The Kernel team experienced this problem yesterday, Feb 15th.  
MAAS Version: MAAS version: 2.9.2 (9164-g.ac176b5c4-0ubuntu1~20.04.1)
Deb Pkg Installation

Here are the logs from the rackd controller at the time this occurred.
There were no obvious warnings/errors/tracebacks in the regiond.log
I restarted maas-rackd and maas-regiond services / updated the boot sources and the problem appears to have resolved itself.  Yet, would be nice to know why this happened to begin with.


2022-02-15 15:31:44 provisioningserver.rpc.clusterservice: [critical] Failed to contact region. (While requesting RPC info at http://10.246.72.3:5240/MAAS).
	Traceback (most recent call last):
	  File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 460, in callback
	    self._startRunCallbacks(result)
	  File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 568, in _startRunCallbacks
	    self._runCallbacks()
	  File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 654, in _runCallbacks
	    current.result = callback(current.result, *args, **kw)
	  File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 1475, in gotResult
	    _inlineCallbacks(r, g, status)
	--- <exception caught here> ---
	  File "/usr/lib/python3/dist-packages/provisioningserver/rpc/clusterservice.py", line 1367, in _doUpdate
	    eventloops, maas_url = yield self._get_rpc_info(urls)
	  File "/usr/lib/python3/dist-packages/provisioningserver/rpc/clusterservice.py", line 1631, in _get_rpc_info
	    raise config_exc
	  File "/usr/lib/python3/dist-packages/provisioningserver/rpc/clusterservice.py", line 1602, in _get_rpc_info
	    eventloops, maas_url = yield self._parallel_fetch_rpc_info(urls)
	  File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 654, in _runCallbacks
	    current.result = callback(current.result, *args, **kw)
	  File "/usr/lib/python3/dist-packages/provisioningserver/rpc/clusterservice.py", line 1576, in handle_responses
	    errors[0].raiseException()
	  File "/usr/lib/python3/dist-packages/twisted/python/failure.py", line 467, in raiseException
	    raise self.value.with_traceback(self.tb)
	  File "/usr/lib/python3/dist-packages/provisioningserver/rpc/clusterservice.py", line 1537, in _serial_fetch_rpc_info
	    raise last_exc
	  File "/usr/lib/python3/dist-packages/provisioningserver/rpc/clusterservice.py", line 1529, in _serial_fetch_rpc_info
	    response = yield self._fetch_rpc_info(url, orig_url)
	  File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 1416, in _inlineCallbacks
	    result = result.throwExceptionIntoGenerator(g)
	  File "/usr/lib/python3/dist-packages/twisted/python/failure.py", line 491, in throwExceptionIntoGenerator
	    return g.throw(self.type, self.value, self.tb)
	  File "/usr/lib/python3/dist-packages/provisioningserver/rpc/clusterservice.py", line 1631, in _get_rpc_info
	    raise config_exc
	  File "/usr/lib/python3/dist-packages/provisioningserver/rpc/clusterservice.py", line 1602, in _get_rpc_info
	    eventloops, maas_url = yield self._parallel_fetch_rpc_info(urls)
	  File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 654, in _runCallbacks
	    current.result = callback(current.result, *args, **kw)
	  File "/usr/lib/python3/dist-packages/provisioningserver/rpc/clusterservice.py", line 1576, in handle_responses
	    errors[0].raiseException()
	  File "/usr/lib/python3/dist-packages/twisted/python/failure.py", line 467, in raiseException
	    raise self.value.with_traceback(self.tb)
	  File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 1416, in _inlineCallbacks
	    result = result.throwExceptionIntoGenerator(g)
	  File "/usr/lib/python3/dist-packages/twisted/python/failure.py", line 491, in throwExceptionIntoGenerator
	    return g.throw(self.type, self.value, self.tb)
	  File "/usr/lib/python3/dist-packages/provisioningserver/rpc/clusterservice.py", line 1537, in _serial_fetch_rpc_info
	    raise last_exc
	  File "/usr/lib/python3/dist-packages/provisioningserver/rpc/clusterservice.py", line 1529, in _serial_fetch_rpc_info
	    response = yield self._fetch_rpc_info(url, orig_url)
	twisted.internet.error.ConnectingCancelledError: HostnameAddress(hostname=b'10.246.72.3', port=5240)
	
