NXLog Agent failover

NXLog Agent includes built-in active/passive failover functionality that offers a straightforward method for maintaining high availability. For more complex scenarios, it can also work with third-party failover solutions.

Types of failover

There are several failover node configuration models. However, the two most common models are active/passive and active/active:

Active/passive: One node in the cluster is the active node, while the other nodes are in standby. If the initial active node fails, the cluster elects one of the standby nodes to become the active node.
Active/active: All nodes in the cluster are active, effectively performing load balancing. If one of the nodes fails, the cluster directs traffic to one or more of the remaining nodes. This failover model ensures that there are no idle nodes, and depending on the number of nodes, has the advantage of increasing performance.

Additionally, some applications, like NXLog Agent, implement failover mechanisms (self-managed failover), while specialized software like HAProxy provides external load balancing and failover (externally managed failover):

Self-managed failover: Also known as same-tier failover, self-managed failover occurs entirely within the application without needing additional external hosts. Each node in the cluster contains a failover configuration.
Externally managed failover: Nodes in an externally managed failover cluster are unaware of their peers and do not contain any configuration that defines them as part of a cluster. It relies entirely on an external host to determine the active nodes and the viable peers. See Emulating Active/Passive Application Clustering with HAProxy for an example.

Understanding the differences between self-managed and externally managed failover is paramount in selecting the right approach. NXLog Agent includes built-in support for self-managed and externally managed failover, offering flexibility for different use cases.

See also Configure load balancing for configuration examples.

Failover-enabled NXLog Agent modules

All network-based NXLog Agent modules support failover:

NXLog Transport (im_batchcompress, om_batchcompress)
DBI (im_dbi)
Elasticsearch (om_elasticsearch)
HTTP(s) (im_http, om_http)
Microsoft Azure(im_azure, om_azure)
Raijin (om_raijin)
Redis (im_redis)
Remote Management (xm_admin)
TCP (im_tcp, om_tcp)
TLS/SSL (im_ssl, om_ssl)
UDP (im_udp, om_udp, om_udpspoof)