To prevent unwanted disconnections, it is important to understand the potentially complex interaction between HA settings and the environment in which your cluster runs. Settings that are not appropriate for a particular environment can lead to unwanted disconnections under certain circumstances.

In general, it is advisable to maintain an L1-L2 HealthChecker timeout that falls between the L2-L2 HealthChecker timeout as modified in the following inequality:

This allows a cluster's L1s to avoid disconnecting before a client reconnection window is opened (a backup L2 takes over), or to not disconnect if that window is never opened (the original active L2 is still functional). The Election Time and Client Reconnect Window settings, which are found in the Terracotta configuration file, are respectively 5 seconds and 120 seconds by default.

For example, in a cluster where the L2-L2 HealthChecker triggers at 55 seconds, a backup L2 can take over the cluster after 180 seconds (55 + 5 + 120). If the L1-L2 HealthChecker triggers after a time that is greater than 180 seconds, clients may not attempt to reconnect until the reconnect window is closed and it's too late.

If the L1-L2 HealthChecker triggers after a time that is less than 60 seconds (L2-L2 HealthChecker + Election Time), then the clients may disconnect from the active L2 before its failure is determined. Should the active L2 win the election, the disconnected L1s would then be lost.

A check is performed at server startup to ensure that L1-L2 HealthChecker settings are within the effective range. If not, a warning with a prescription is printed.