High availability
High Availability (HA) keeps Litmus Edge running when a device goes down or is taken offline. It works by pairing a primary (active) node with a backup (standby) node that stays in sync and takes over automatically if the primary fails.
Note: High Availability is currently available as a beta feature.
Note: High Availability management requires Litmus Edge Manager (LEM) 2.34.0 or later and Litmus Edge 4.0.5 or later on both devices in the pair.
How LEM monitors high availability pairs
Litmus Edge Manager (LEM) polls each HA pair periodically to retrieve the current status and role of each node. When LEM detects a failover, it automatically updates device roles in the UI. You do not need to manually update roles after a promotion.
LEM reports three pair status values:
- Healthy: Both nodes are reachable and the pair is operating normally
- Degraded: One node is unreachable or the pair is not fully synchronized
- Unknown: LEM cannot determine pair status, typically because polling has not completed or a node is offline
Heartbeat monitoring
HA performs heartbeat checks at 2-second intervals. Failover is triggered after three consecutive missed heartbeats. The following fields display on the primary node:
Field | Description |
|---|---|
Last Sent | Last heartbeat sent to the backup node |
Last Received | Last heartbeat received from the backup node |
Consecutive Failures | Number of consecutive missed heartbeats |
Peer Reachable | Whether the backup is reachable from the primary |
Interval | Frequency of heartbeat signals in seconds |
Failure Threshold | Number of missed heartbeats that triggers failover |
Configuring high availability: LEM vs. Litmus Edge
HA pairs can be configured two ways. Both require a primary and a backup device.
- From LEM: Configure the pair centrally without logging into each device. Recommended when both devices are already connected to LEM and you want to manage HA from a single interface.
- From each Litmus Edge instance directly: Log into each device and configure the pair at the device level. Useful when devices are not yet connected to LEM or are in an air-gapped environment. See High Availability (Litmus Edge) in the Litmus Edge documentation.
Configure a high availability pair
This section provides an overview of HA configuration. For full step-by-step instructions, see Setup a High Availability edge device pairing.
To configure an HA pair:
- In LEM, navigate to Edge Devices, click a device ID, and select the High Availability tab.
- Toggle Enable High Availability on.
- In the Configure High Availability dialog, select a role, select a peer device, confirm IP addresses, and review the configuration.
- Click Create Configuration.
- Click Enable.
High Availability becomes enabled between the primary and backup nodes.