Jenkins can't start after April release

Hi,

I’m using Jenkins LTS with version 2.401.3 on AWS EKS version 1.28.
It was running fine and works properly until Jenkins release 2.440.3 (2024-04-17).

I was restarting Jenkins every couple of days, as part of some tests we do, so last time I restarted Jenkins 2.401.3, was on April 16th with no issues, and on April 19th Jenkins couldn’t came up and no informative logs were found except the following from jcasc-reload container.
I changed lots of configurations including startupProbe but nothing fixed the issues until upgrading the from 2.401.3 to 2.440.3.

Can you please assist here and provide guidance or root cause of why the issue happened?
below is the full logs on the jcasc container, no errors were found on init, Jenkins or any other containers.

kubectl logs -f jenkins-0 -n jenkins-qa-stg -c config-reload
[2024-04-25 11:03:35] Starting collector
[2024-04-25 11:03:35] No folder annotation was provided, defaulting to k8s-sidecar-target-directory
[2024-04-25 11:03:35] Selected resource type: ('configmap',)
[2024-04-25 11:03:35] Loading incluster config ...
[2024-04-25 11:03:35] Config for cluster api at 'https://172.20.0.1:443' loaded...
[2024-04-25 11:03:35] Unique filenames will not be enforced.
[2024-04-25 11:03:35] 5xx response content will not be enabled.
[2024-04-25 11:03:40] Working on ADDED configmap jenkins-qa-stg/jenkins-jenkins-config-freestyle-jobs
[2024-04-25 11:04:19] Received unknown exception: HTTPConnectionPool(host='localhost', port=8080): Max retries exceeded with url: /reload-configuration-as-code/?casc-reload-token=jenkins-0 (Caused by ResponseError('too many 503 error responses'))

Traceback (most recent call last):
 File "/usr/local/lib/python3.8/site-packages/requests/adapters.py", line 439, in send
   resp = conn.urlopen(
 File "/usr/local/lib/python3.8/site-packages/urllib3/connectionpool.py", line 846, in urlopen
   return self.urlopen(
 File "/usr/local/lib/python3.8/site-packages/urllib3/connectionpool.py", line 846, in urlopen
   return self.urlopen(
 File "/usr/local/lib/python3.8/site-packages/urllib3/connectionpool.py", line 846, in urlopen
   return self.urlopen(
 [Previous line repeated 2 more times]
 File "/usr/local/lib/python3.8/site-packages/urllib3/connectionpool.py", line 836, in urlopen
   retries = retries.increment(method, url, response=response, _pool=self)
 File "/usr/local/lib/python3.8/site-packages/urllib3/util/retry.py", line 574, in increment
   raise MaxRetryError(_pool, url, error or ResponseError(cause))
urllib3.exceptions.MaxRetryError: HTTPConnectionPool(host='localhost', port=8080): Max retries exceeded with url: /reload-configuration-as-code/?casc-reload-token=jenkins-0 (Caused by ResponseError('too many 503 error responses'))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
 File "/app/resources.py", line 239, in _watch_resource_loop
   _watch_resource_iterator(*args)
 File "/app/resources.py", line 227, in _watch_resource_iterator
   request(request_url, request_method, enable_5xx, request_payload)
 File "/app/helpers.py", line 123, in request
   res = r.post("%s" % url, auth=auth, json=payload, timeout=REQ_TIMEOUT)
 File "/usr/local/lib/python3.8/site-packages/requests/sessions.py", line 590, in post
   return self.request('POST', url, data=data, json=json, **kwargs)
 File "/usr/local/lib/python3.8/site-packages/requests/sessions.py", line 542, in request
   resp = self.send(prep, **send_kwargs)
 File "/usr/local/lib/python3.8/site-packages/requests/sessions.py", line 655, in send
   r = adapter.send(request, **kwargs)
 File "/usr/local/lib/python3.8/site-packages/requests/adapters.py", line 507, in send
   raise RetryError(e, request=request)
requests.exceptions.RetryError: HTTPConnectionPool(host='localhost', port=8080): Max retries exceeded with url: /reload-configuration-as-code/?casc-reload-token=jenkins-0 (Caused by ResponseError('too many 503 error responses'))
[2024-04-25 11:04:24] Working on ADDED configmap jenkins-qa-stg/jenkins-jenkins-config-freestyle-jobs
[2024-04-25 11:04:24] Contents of freestyle-jobs.yaml haven't changed. Not overwriting existing file
[2024-04-25 11:04:24] Working on ADDED configmap jenkins-qa-stg/jenkins-jenkins-config-jenkins-casc-configs
[2024-04-25 11:04:57] Received unknown exception: HTTPConnectionPool(host='localhost', port=8080): Max retries exceeded with url: /reload-configuration-as-code/?casc-reload-token=jenkins-0 (Caused by ResponseError('too many 503 error responses'))

