prompt: We are currently solving the following issue within our repository. Here is the issue text:
  --- BEGIN ISSUE ---
  culler is failing and exiting when culling users and servers are slow to stop
  Two issues:
  
  1. culler script seems to exit when the cull request fails. It's unclear why this happens, but we should confirm and fix this
  2. the 'real' issue is that the culler is hitting 400 errors in the first place. The cause is servers that are slow to stop (DELETE /users/:name gives 400 if the user's server is running and cannot stop promptly). The previous request to stop the server will have returned 202 ACCEPTED instead of 204 DELETED in this case. If we delay deleting users if we get 202 ACCEPTED from the server deletion, we should be safe here.
  
  --- END ISSUE ---
  
  Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
  --- BEGIN FILES ---
  Path: `images/hub/cull_idle_servers.py`
  Content:
  ```
  1 #!/usr/bin/env python3
  2 # Imported from https://github.com/jupyterhub/jupyterhub/blob/0.8.0rc1/examples/cull-idle/cull_idle_servers.py
  3 """script to monitor and cull idle single-user servers
  4 
  5 Caveats:
  6 
  7 last_activity is not updated with high frequency,
  8 so cull timeout should be greater than the sum of:
  9 
  10 - single-user websocket ping interval (default: 30s)
  11 - JupyterHub.last_activity_interval (default: 5 minutes)
  12 
  13 You can run this as a service managed by JupyterHub with this in your config::
  14 
  15 
  16     c.JupyterHub.services = [
  17         {
  18             'name': 'cull-idle',
  19             'admin': True,
  20             'command': 'python cull_idle_servers.py --timeout=3600'.split(),
  21         }
  22     ]
  23 
  24 Or run it manually by generating an API token and storing it in `JUPYTERHUB_API_TOKEN`:
  25 
  26     export JUPYTERHUB_API_TOKEN=`jupyterhub token`
  27     python cull_idle_servers.py [--timeout=900] [--url=http://127.0.0.1:8081/hub/api]
  28 """
  29 
  30 import datetime
  31 import json
  32 import os
  33 
  34 from dateutil.parser import parse as parse_date
  35 
  36 from tornado.gen import coroutine
  37 from tornado.log import app_log
  38 from tornado.httpclient import AsyncHTTPClient, HTTPRequest
  39 from tornado.ioloop import IOLoop, PeriodicCallback
  40 from tornado.options import define, options, parse_command_line
  41 
  42 
  43 @coroutine
  44 def cull_idle(url, api_token, timeout, cull_users=False):
  45     """Shutdown idle single-user servers
  46 
  47     If cull_users, inactive *users* will be deleted as well.
  48     """
  49     auth_header = {
  50             'Authorization': 'token %s' % api_token
  51         }
  52     req = HTTPRequest(url=url + '/users',
  53         headers=auth_header,
  54     )
  55     now = datetime.datetime.utcnow()
  56     cull_limit = now - datetime.timedelta(seconds=timeout)
  57     client = AsyncHTTPClient()
  58     resp = yield client.fetch(req)
  59     users = json.loads(resp.body.decode('utf8', 'replace'))
  60     futures = []
  61 
  62     @coroutine
  63     def cull_one(user, last_activity):
  64         """cull one user"""
  65 
  66         # shutdown server first. Hub doesn't allow deleting users with running servers.
  67         if user['server']:
  68             app_log.info("Culling server for %s (inactive since %s)", user['name'], last_activity)
  69             req = HTTPRequest(url=url + '/users/%s/server' % user['name'],
  70                 method='DELETE',
  71                 headers=auth_header,
  72             )
  73             yield client.fetch(req)
  74         if cull_users:
  75             app_log.info("Culling user %s (inactive since %s)", user['name'], last_activity)
  76             req = HTTPRequest(url=url + '/users/%s' % user['name'],
  77                 method='DELETE',
  78                 headers=auth_header,
  79             )
  80             yield client.fetch(req)
  81 
  82     for user in users:
  83         if not user['server'] and not cull_users:
  84             # server not running and not culling users, nothing to do
  85             continue
  86         last_activity = parse_date(user['last_activity'])
  87         if last_activity < cull_limit:
  88             futures.append((user['name'], cull_one(user, last_activity)))
  89         else:
  90             app_log.debug("Not culling %s (active since %s)", user['name'], last_activity)
  91     
  92     for (name, f) in futures:
  93         yield f
  94         app_log.debug("Finished culling %s", name)
  95 
  96 
  97 if __name__ == '__main__':
  98     define('url', default=os.environ.get('JUPYTERHUB_API_URL'), help="The JupyterHub API URL")
  99     define('timeout', default=600, help="The idle timeout (in seconds)")
  100     define('cull_every', default=0, help="The interval (in seconds) for checking for idle servers to cull")
  101     define('cull_users', default=False,
  102         help="""Cull users in addition to servers.
