The azure-events Resource Agent Does Not Failover Properly When Cluster Nodes Are Distributed Across Availability Zones

This document (000020578) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Server for SAP Applications 12
SUSE Linux Enterprise High Availability Extension 15
SUSE Linux Enterprise High Availability Extension 12

Situation

The azure-events resource agent allows Azure-hosted High Availability clusters to query the Azure Instance Metadata Service (IMDS) to determine if maintenance events are scheduled for cluster nodes.  If an event is observed, the impacted node is placed in Standby and hosted resources are migrated to other nodes in the cluster. More information on this topic can be found in the following blog:

https://www.suse.com/c/the-azure-events-resource-agent-pacemaker-clusters-and-you/
 

Resolution

The Microsoft Azure Platform team is currently researching a fix to this limitation.  However, we currently recommend that High Availability clusters be located within the same Availability Zone, if the azure-events resource agent is to be utilized.
 

Cause

Network routing for the IMDS API uses a link-local address (169.254.169.254) that is not routable between availability zones.  Therefore, nodes can only observe events for nodes within the Availability Zone where they are hosted.  The azure-events monitor requires that each node in the cluster is able to observe events for all other cluster nodes.  Since this is not possible across availability zones, the azure-events resource agent may not work properly in this scenario.

Additional Information

https://docs.microsoft.com/en-us/azure/virtual-machines/workloads/sap/sap-ha-availability-zones

Disclaimer

This Support Knowledgebase provides a valuable tool for SUSE customers and parties interested in our products and solutions to acquire information, ideas and learn from one another. Materials are provided for informational, personal or non-commercial use within your organization and are presented "AS IS" WITHOUT WARRANTY OF ANY KIND.

  • Document ID:000020578
  • Creation Date: 03-Feb-2022
  • Modified Date:04-Feb-2022
    • SUSE Linux Enterprise High Availability Extension
    • SUSE Linux Enterprise Server for SAP Applications

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