Zabbix proxy ignores DataSenderFrequency

Steps to reproduce:

1. Setup zabbix active proxy
2. set DataSenderFrequency=10 in zabbix_proxy.conf

Result:

Proxy sends data roughly every second - sleeps exactly 1s between seding, often sending exactly 0 items, generating unnecessary traffic.

Expected:

Proxy sleeps 10s.

Description

Issue affects zabbix-proxy 3.4.12. I haven't verified newer versions of proxy, but source on svn://svn.zabbix.com/trunk/src/zabbix_proxy/datasender/datasender.c seems affected.

In ZBX_THREAD_ENTRY(datasender_thread), it updates proctitle as ".. idle $CONFIG_PROXYDATA_FREQUENCY sec", but sleeps only for ZBX_TASK_UPDATE_FREQUENCY (constant 1), and then goes on again to "sending data".

It seems to me, it should sleep CONFIG_PROXYDATA_FREQUENCY.

 
References:

I have searched for relevant bug reports and only found 2 semi-relevant.

One a seemingly misguided request that was rejected.
https://support.zabbix.com/browse/ZBX-9219

Change in the second one might have introduced the bug.
https://support.zabbix.com/browse/ZBX-12668