4.6 Module classy_liveness

A process that is tasked with monitoring liveness status of peers. Its responsibilities include:

  1. detecting that remote sites are down, making a coordinated decision that the site is down.
  2. automatically kick sites that have been down from the cluster.

Relevant configurations are max_site_downtime and quorum.

In a partitioned network there is a risk that sites try to kick each other.

Liveness requires quorum of running nodes before making the decision to kick. Note: as quorum(running) is always >= quorum(config), even in a partition containing single node, liveness won’t activate if quorum config is set to a value > 1.

4.6.1 Functions

n_restarts()
-spec n_restarts() -> {ok, non_neg_integer()} |
                      {error, nodedown}.

Return number of node restarts since creation of the site.

This value is monotonically increasing.

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