  103                 This is for use in temporary-user cases such as tmpnb.""",
  104     )
  105     
  106     parse_command_line()
  107     if not options.cull_every:
  108         options.cull_every = options.timeout // 2
  109     api_token = os.environ['JUPYTERHUB_API_TOKEN']
  110     
  111     loop = IOLoop.current()
  112     cull = lambda : cull_idle(options.url, api_token, options.timeout, options.cull_users)
  113     # run once before scheduling periodic call
  114     loop.run_sync(cull)
  115     # schedule periodic cull
  116     pc = PeriodicCallback(cull, 1e3 * options.cull_every)
  117     pc.start()
  118     try:
  119         loop.start()
  120     except KeyboardInterrupt:
  121         pass
  122
  ```
  --- 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/images/hub/cull_idle_servers.py b/images/hub/cull_idle_servers.py
  --- a/images/hub/cull_idle_servers.py
  +++ b/images/hub/cull_idle_servers.py
  @@ -70,7 +70,15 @@
                   method='DELETE',
                   headers=auth_header,
               )
  -            yield client.fetch(req)
  +            resp = yield client.fetch(req)
  +            if resp.code == 202:
  +                msg = "Server for {} is slow to stop.".format(user['name'])
  +                if cull_users:
  +                    app_log.warning(msg + " Not culling user yet.")
  +                    # return here so we don't continue to cull the user
  +                    # which will fail if the server is still trying to shutdown
  +                    return
  +                app_log.warning(msg)
           if cull_users:
               app_log.info("Culling user %s (inactive since %s)", user['name'], last_activity)
               req = HTTPRequest(url=url + '/users/%s' % user['name'],
  @@ -83,12 +91,19 @@
           if not user['server'] and not cull_users:
               # server not running and not culling users, nothing to do
               continue
  +        if not user['last_activity']:
  +            continue
           last_activity = parse_date(user['last_activity'])
           if last_activity < cull_limit:
  +            # user might be in a transition (e.g. starting or stopping)
  +            # don't try to cull if this is happening
  +            if user['pending']:
  +                app_log.warning("Not culling user %s with pending %s", user['name'], user['pending'])
  +                continue
               futures.append((user['name'], cull_one(user, last_activity)))
           else:
               app_log.debug("Not culling %s (active since %s)", user['name'], last_activity)
  -    
  +
       for (name, f) in futures:
           yield f
           app_log.debug("Finished culling %s", name)
  @@ -102,16 +117,17 @@
           help="""Cull users in addition to servers.
