Zabbix agent fails to reconnect after server restart.

[Roe]

Agent is installed on windows 2016 server.
Agent version v5.0.3
Zabbix server 5.0.3



if the zabbix-server service is down for more than 60 sec +, agent fails to reconnect.
Other active agents on other servers seems ok.



From loglevel 3

started to fail ()
3796:20200904:125530.577 cannot parse list of active checks: cannot find pair with name "regexp"

From loglevel 5

9128:20200904:132519.990 NOT OK
2728:20200904:132529.853 In collect_perfstat()
2728:20200904:132529.855 End of collect_perfstat()
2728:20200904:132530.856 In collect_perfstat()
2728:20200904:132530.857 End of collect_perfstat()
9128:20200904:132531.249 send value error: [recv] ZBX_TCP_READ() failed: [0x0000274C] A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.
9128:20200904:132531.250 End of send_buffer():FAIL
9128:20200904:132531.250 In process_active_checks() server:'' port:
9128:20200904:132531.251 for key [agent.ping] received value [1]
9128:20200904:132531.251 In process_value() key:':agent.ping' lastlogsize:null value:'1'
9128:20200904:132531.252 In send_buffer() host:'' port: entries:100/100

9128:20200904:132531.256 JSON before sending [{"request":"agent data","session":"

2728:20200904:132531.859 In collect_perfstat()
2728:20200904:132531.860 End of collect_perfstat()
2728:20200904:132532.862 In collect_perfstat()
2728:20200904:132532.863 End of collect_perfstat()
2728:20200904:132533.865 In collect_perfstat()
2728:20200904:132533.866 End of collect_perfstat()


From zabbix-server log

agent.ping.nodata(30)": item does not have enough data after server start or item creation.".

[Ryan3]

Now, imagine that you intend to set up automatic issue resolution on your hosts in addition to monitoring. The simplest example with Windows services would be configuring the items and triggers to check the health of specific services. But before notifying users about a Windows service that has stopped, you want to try to restart it automatically.

[Roe]

Ok, I solved the problem, but I'm not sure why other agents work on other windows installations.
The problem is BufferSize in zabbix_agentd.conf, default it's set to 100.

It looks like the agent crashes after approximately 50.
Setting BufferSize=2 solved the problem.