Another blog post here with some common errors. This should help new folks who are using Zabbix to monitor your apps or infrastructure.
These errors are specific to version 2.x - 3.x. But many of the error messages will be the same on newer versions as well.
cannot connect to [[10.1.3.143]:10052]:  Connection refused
Zabbix cannot reach the java gateway. Make sure it is running.
Get value from agent failed: ZBX_TCP_READ() failed:  Connection reset by peer
First you should check that ports are open between Zabbix server and target host. The Zabbix server will try to connect to a Zabbix agent on port 10051 by default.
This can happen even though ports are open though. The issue here is that the agent running on the target host is not accepting connection from the Zabbix server because server's IP is not under Server key in agent configuration file.
Received empty response from Zabbix Agent at [10.1.2.242]. Assuming that agent dropped connection because of access permissions
The server is attempting to connect to agent to send configuration data, but the server's IP is not on the list of allowed servers. Make sure the server is allowed in the agent's configuration file.
ERROR: Cannot connect to the trapper port of zabbix server daemon, but it should be available to run the script. Not supported by Zabbix Agent
This error may occur when a remote command is executed on an agent, but it does not return anything. Make sure you are returning some default value.
Cannot find host interface on "host" for item key "jmx["java.lang:type=ClassLoading",LoadedClassCount]". [CHost.update -> CHost.massUpdate -> CHost.massAdd -> CHostGeneral.massAdd -> CHostGeneral.link -> CItem.syncTemplates -> CItem.inherit -> CItemGeneral.prepareInheritedItems]"
You may be trying to apply a template before you defined the host's JMX interface. Add a JMX interface to the host before you apply a template with JMX items.
Unable to select configurations
The configuration could not be retrieved from the database. Check the server log and database table 'config'. The oracle sql scripts to do not have a commit statement, so that may be needed.
ociplogon(): ORA-12516: TNS:listener could not find available handler with matching protocol stack [include/db.inc.php:126]
Zabbix may be creating too many sessions or processes in the Oracle database. Once the limit is reached, you may be seeing this error. Also investigate tuning php.ini file. Look at changing