But why the other two nodes couldn't accept connections?

2017-04-12T07:39:04.132922+02:00 cic-3 ceilometer-collector[8245]: 2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector [-] Dispatcher failed to handle the sample, requeue it.
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector Traceback (most recent call last):
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector   File "/usr/lib/python2.7/dist-packages/ceilometer/collector.py", line 156, in sample
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector     self.dispatcher_manager.map_method(self.method, samples)
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector   File "/usr/lib/python2.7/dist-packages/stevedore/extension.py", line 252, in map_method
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector     method_name, *args, **kwds)
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector   File "/usr/lib/python2.7/dist-packages/stevedore/extension.py", line 225, in map
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector     self._invoke_one_plugin(response.append, func, e, args, kwds)
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector   File "/usr/lib/python2.7/dist-packages/stevedore/extension.py", line 256, in _invoke_one_plugin
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector     response_callback(func(e, *args, **kwds))
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector   File "/usr/lib/python2.7/dist-packages/stevedore/extension.py", line 230, in _call_extension_method
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector     return getattr(extension.obj, method_name)(*args, **kwds)
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector   File "/usr/lib/python2.7/dist-packages/ceilometer/dispatcher/database.py", line 95, in record_metering_data
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector     self.meter_conn.record_metering_data(meter)
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector   File "/usr/lib/python2.7/dist-packages/ceilometer/storage/impl_mongodb.py", line 266, in record_metering_data
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector     return_document=pymongo.ReturnDocument.AFTER,
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector   File "/usr/lib/python2.7/dist-packages/ceilometer/storage/mongo/utils.py", line 415, in closure
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector     return call(*args, **kwargs)
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector   File "/usr/lib/python2.7/dist-packages/ceilometer/storage/mongo/utils.py", line 437, in __call__
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector     return self.method(*args, **kwargs)
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector   File "/usr/lib/python2.7/dist-packages/pymongo/collection.py", line 1881, in find_one_and_update
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector     sort, upsert, return_document, **kwargs)
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector   File "/usr/lib/python2.7/dist-packages/pymongo/collection.py", line 1689, in __find_and_modify
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector     with self._socket_for_writes() as sock_info:
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector   File "/usr/lib/python2.7/contextlib.py", line 17, in __enter__
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector     return self.gen.next()
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector   File "/usr/lib/python2.7/dist-packages/pymongo/mongo_client.py", line 663, in _get_socket
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector     server = self._get_topology().select_server(selector)
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector   File "/usr/lib/python2.7/dist-packages/pymongo/topology.py", line 121, in select_server
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector     address))
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector   File "/usr/lib/python2.7/dist-packages/pymongo/topology.py", line 97, in select_servers
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector     self._error_message(selector))
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector ServerSelectionTimeoutError: No primary available for writes
2017-04-12 07:39:04.130 8245 ERROR ceilometer.collector 
2017-04-12T07:39:04.388107+02:00 cic-3 ceilometer-collector[8246]: 2017-04-12 07:39:04.387 8246 WARNING ceilometer.storage.mongo.utils [-] Unable to reconnect to the primary mongodb: No primary available for writes. Trying again in 10 seconds.
2017-04-12T07:39:04.619904+02:00 cic-3 ceilometer-collector[8245]: 2017-04-12 07:39:04.619 8245 WARNING ceilometer.storage.mongo.utils [-] Unable to reconnect to the primary mongodb: No primary available for writes. Trying again in 10 seconds.