Load-balanced Sentinet Nodes

In a typical production environment, Sentinet Nodes are expected to be load-balanced (or clustered) to avoid using a Sentinet Node as a single point of failure. To deploy a cluster of Sentinet Nodes, administrators register a single logical Node in the Repository and then install and configure multiple physical Node instances within different IIS Server machines. Each physical Sentinet Node must be deployed and configured with the same configuration options to avoid ambiguity during runtime. This means that all Node instances must be deployed with the same X.509 certificate, run under the same IIS Application pool identity, are enabled with the same transports and security capabilities, and have the same base address and port assignments (which will be an external load-balancer address and port). When each physical instance is configured using the Node Configuration Wizard, administrators select the same single logical Node instance in the Repository tree, which effectively allows all physical Node instances to acquire the same exact configuration and execute identically under load-balanced scenarios (see Node Instance Identity chapter for more details on load-balanced Node instances).

Sentinet Nodes provide monitoring data with the client IP addresses acquired from the immediate sender of the messages. In the case when Sentinet Nodes are deployed behind the network load-balancers, immediate sender is the load-balancer, not the actual client application. To handle the client IP address misrepresentations in these deployment scenarios, Sentinet supports client IP address acquisition from the sender's designated HTTP header. Most industry standard load-balancers support designated HTTP header that they create with the value of the original client IP address. The header is sent to the message recipient so that the recipient can retrieve the original client IP address from the header value; most often this header is X-Forwarded-For. To configure the Sentinet Node with this special HTTP header, expand Advanced Sentinet Node properties and enter the name of HTTP header that the load-balancer designated for the original client IP address forwarding.

Figure. HTTP header name that is assigned to retrieve original client IP addresses from.

Use Last or First IP address setting to define which IP address to use from the list of addresses, if the HTTP header contains a list of IP addresses. Default setting is Last IP address.