Traceback (most recent call last):
 File "/usr/local/lib/python3.8/site-packages/requests/adapters.py", line 439, in send
   resp = conn.urlopen(
 File "/usr/local/lib/python3.8/site-packages/urllib3/connectionpool.py", line 846, in urlopen
   return self.urlopen(
 File "/usr/local/lib/python3.8/site-packages/urllib3/connectionpool.py", line 846, in urlopen
   return self.urlopen(
 File "/usr/local/lib/python3.8/site-packages/urllib3/connectionpool.py", line 846, in urlopen
   return self.urlopen(
 [Previous line repeated 2 more times]
 File "/usr/local/lib/python3.8/site-packages/urllib3/connectionpool.py", line 836, in urlopen
   retries = retries.increment(method, url, response=response, _pool=self)
 File "/usr/local/lib/python3.8/site-packages/urllib3/util/retry.py", line 574, in increment
   raise MaxRetryError(_pool, url, error or ResponseError(cause))
urllib3.exceptions.MaxRetryError: HTTPConnectionPool(host='localhost', port=8080): Max retries exceeded with url: /reload-configuration-as-code/?casc-reload-token=jenkins-0 (Caused by ResponseError('too many 503 error responses'))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
 File "/app/resources.py", line 239, in _watch_resource_loop
   _watch_resource_iterator(*args)
 File "/app/resources.py", line 227, in _watch_resource_iterator
   request(request_url, request_method, enable_5xx, request_payload)
 File "/app/helpers.py", line 123, in request
   res = r.post("%s" % url, auth=auth, json=payload, timeout=REQ_TIMEOUT)
 File "/usr/local/lib/python3.8/site-packages/requests/sessions.py", line 590, in post
   return self.request('POST', url, data=data, json=json, **kwargs)
 File "/usr/local/lib/python3.8/site-packages/requests/sessions.py", line 542, in request
   resp = self.send(prep, **send_kwargs)
 File "/usr/local/lib/python3.8/site-packages/requests/sessions.py", line 655, in send
   r = adapter.send(request, **kwargs)
 File "/usr/local/lib/python3.8/site-packages/requests/adapters.py", line 507, in send
   raise RetryError(e, request=request)
requests.exceptions.RetryError: HTTPConnectionPool(host='localhost', port=8080): Max retries exceeded with url: /reload-configuration-as-code/?casc-reload-token=jenkins-0 (Caused by ResponseError('too many 503 error responses'))
[2024-04-25 11:05:02] Working on ADDED configmap jenkins-qa-stg/jenkins-jenkins-config-freestyle-jobs
[2024-04-25 11:05:02] Contents of freestyle-jobs.yaml haven't changed. Not overwriting existing file
[2024-04-25 11:05:02] Working on ADDED configmap jenkins-qa-stg/jenkins-jenkins-config-jenkins-casc-configs
[2024-04-25 11:05:02] Contents of jenkins-casc-configs.yaml haven't changed. Not overwriting existing file
[2024-04-25 11:05:02] Working on ADDED configmap jenkins-qa-stg/jenkins-jenkins-jcasc-config
[2024-04-25 11:05:36] Received unknown exception: HTTPConnectionPool(host='localhost', port=8080): Max retries exceeded with url: /reload-configuration-as-code/?casc-reload-token=jenkins-0 (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7f8263cbc1f0>: Failed to establish a new connection: [Errno 111] Connection refused'))

