Table of Contents

1 Alta disponibilità

1 Alta disponibilità

Overview

The high availability mode offers protection against software/hardware failures for Zabbix server and allows to minimize downtime during software/hardware maintenance.

The high availability (HA) cluster is an opt-in solution and it is supported for Zabbix server. The native HA solution is designed to be simple in use, it will work across sites and does not have specific requirements for the databases that Zabbix recognizes. Users are free to use the native Zabbix HA solution, or a third party HA solution, depending on what best suits the high availability requirements in their environment.

The solution consists of multiple zabbix_server instances or nodes. Every node:

is configured separately (configuration file, scripts, encryption, data export)
uses the same database
has several modes: active, standby, unavailable, stopped

Only one node can be active (working) at a time. The standby nodes do no data collection, processing or other regular server activities; they do not listen on ports; they have minimum database connections.

Both active and standby nodes update their last access time every 5 seconds. Each standby node monitors the last access time of the active node. If the last access time of the active node is over 'failover delay' seconds, the standby node switches itself to be the active node and assigns 'unavailable' status to the previously active node.

The active node monitors its own database connectivity - if it is lost for more than failover delay-5 seconds, it must stop all processing and switch to standby mode. The active node also monitors the status of the standby nodes - if the last access time of a standby node is over 'failover delay' seconds, the standby node is assigned the 'unavailable' status.

The failover delay is configurable, with the minimum being 10 seconds.

The nodes are designed to be compatible across minor Zabbix versions.

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Server configuration

To turn any Zabbix server from a standalone server into an HA cluster node, specify the HANodeName parameter in the server configuration.

The NodeAddress parameter (address:port), if set, must be used by the frontend for the active node, overriding the value in zabbix.conf.php.

Preparing frontend

Make sure that Zabbix server address:port is not defined in the frontend configuration.

Zabbix frontend will autodetect the active node by reading settings from the nodes table in Zabbix database. Node address of the active node will be used as the Zabbix server address.

Proxy configuration

To enable connections to multiple servers in a high availability setup, list addresses of the HA nodes in the Server parameter of the proxy, separated by a semicolon.

Agent configuration

To enable connections to multiple servers in a high availability setup, list addresses of the HA nodes in the ServerActive parameter of the agent, separated by a semicolon.

Failover to standby node

Zabbix will fail over to another node automatically if the active node stops. There must be at least one node in standby status for the failover to happen.

How fast will the failover be? All nodes update their last access time (and status, if it is changed) every 5 seconds. So:

If the active node shuts down and manages to report its status as "shut down", another node will take over within 5 seconds.
If the active node shuts down/becomes unavailable without being able to update its status, standby nodes will wait for the failover delay + 5 seconds to take over

The failover delay is configurable, with the supported range between 10 seconds and 15 minutes (one minute by default). To change the failover delay, you may run:

zabbix_server -R ha_set_failover_delay=5m

Managing HA cluster

The current status of the HA cluster can be managed using the dedicated runtime control options:

ha_status - log HA cluster status in the Zabbix server log;
ha_remove_node=target - remove an HA node identified by its <target> - number of the node in the list (the number can be obtained from the output of running ha_status). Note that active/standby nodes cannot be removed.
ha_set_failover_delay=delay - set HA failover delay (time suffixes are supported, e.g. 10s, 1m)

Node status can be monitored:

in Reports → System information
in the System information dashboard widget
using the ha_status runtime control option of the server (see above).

The zabbix[cluster,discovery,nodes] internal item can be used for node discovery, as it returns a JSON with high availability node information.

Disabling HA cluster

To disable a high availability cluster:

make backup copies of configuration files
stop standby nodes
remove the HANodeName parameter from the active primary server
restart the primary server (it will start in standalone mode)

Upgrading HA cluster

To perform a major version upgrade for the HA nodes:

stop all nodes;
create a full database backup;
if the database uses replication make sure that all nodes are in sync and have no issues. Do not upgrade if replication is broken.
select a single node that will perform database upgrade, change its configuration to standalone mode by commenting out HANodeName and upgrade it;
make sure that database upgrade is fully completed (System information should display that Zabbix server is running);
restart the node in HA mode;
upgrade and start the rest of nodes (it is not required to change them to standalone mode as the database is already upgraded at this point).

In a minor version upgrade it is sufficient to upgrade the first node, make sure it has upgraded and running, and then start upgrade on the next node.

Implementation details