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Concepts and Terminologies

Node Roles

A HyWorks node in a cluster can have the following roles:

Primary HyWorks Management Role: This is the primary management node that takes care of the management of HyWorks functions as well as the infrastructure.

Secondary HyWorks Management Role: This is the backup management node that becomes active only when the Primary HyWorks Management Node is unavailable or in fault or maintenance mode.

HyWorks Session Role: These are one or more nodes that handles user login, session launch, session time management, logout and other user session related aspects.
These are the nodes to which the user endpoints are connected.
When more than one node is available, an external load balancer is used to to distribute the load across these nodes. These nodes are stateless and a simple L3 or L4 based balancing can be used.

Database Role: In a HyWorks cluster, at least one database node is required. The Microsoft SQL server express edition is the minimum version that is needed.
HyWorks has built-in synchronization between the two nodes of the databases. External database clustering is not mandatory.
If an existing, shared database is to be used, the HyWorks database clustering does not need to be enabled.
In a HyWorks cluster, HyWorks Management, Session and database roles can work on the same node.

Node States

HyWorks Controller Modes: The HyWorks Controller, when configured in a cluster, can exist in the following states:

  • Active: The node that actively serves user/management connections. The HyWorks Management node as well as the HyWorks Session Node can exist in an Active state.

  • Secondary: This node acts as a backup server and will not service any end user connection or management functions.

  • Fault Mode: The HyWorks Controller mode where it cannot function correctly, but the HyWorks Controller Service is still running, for example when the database services are down, or license services are down.

  • Maintenance Mode: The HyWorks Controller mode in which it does not interact with another server in the cluster. Maintenance mode can be used to conduct management activities on the Controller to avoid any synchronization, which could lead to data corruption.

HyWorks Controller Failover Cases

In this section, failover cases will be listed, on occurrence of which HyWorks Controller switching will happen and healthy and reachable server will take over the role of "Primary" management node:

Primary Server goes down

If primary HyWorks controller node goes down, secondary will take over as primary and on resolving primary server controller it will take the role of secondary management server.

License issues on primary HyWorks controller

On experiencing following licensing error condition, primary HyWorks controller will go into fault mode and secondary HyWorks controller will take control and become primary:

  • License key on primary server is corrupted
  • License on primary server is expired
  • HyWorks controller is not able to communicate with licensing service (Licensing service is down)

Communication failure with database server

If primary HyWorks controller fails to connect with it's database server, primary HyWorks controller will move to fault mode and secondary HyWorks controller will take control and become primary.

Important

  • On experiencing SQL transaction errors or intermediate timeouts, HyWorks controller does not move into fault state and may retain its primary role.

HyWorks controller service goes down

In case, when HyWorks controller goes down on primary management node, secondary server will take the new primary role. On start of HyWorks controller service, old primary server will take role of secondary.

Network Un-reachability

If primary HyWorks controller faces any network issues and secondary node is unable to connect, then secondary server will become primary.

Note

  • Primary HyWorks controller will retain it's primary role, as it will also have communication failure with secondary node
    • HyWorks client will be able to connect to any of the reachable HyWorks controller nodes as both will be maintaining primary role.
  • On restoring network communication between two nodes, any node can remain primary and it will depend on condition: which server is going to poll the status of other server

Manual Switching

Other than conditions mentioned above, administrator can also force controller switching:

  • On moving primary HyWorks controller into maintenance mode, secondary controller will automatically take role of primary
  • Moving primary to secondary and secondary to primary manually from HyWorks Controller Management Console -> Server -> HyWorks Controller section