Traceback (most recent call last):
 File "/usr/local/lib/python3.8/site-packages/urllib3/connection.py", line 174, in _new_conn
   conn = connection.create_connection(
 File "/usr/local/lib/python3.8/site-packages/urllib3/util/connection.py", line 96, in create_connection
   raise err
 File "/usr/local/lib/python3.8/site-packages/urllib3/util/connection.py", line 86, in create_connection
   sock.connect(sa)
ConnectionRefusedError: [Errno 111] Connection refused

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
 File "/usr/local/lib/python3.8/site-packages/urllib3/connectionpool.py", line 699, in urlopen
   httplib_response = self._make_request(
 File "/usr/local/lib/python3.8/site-packages/urllib3/connectionpool.py", line 394, in _make_request
   conn.request(method, url, **httplib_request_kw)
 File "/usr/local/lib/python3.8/site-packages/urllib3/connection.py", line 239, in request
   super(HTTPConnection, self).request(method, url, body=body, headers=headers)
 File "/usr/local/lib/python3.8/http/client.py", line 1256, in request
   self._send_request(method, url, body, headers, encode_chunked)
 File "/usr/local/lib/python3.8/http/client.py", line 1302, in _send_request
   self.endheaders(body, encode_chunked=encode_chunked)
 File "/usr/local/lib/python3.8/http/client.py", line 1251, in endheaders
   self._send_output(message_body, encode_chunked=encode_chunked)
 File "/usr/local/lib/python3.8/http/client.py", line 1011, in _send_output
   self.send(msg)
 File "/usr/local/lib/python3.8/http/client.py", line 951, in send
   self.connect()
 File "/usr/local/lib/python3.8/site-packages/urllib3/connection.py", line 205, in connect
   conn = self._new_conn()
 File "/usr/local/lib/python3.8/site-packages/urllib3/connection.py", line 186, in _new_conn
   raise NewConnectionError(
urllib3.exceptions.NewConnectionError: <urllib3.connection.HTTPConnection object at 0x7f8263cbc1f0>: Failed to establish a new connection: [Errno 111] Connection refused