2022-02-15 15:33:39 provisioningserver.rpc.clusterservice: [critical] Failed to contact region. (While requesting RPC info at http://10.246.72.3:5240/MAAS).
	Traceback (most recent call last):
	  File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 460, in callback
	    self._startRunCallbacks(result)
	  File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 568, in _startRunCallbacks
	    self._runCallbacks()
	  File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 654, in _runCallbacks
	    current.result = callback(current.result, *args, **kw)
	  File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 1475, in gotResult
	    _inlineCallbacks(r, g, status)
	--- <exception caught here> ---
	  File "/usr/lib/python3/dist-packages/provisioningserver/rpc/clusterservice.py", line 1367, in _doUpdate
	    eventloops, maas_url = yield self._get_rpc_info(urls)
	  File "/usr/lib/python3/dist-packages/provisioningserver/rpc/clusterservice.py", line 1631, in _get_rpc_info
	    raise config_exc
	  File "/usr/lib/python3/dist-packages/provisioningserver/rpc/clusterservice.py", line 1602, in _get_rpc_info
	    eventloops, maas_url = yield self._parallel_fetch_rpc_info(urls)
	  File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 654, in _runCallbacks
	    current.result = callback(current.result, *args, **kw)
	  File "/usr/lib/python3/dist-packages/provisioningserver/rpc/clusterservice.py", line 1576, in handle_responses
	    errors[0].raiseException()
	  File "/usr/lib/python3/dist-packages/twisted/python/failure.py", line 467, in raiseException
	    raise self.value.with_traceback(self.tb)
	  File "/usr/lib/python3/dist-packages/provisioningserver/rpc/clusterservice.py", line 1537, in _serial_fetch_rpc_info
	    raise last_exc
	  File "/usr/lib/python3/dist-packages/provisioningserver/rpc/clusterservice.py", line 1529, in _serial_fetch_rpc_info
	    response = yield self._fetch_rpc_info(url, orig_url)
	  File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 1416, in _inlineCallbacks
	    result = result.throwExceptionIntoGenerator(g)
	  File "/usr/lib/python3/dist-packages/twisted/python/failure.py", line 491, in throwExceptionIntoGenerator
	    return g.throw(self.type, self.value, self.tb)
	  File "/usr/lib/python3/dist-packages/provisioningserver/rpc/clusterservice.py", line 1631, in _get_rpc_info
	    raise config_exc
	  File "/usr/lib/python3/dist-packages/provisioningserver/rpc/clusterservice.py", line 1602, in _get_rpc_info
	    eventloops, maas_url = yield self._parallel_fetch_rpc_info(urls)
	  File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 654, in _runCallbacks
	    current.result = callback(current.result, *args, **kw)
	  File "/usr/lib/python3/dist-packages/provisioningserver/rpc/clusterservice.py", line 1576, in handle_responses
	    errors[0].raiseException()
	  File "/usr/lib/python3/dist-packages/twisted/python/failure.py", line 467, in raiseException
	    raise self.value.with_traceback(self.tb)
	  File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 1416, in _inlineCallbacks
	    result = result.throwExceptionIntoGenerator(g)
	  File "/usr/lib/python3/dist-packages/twisted/python/failure.py", line 491, in throwExceptionIntoGenerator
	    return g.throw(self.type, self.value, self.tb)
	  File "/usr/lib/python3/dist-packages/provisioningserver/rpc/clusterservice.py", line 1537, in _serial_fetch_rpc_info
	    raise last_exc
	  File "/usr/lib/python3/dist-packages/provisioningserver/rpc/clusterservice.py", line 1529, in _serial_fetch_rpc_info
	    response = yield self._fetch_rpc_info(url, orig_url)
	twisted.internet.error.ConnectingCancelledError: HostnameAddress(hostname=b'10.246.72.3', port=5240)