Table of Contents
The Heartbeat messaging layer comprises several interlocking but distinct components.
The Heartbeat communication module provides strongly authenticated, locally-ordered multicast messaging over basically any media, IP-based or not. Heartbeat supports cluster communications over the following network link types:
- unicast UDP over IPv4;
- broadcast UDP over IPv4;
- multicast UDP over IPv4;
- serial link communications.
![[Warning]](images/warning.png) | Warning |
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Please consider some important caveats with regard to serial
link connectivity (see the |
Heartbeat can detect node failure reliably in less than a half-second. It will register with the system watchdog timer if configured to do so.
The heartbeat layer has an API which provides the following classes of services:
- intra-cluster communication - sending and receiving packets to cluster nodes
- configuration queries
- connectivity information (who can the current node hear packets from) - both for queries and state change notifications
- basic group membership services