Steps to reproduce:

1. Run 4 or more concurrent Zabbix clients (same user id/ password) from different forked processes
2. When one of them finishes before the other, session is invalidated on server side and causes an exception on the other clients

To get a new session:

 def get_zabbix_api(self):
"""
Get a Zabbix session
:return: ZabbixAPI instance
"""
return ZabbixAPI(url=self.url, user=self.user, password=self.password) 

To close the session:

if zapi is not None:
zapi.user.logout() 

Result:

pyzabbix.api.ZabbixAPIException: {'code': -32500, 'message': 'Application error.', 'data': 'SQL statement execution has failed "DELETE FROM sessions WHERE status=\'1\' AND userid=\'71\'"', 'json': "{'jsonrpc': '2.0', 'method': 'user.logout', 'params': {}, 'id': '1', 'auth': '********'}"} 

Expected:
Each session should stay alive regardless if other sessions are active. To be clear, this is not a multi threaded application but 4 or more different scripts running different get_history methods.