OlegShepelev Member since 2014 11 posts
Posted: 3 years ago
Last activity: 3 years 7 months ago

Hot and Cold Failover

What's a hot failover in terms of Pega PRPC?

In CLSA course book it's written like this:

In a cold failover, load balancing systems send a heartbeat to the nodes to check if they are still running. This heartbeat can be configured in the application server and can be sent each minute, or once every two minutes or so. When the server is down, it sends a notification to the load balancer and moves the sessions to another server. The session information that is not stored or committed to database is lost.

In case of high available applications, we can enable failover by changing the passivation setting to use shared storage (Changing storage/class/passivation: /rootpath). This setting is usually set using the dynamic system settings. When configured, the requestors accessing a JVM are redirected to another JVM through the load balancer when the server crashes. The user must authenticate again to establish their session in the new node. All information that is not committed is lost in the process.

Thus, a cold failover is a situation when one of the servers is down and its sessions are moved to the other one. Servers are being controlled by application server sending heartbeats, ok. But what's a hot failover in this case? I've failed to find any information concerning this neither in course book nor in High Availability Documentation, nor in PDN.

***Updated by moderator: Lochan to move post from PSC to Pega Academy***

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