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
 File "/usr/local/lib/python3.8/site-packages/requests/adapters.py", line 439, in send
   resp = conn.urlopen(
 File "/usr/local/lib/python3.8/site-packages/urllib3/connectionpool.py", line 846, in urlopen
   return self.urlopen(
 File "/usr/local/lib/python3.8/site-packages/urllib3/connectionpool.py", line 846, in urlopen
   return self.urlopen(
 File "/usr/local/lib/python3.8/site-packages/urllib3/connectionpool.py", line 846, in urlopen
   return self.urlopen(
 [Previous line repeated 2 more times]
 File "/usr/local/lib/python3.8/site-packages/urllib3/connectionpool.py", line 755, in urlopen
   retries = retries.increment(
 File "/usr/local/lib/python3.8/site-packages/urllib3/util/retry.py", line 574, in increment
   raise MaxRetryError(_pool, url, error or ResponseError(cause))
urllib3.exceptions.MaxRetryError: HTTPConnectionPool(host='localhost', port=8080): Max retries exceeded with url: /reload-configuration-as-code/?casc-reload-token=jenkins-0 (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7f8263cbc1f0>: Failed to establish a new connection: [Errno 111] Connection refused'))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
 File "/app/resources.py", line 239, in _watch_resource_loop
   _watch_resource_iterator(*args)
 File "/app/resources.py", line 227, in _watch_resource_iterator
   request(request_url, request_method, enable_5xx, request_payload)
 File "/app/helpers.py", line 123, in request
   res = r.post("%s" % url, auth=auth, json=payload, timeout=REQ_TIMEOUT)
 File "/usr/local/lib/python3.8/site-packages/requests/sessions.py", line 590, in post
   return self.request('POST', url, data=data, json=json, **kwargs)
 File "/usr/local/lib/python3.8/site-packages/requests/sessions.py", line 542, in request
   resp = self.send(prep, **send_kwargs)
 File "/usr/local/lib/python3.8/site-packages/requests/sessions.py", line 655, in send
   r = adapter.send(request, **kwargs)
 File "/usr/local/lib/python3.8/site-packages/requests/adapters.py", line 516, in send
   raise ConnectionError(e, request=request)
requests.exceptions.ConnectionError: HTTPConnectionPool(host='localhost', port=8080): Max retries exceeded with url: /reload-configuration-as-code/?casc-reload-token=jenkins-0 (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7f8263cbc1f0>: Failed to establish a new connection: [Errno 111] Connection refused'))
[2024-04-25 11:05:41] Working on ADDED configmap jenkins-qa-stg/jenkins-jenkins-config-freestyle-jobs
[2024-04-25 11:05:41] Contents of freestyle-jobs.yaml haven't changed. Not overwriting existing file
[2024-04-25 11:05:41] Working on ADDED configmap jenkins-qa-stg/jenkins-jenkins-config-jenkins-casc-configs
[2024-04-25 11:05:41] Contents of jenkins-casc-configs.yaml haven't changed. Not overwriting existing file
[2024-04-25 11:05:41] Working on ADDED configmap jenkins-qa-stg/jenkins-jenkins-jcasc-config
[2024-04-25 11:05:41] Contents of jcasc-default-config.yaml haven't changed. Not overwriting existing file
[2024-04-25 11:06:46] Working on ADDED configmap jenkins-qa-stg/jenkins-jenkins-config-freestyle-jobs
[2024-04-25 11:06:46] Contents of freestyle-jobs.yaml haven't changed. Not overwriting existing file
[2024-04-25 11:06:46] Working on ADDED configmap jenkins-qa-stg/jenkins-jenkins-config-jenkins-casc-configs
[2024-04-25 11:06:46] Contents of jenkins-casc-configs.yaml haven't changed. Not overwriting existing file
[2024-04-25 11:06:46] Working on ADDED configmap jenkins-qa-stg/jenkins-jenkins-jcasc-config
[2024-04-25 11:06:46] Contents of jcasc-default-config.yaml haven't changed. Not overwriting existing file
[2024-04-25 11:07:51] Working on ADDED configmap jenkins-qa-stg/jenkins-jenkins-config-freestyle-jobs
[2024-04-25 11:07:51] Contents of freestyle-jobs.yaml haven't changed. Not overwriting existing file
[2024-04-25 11:07:51] Working on ADDED configmap jenkins-qa-stg/jenkins-jenkins-config-jenkins-casc-configs
[2024-04-25 11:07:51] Contents of jenkins-casc-configs.yaml haven't changed. Not overwriting existing file
[2024-04-25 11:07:51] Working on ADDED configmap jenkins-qa-stg/jenkins-jenkins-jcasc-config
[2024-04-25 11:07:51] Contents of jcasc-default-config.yaml haven't changed. Not overwriting existing file
[2024-04-25 11:08:56] Working on ADDED configmap jenkins-qa-stg/jenkins-jenkins-config-freestyle-jobs
[2024-04-25 11:08:56] Contents of freestyle-jobs.yaml haven't changed. Not overwriting existing file
[2024-04-25 11:08:56] Working on ADDED configmap jenkins-qa-stg/jenkins-jenkins-config-jenkins-casc-configs
[2024-04-25 11:08:56] Contents of jenkins-casc-configs.yaml haven't changed. Not overwriting existing file
[2024-04-25 11:08:56] Working on ADDED configmap jenkins-qa-stg/jenkins-jenkins-jcasc-config
[2024-04-25 11:08:56] Contents of jcasc-default-config.yaml haven't changed. Not overwriting existing file
[2024-04-25 11:10:01] Working on ADDED configmap jenkins-qa-stg/jenkins-jenkins-config-freestyle-jobs
[2024-04-25 11:10:01] Contents of freestyle-jobs.yaml haven't changed. Not overwriting existing file
[2024-04-25 11:10:01] Working on ADDED configmap jenkins-qa-stg/jenkins-jenkins-config-jenkins-casc-configs
[2024-04-25 11:10:01] Contents of jenkins-casc-configs.yaml haven't changed. Not overwriting existing file
[2024-04-25 11:10:01] Working on ADDED configmap jenkins-qa-stg/jenkins-jenkins-jcasc-config
[2024-04-25 11:10:01] Contents of jcasc-default-config.yaml haven't changed. Not overwriting existing file