1. High availability for end-users

Using load balancer can achieve this requirement. One active application server will handling processing the jobs and multiple passive application servers with behind a load balancer will handle serving the data to end users and integration applications. If one of the passive app server application servers dies, the load balance balancer is responsible for distributing the request to a working passive server to answer the request.

In a clustered Semarchy xDM environment there will be 1 instance of semarchy.war and N instances of semarchy-passive.war deployed. The one instance of semarchy.war is the active instance.

See this documentation for more information on the Reference Architecture for High-Availability:

https://www.semarchy.com/doc/semarchy-xdm/semng.html#high-availability-configuration

2. High availability for processing batches 

(Incomplete article, requires more investigation and better solution!)

Unfortunately, the The HTTP load balancer can only address the requirement front-end for users and applications. We do not have Semarchy xDM does not include a built-in solution configuration to address high availability for xDM managing and running the certification processes's scheduler component.

The Semarchy customer should use a monitoring solution that checks for the health of the one active server and takes action if the active server is down so it doesn't need an administrator to manually restart xDM/tomcatthe xDM application or application server.

This monitoring solution can exist in multiple forms from a DIY application to enterprise-grade software application.

Enterprise Monitoring Software

Some corporate customers use an internal monitoring service, such as New Relic, AppDynamics, Ruxit and others.

AWS world

Customers can build a DIY solution with a combination of auto-scaling groups, Cloudwatch custom metrics, and homegrown scripts and alarms.

For example, VIP uses a fairly manual process to monitor the status check from AWS. Since they are behind an ELB, they can take advantage of some application health checks. 

Other solutions that we haven't tried include: Mmonit.com/monit and Nagios.