                   This is for use in temporary-user cases such as tmpnb.""",
       )
  -    
  +
       parse_command_line()
       if not options.cull_every:
           options.cull_every = options.timeout // 2
       api_token = os.environ['JUPYTERHUB_API_TOKEN']
  -    
  +
       loop = IOLoop.current()
       cull = lambda : cull_idle(options.url, api_token, options.timeout, options.cull_users)
  -    # run once before scheduling periodic call
  -    loop.run_sync(cull)
  +    # schedule first cull immediately
  +    # because PeriodicCallback doesn't start until the end of the first interval
  +    loop.add_callback(cull)
       # schedule periodic cull
       pc = PeriodicCallback(cull, 1e3 * options.cull_every)
       pc.start()
  
verification_info: {"golden_diff": "diff --git a/images/hub/cull_idle_servers.py b/images/hub/cull_idle_servers.py\n--- a/images/hub/cull_idle_servers.py\n+++ b/images/hub/cull_idle_servers.py\n@@ -70,7 +70,15 @@\n                 method='DELETE',\n                 headers=auth_header,\n             )\n-            yield client.fetch(req)\n+            resp = yield client.fetch(req)\n+            if resp.code == 202:\n+                msg = \"Server for {} is slow to stop.\".format(user['name'])\n+                if cull_users:\n+                    app_log.warning(msg + \" Not culling user yet.\")\n+                    # return here so we don't continue to cull the user\n+                    # which will fail if the server is still trying to shutdown\n+                    return\n+                app_log.warning(msg)\n         if cull_users:\n             app_log.info(\"Culling user %s (inactive since %s)\", user['name'], last_activity)\n             req = HTTPRequest(url=url + '/users/%s' % user['name'],\n@@ -83,12 +91,19 @@\n         if not user['server'] and not cull_users:\n             # server not running and not culling users, nothing to do\n             continue\n+        if not user['last_activity']:\n+            continue\n         last_activity = parse_date(user['last_activity'])\n         if last_activity < cull_limit:\n+            # user might be in a transition (e.g. starting or stopping)\n+            # don't try to cull if this is happening\n+            if user['pending']:\n+                app_log.warning(\"Not culling user %s with pending %s\", user['name'], user['pending'])\n+                continue\n             futures.append((user['name'], cull_one(user, last_activity)))\n         else:\n             app_log.debug(\"Not culling %s (active since %s)\", user['name'], last_activity)\n-    \n+\n     for (name, f) in futures:\n         yield f\n         app_log.debug(\"Finished culling %s\", name)\n@@ -102,16 +117,17 @@\n         help=\"\"\"Cull users in addition to servers.\n                 This is for use in temporary-user cases such as tmpnb.\"\"\",\n     )\n-    \n+\n     parse_command_line()\n     if not options.cull_every:\n         options.cull_every = options.timeout // 2\n     api_token = os.environ['JUPYTERHUB_API_TOKEN']\n-    \n+\n     loop = IOLoop.current()\n     cull = lambda : cull_idle(options.url, api_token, options.timeout, options.cull_users)\n-    # run once before scheduling periodic call\n-    loop.run_sync(cull)\n+    # schedule first cull immediately\n+    # because PeriodicCallback doesn't start until the end of the first interval\n+    loop.add_callback(cull)\n     # schedule periodic cull\n     pc = PeriodicCallback(cull, 1e3 * options.cull_every)\n     pc.start()\n", "issue": "culler is failing and exiting when culling users and servers are slow to stop\nTwo issues:\r\n\r\n1. culler script seems to exit when the cull request fails. It's unclear why this happens, but we should confirm and fix this\r\n2. the 'real' issue is that the culler is hitting 400 errors in the first place. The cause is servers that are slow to stop (DELETE /users/:name gives 400 if the user's server is running and cannot stop promptly). The previous request to stop the server will have returned 202 ACCEPTED instead of 204 DELETED in this case. If we delay deleting users if we get 202 ACCEPTED from the server deletion, we should be safe here.\n", "before_files": [{"content": "#!