Citrix ADM Service agent behavior for Pooled Licensing

The Citrix ADM agent works as an intermediary between Citrix ADM and the discovered instances across different data centers and public clouds. ADM Service requires a minimum of one agent per tenant for pooled licensing to work. Multiple ADM Service agents can be deployed per site or multi-site for redundant management purposes, but only one agent can have the License Server Agent (LSA) licensing role for the entire tenant deployment.

Multiple Citrix ADM agents behavior

In a deployment with a combination of multiple agents and multiple sites, the ADM agents follow the client/server architecture.

The first/oldest ADM Service agent registered in an UP state is assigned the LSA role. Any other agents added later act as a client/proxy and communicate with the agent hosting the main LSA role for license allocation. Each Citrix ADM agent hosting the proxy role communicates to the agent with the current LSA role through the Citrix ADM cloud plane.

Note

There is no direct communication between ADM agents and the ADM Service agent hosting the LSA role, and all the connections go through ADM Service only.

ADM Service agent Failover behavior

The ADC Pooled Agent failover works in a multi-agent deployment in the following way.

Assume that there are two ADM Service agents - AG1, and AG2. Now,

• AG1 is configured to use ADC11, ADC12, ADC13 as the remote license host or LSA

• AG2 is configured to use ADC21, ADC22, ADC23 as the remote license host or LSA

• AG2 is acting as the License Server

  • If AG1 fails, ADC11, ADC12, and ADC13 automatically connect through AG2 for license reconciliation.
    • ADC11, ADC12, and ADC13 might still notice a small period of Grace, if a few heartbeats are missed, while this reconnection happens.
  • If AG2 fails, all ADCs continue to stay in Grace until:
    • Either AG2 comes back up/is brought backup
    • Or AG2 is deleted from ADM Service. Once deregistered, ADM service designates AG1 as the ADM Agent with the LSA role.
    • After the election has completed, AG1 starts allocating and reconciling resources to the configured instances.

  Note

  The LSA agent must not be down for longer than the grace period. If this agent is not recoverable, it must be deleted from ADM Service which deregisters the LSA role from the agent and an election is held to determine a new ADM Service agent to host the LSA role.

For questions related to LSA, see FAQs on License Server Agent
.