I will report a problem about unique constraint violation in sessions table of Zabbix database in version 2.0.4.

One of our customers found the messages below in /var/log/messages of Zabbix server;
cf. original messages are Japanese, so I translated them.

Jul 8 13:18:25 ZXMGH01Z postgres[17438]: [3-1] ERROR: duplicate key "sessions_pkey" violates unique constrain.
Jul 8 13:18:25 ZXMGH01Z postgres[17438]: [3-2] statement: INSERT INTO sessions (sessionid,userid,lastaccess,status) VALUES ('48839fe8afeb64567fcfbd8778a4e8e4',1,1436329105,0)

It looks that only frontend uses "INSERT INTO sessions" statement when users log on to frontend. The customer said that he didn't find errors in frontend.

I checked this forum but I couldn't find same kind of problem.

Is this a bug? If no, in what situations does this happen?

Thank you.