The HAClient, provided in the AMPS client libraries, provides the following additional capabilities as compared to the Client:
- Automatic reconnection and failover (with a configurable delay strategy)
- Automatic resubscription when reconnecting
- Optional durable publishing (across reconnection and across restarts)
- Optional resumable bookmark subscriptions that start from the last processed message (across reconnection and across restarts)
- Optional heartbeating to actively detect disconnection
While these capabilities are necessary for many applications, there's no requirement that you use the HAClient if you will not be using these capabilities. You do not need to use all of the capabilities of HAClient, and you do not need to use an HAClient to use AMPS replication, transaction logs, historical SOW or bookmark subscriptions.
In many cases, however, applications that require high availability can benefit from using the capabilities in HAClient.