fabio builds the routing table from the Consul service registrations, health
check status and the user provided
route commands stored in the Consul KV
store. This is the core feature of fabio - the reason it exists.
The cluster wide state is stored in the Consul Raft log which provides a consistent view of the available and healthy services in the cluster.
When the Raft log changes fabio is notified and downloads the list of healthy services and the user defined routes from the KV store and re-builds the routing table.
Once the new routing table has been built it is atomically swapped with the active routing table without any service interruption. Existing connections remain open and running requests are served even if the new routing table no longer contains that route.
Registering or de-registering a service, setting a node to maintenance mode, failing or passing of a health check for a service, or writing data into the Consul KV store all trigger an automatic reload of the fabio routing table for all fabio nodes in the cluster.
This all happens automatically, with no downtime, or manual intervention.