self.client.publish(message=message, channel=channel)\n\n    def listen(self, channel=\"ctf\"):\n        @retry(wait=wait_exponential(min=1, max=30))\n        def _listen():\n            while True:\n                pubsub = self.client.pubsub()\n                pubsub.subscribe(channel)\n                try:\n                    while True:\n                        message = pubsub.get_message(\n                            ignore_subscribe_messages=True, timeout=5\n                        )\n                        if message:\n                            if message[\"type\"] == \"message\":\n                                event = json.loads(message[\"data\"])\n                                for client in list(self.clients.values()):\n                                    client[channel].put(event)\n                finally:\n                    pubsub.close()\n\n        spawn(_listen)\n\n    def subscribe(self, channel=\"ctf\"):\n        q = defaultdict(Queue)\n        self.clients[id(q)] = q\n        try:\n            # Immediately yield a ping event to force Response headers to be set\n            # or else some reverse proxies will incorrectly buffer SSE\n            yield ServerSentEvent(data=\"\", type=\"ping\")\n            while True:\n                try:\n                    with Timeout(5):\n                        message = q[channel].get()\n                        yield ServerSentEvent(**message)\n                except Timeout:\n                    yield ServerSentEvent(data=\"\", type=\"ping\")\n        finally:\n            del self.clients[id(q)]\n            del q\n", "path": "CTFd/utils/events/__init__.py"}]}