/usr/bin/env python3\n# Imported from https://github.com/jupyterhub/jupyterhub/blob/0.8.0rc1/examples/cull-idle/cull_idle_servers.py\n\"\"\"script to monitor and cull idle single-user servers\n\nCaveats:\n\nlast_activity is not updated with high frequency,\nso cull timeout should be greater than the sum of:\n\n- single-user websocket ping interval (default: 30s)\n- JupyterHub.last_activity_interval (default: 5 minutes)\n\nYou can run this as a service managed by JupyterHub with this in your config::\n\n\n    c.JupyterHub.services = [\n        {\n            'name': 'cull-idle',\n            'admin': True,\n            'command': 'python cull_idle_servers.py --timeout=3600'.split(),\n        }\n    ]\n\nOr run it manually by generating an API token and storing it in `JUPYTERHUB_API_TOKEN`:\n\n    export JUPYTERHUB_API_TOKEN=`jupyterhub token`\n    python cull_idle_servers.py [--timeout=900] [--url=http://127.0.0.1:8081/hub/api]\n\"\"\"\n\nimport datetime\nimport json\nimport os\n\nfrom dateutil.parser import parse as parse_date\n\nfrom tornado.gen import coroutine\nfrom tornado.log import app_log\nfrom tornado.httpclient import AsyncHTTPClient, HTTPRequest\nfrom tornado.ioloop import IOLoop, PeriodicCallback\nfrom tornado.options import define, options, parse_command_line\n\n\n@coroutine\ndef cull_idle(url, api_token, timeout, cull_users=False):\n    \"\"\"Shutdown idle single-user servers\n\n    If cull_users, inactive *users* will be deleted as well.\n    \"\"\"\n    auth_header = {\n            'Authorization': 'token %s' % api_token\n        }\n    req = HTTPRequest(url=url + '/users',\n        headers=auth_header,\n    )\n    now = datetime.datetime.utcnow()\n    cull_limit = now - datetime.timedelta(seconds=timeout)\n    client = AsyncHTTPClient()\n    resp = yield client.fetch(req)\n    users = json.loads(resp.body.decode('utf8', 'replace'))\n    futures = []\n\n    @coroutine\n    def cull_one(user, last_activity):\n        \"\"\"cull one user\"\"\"\n\n        # shutdown server first. Hub doesn't allow deleting users with running servers.\n        if user['server']:\n            app_log.info(\"Culling server for %s (inactive since %s)\", user['name'], last_activity)\n            req = HTTPRequest(url=url + '/users/%s/server' % user['name'],\n                method='DELETE',\n                headers=auth_header,\n            )\n            yield client.fetch(req)\n        if cull_users:\n            app_log.info(\"Culling user %s (inactive since %s)\", user['name'], last_activity)\n            req = HTTPRequest(url=url + '/users/%s' % user['name'],\n                method='DELETE',\n                headers=auth_header,\n            )\n            yield client.fetch(req)\n\n    for user in users:\n        if not user['server'] and not cull_users:\n            # server not running and not culling users, nothing to do\n            continue\n        last_activity = parse_date(user['last_activity'])\n        if last_activity < cull_limit:\n            futures.append((user['name'], cull_one(user, last_activity)))\n        else:\n            app_log.debug(\"Not culling %s (active since %s)\", user['name'], last_activity)\n    \n    for (name, f) in futures:\n        yield f\n        app_log.debug(\"Finished culling %s\", name)\n\n\nif __name__ == '__main__':\n    define('url', default=os.environ.get('JUPYTERHUB_API_URL'), help=\"The JupyterHub API URL\")\n    define('timeout', default=600, help=\"The idle timeout (in seconds)\")\n    define('cull_every', default=0, help=\"The interval (in seconds) for checking for idle servers to cull\")\n    define('cull_users', default=False,\n        help=\"\"\"Cull users in addition to servers.\n                This is for use in temporary-user cases such as tmpnb.\"\"\",\n    )\n    \n    parse_command_line()\n    if not options.cull_every:\n        options.cull_every = options.timeout // 2\n    api_token = os.environ['JUPYTERHUB_API_TOKEN']\n    \n    loop = IOLoop.current()\n    cull = lambda : cull_idle(options.url, api_token, options.timeout, options.cull_users)\n    # run once before scheduling periodic call\n    loop.run_sync(cull)\n    # schedule periodic cull\n    pc = PeriodicCallback(cull, 1e3 * options.cull_every)\n    pc.start()\n    try:\n        loop.start()\n    except KeyboardInterrupt:\n        pass\n", "path": "images/hub/cull_idle_servers.py"}], "after_files": [{"content": "#!