What happens if Proxies are up, Server is up, but Server has no DB connection?

[raphih18]

Hi all,

I have a question about how Zabbix behaves in a specific scenario involving Proxies.

Setup:

• Active agents send data to Proxies.
• Proxies also collect SNMP data.
• Both Zabbix Proxies are up and running.
• Zabbix Server process is up and running.
• However, the Zabbix Server temporarily has no database connection (e.g., during manual failover of our HA PostgreSQL setup).

My expectation:
Since the Proxies normally buffer data when the Server is down, I would assume they should also buffer data when the Server is up but cannot write to the DB. In other words, until the DB connection is restored (failover completed), all collected data should be stored locally on the Proxies and sent later.

Questions:

1. Is this actually how it works, or will the Proxies detect the issue differently?
2. Could there be data loss if the Server is running but DB connection is broken?
3. Is there any difference in behavior between active agent data and SNMP data in this situation?

Thanks in advance for any insights!
Raphael

[cyber]

Proxies have no knowledge about servers DB connection. So they keep gathering and sending as they should... If server does not accept it, they should retry.. and there is no difference is it agent data or snmp, as long as I understand it (and sometimes I don't... )
I think for a short period that server will survive without DB connection, depending how much it manages to cache (value cache). If it runs out of caches, you are screwed..

I have similar scenario every once in a while.. as hosts need patching, there is PG failovers etc... Usually there is no interruptions in work whatsover... some PG connect errors in log, but everything continues just fine...

[raphih18]

Hey cyber , thanks for your reply!
So, do I understand it correct that as long as the server can „cache“ the values sent to him from the proxies, he is able to write the values to the DB when the DB is available again? And after some time, the cache will get full and the proxies will know that and buffer it locally?

Do you have any knowledge on how long the server can cache the values? (dependent on the NVPS)

Thank you very much!

[cyber]

I don't really know, how long it can last... I never had such long interrupts.