Elastic Network Interface

The Elastic Network Interface separates the network interface from an EC2 instance so you can attach and detach the instance from MarkLogic nodes. The ENI is assigned a private IPv4 address, so that attaching and detaching the ENI will not affect the assigned IPv4 address. This alleviates the burden to manage the hostname change when instances fail.

AWS enforces a default limitation of ENIs per Region. However, AWS can increase the limit upon request. For details about the default limitation of ENIs per Region, see Amazon VPC quotas.

The MarkLogic CloudFormation templates creates ENIs based on the total nodes in the cluster (by Managed ENI stack). When a node is launched in a group, the Node Manager will attach ENIs to the new node.

Note that the ENI created and attached to instances will be the secondary network interface of the instance. The Managed Cluster locates the secondary network interface and uses its private DNS name or private IP address as the hostname for the new MarkLogic node. Because the ENI's private DNS name and IP address are static, the hostname for a MarkLogic node is also static, even if an instance fails and a new instance kicks in to assume the role in the cluster.

If you chose to set up the cluster manually or with your own templates, it is recommended that you create ENIs. Otherwise your private IPv4 address will be released when the node is terminated.