/usr/bin/env python3\n# Imported from https://github.com/jupyterhub/jupyterhub/blob/0.8.0rc1/examples/cull-idle/cull_idle_servers.py\n\"\"\"script to monitor and cull idle single-user servers\n\nCaveats:\n\nlast_activity is not updated with high frequency,\nso cull timeout should be greater than the sum of:\n\n- single-user websocket ping interval (default: 30s)\n- JupyterHub.last_activity_interval (default: 5 minutes)\n\nYou can run this as a service managed by JupyterHub with this in your config::\n\n\n    c.JupyterHub.services = [\n        {\n            'name': 'cull-idle',\n            'admin': True,\n            'command': 'python cull_idle_servers.py --timeout=3600'.split(),\n        }\n    ]\n\nOr run it manually by generating an API token and storing it in `JUPYTERHUB_API_TOKEN`:\n\n    export JUPYTERHUB_API_TOKEN=`jupyterhub token`\n    python cull_idle_servers.py [--timeout=900] [--url=http://127.0.0.1:8081/hub/api]\n\"\"\"\n\nimport datetime\nimport json\nimport os\n\nfrom dateutil.parser import parse as parse_date\n\nfrom tornado.gen import coroutine\nfrom tornado.log import app_log\nfrom tornado.httpclient import AsyncHTTPClient, HTTPRequest\nfrom tornado.ioloop import IOLoop, PeriodicCallback\nfrom tornado.options import define, options, parse_command_line\n\n\n@coroutine\ndef cull_idle(url, api_token, timeout, cull_users=False):\n    \"\"\"Shutdown idle single-user servers\n\n    If cull_users, inactive *users* will be deleted as well.\n    \"\"\"\n    auth_header = {\n            'Authorization': 'token %s' % api_token\n        }\n    req = HTTPRequest(url=url + '/users',\n        headers=auth_header,\n    )\n    now = datetime.datetime.utcnow()\n    cull_limit = now - datetime.timedelta(seconds=timeout)\n    client = AsyncHTTPClient()\n    resp = yield client.fetch(req)\n    users = json.loads(resp.body.decode('utf8', 'replace'))\n    futures = []\n\n    @coroutine\n    def cull_one(user, last_activity):\n        \"\"\"cull one user\"\"\"\n\n        # shutdown server first. Hub doesn't allow deleting users with running servers.\n        if user['server']:\n            app_log.info(\"Culling server for %s (inactive since %s)\", user['name'], last_activity)\n            req = HTTPRequest(url=url + '/users/%s/server' % user['name'],\n                method='DELETE',\n                headers=auth_header,\n            )\n            resp = yield client.fetch(req)\n            if resp.code == 202:\n                msg = \"Server for {} is slow to stop.\".format(user['name'])\n                if cull_users:\n                    app_log.warning(msg + \" Not culling user yet.\")\n                    # return here so we don't continue to cull the user\n                    # which will fail if the server is still trying to shutdown\n                    return\n                app_log.warning(msg)\n        if cull_users:\n            app_log.info(\"Culling user %s (inactive since %s)\", user['name'], last_activity)\n            req = HTTPRequest(url=url + '/users/%s' % user['name'],\n                method='DELETE',\n                headers=auth_header,\n            )\n            yield client.fetch(req)\n\n    for user in users:\n        if not user['server'] and not cull_users:\n            # server not running and not culling users, nothing to do\n            continue\n        if not user['last_activity']:\n            continue\n        last_activity = parse_date(user['last_activity'])\n        if last_activity < cull_limit:\n            # user might be in a transition (e.g. starting or stopping)\n            # don't try to cull if this is happening\n            if user['pending']:\n                app_log.warning(\"Not culling user %s with pending %s\", user['name'], user['pending'])\n                continue\n            futures.append((user['name'], cull_one(user, last_activity)))\n        else:\n            app_log.debug(\"Not culling %s (active since %s)\", user['name'], last_activity)\n\n    for (name, f) in futures:\n        yield f\n        app_log.debug(\"Finished culling %s\", name)\n\n\nif __name__ == '__main__':\n    define('url', default=os.environ.get('JUPYTERHUB_API_URL'), help=\"The JupyterHub API URL\")\n    define('timeout', default=600, help=\"The idle timeout (in seconds)\")\n    define('cull_every', default=0, help=\"The interval (in seconds) for checking for idle servers to cull\")\n    define('cull_users', default=False,\n        help=\"\"\"Cull users in addition to servers.\n                This is for use in temporary-user cases such as tmpnb.\"\"\",\n    )\n\n    parse_command_line()\n    if not options.cull_every:\n        options.cull_every = options.timeout // 2\n    api_token = os.environ['JUPYTERHUB_API_TOKEN']\n\n    loop = IOLoop.current()\n    cull = lambda : cull_idle(options.url, api_token, options.timeout, options.cull_users)\n    # schedule first cull immediately\n    # because PeriodicCallback doesn't start until the end of the first interval\n    loop.add_callback(cull)\n    # schedule periodic cull\n    pc = PeriodicCallback(cull, 1e3 * options.cull_every)\n    pc.start()\n    try:\n        loop.start()\n    except KeyboardInterrupt:\n        pass\n", "path": "images/hub/cull_idle_servers.py"}]}