Routing

Manual overrides

Since an automatically generated routing table can only be changed with a service deployment additional routing commands can be stored manually in the consul KV store which get appended to the automatically generated routing table. This allows fine-tuning and fixing of problems without a deployment.

The routing commands are also stored in the KV store.

Config Language

The routing table is configured with the following commands:

route add <svc> <src> <dst> weight <w> tags "<t1>,<t2>,..."
  - Add route for service svc from src to dst and assign weight and tags

route add <svc> <src> <dst> weight <w>
  - Add route for service svc from src to dst and assign weight

route add <svc> <src> <dst> tags "<t1>,<t2>,..."
  - Add route for service svc from src to dst and assign tags

route add <svc> <src> <dst>
  - Add route for service svc from src to dst

route del <svc> <src> <dst>
  - Remove route matching svc, src and dst

route del <svc> <src>
  - Remove all routes of services matching svc and src

route del <svc>
  - Remove all routes of service matching svc

route weight <svc> <src> weight <w> tags "<t1>,<t2>,..."
  - Route w% of traffic to all services matching svc, src and tags

route weight <src> weight <w> tags "<t1>,<t2>,..."
  - Route w% of traffic to all services matching src and tags

route weight <svc> <src> weight <w>
  - Route w% of traffic to all services matching svc and src

route weight service host/path weight w tags "tag1,tag2"
  - Route w% of traffic to all services matching service, host/path and tags

    w is a float > 0 describing a percentage, e.g. 0.5 == 50%
    w <= 0: means no fixed weighting. Traffic is evenly distributed
    w > 0: route will receive n% of traffic. If sum(w) > 1 then w is normalized.
    sum(w) >= 1: only matching services will receive traffic

    Note that the total sum of traffic sent to all matching routes is w%.

The order of commands matters but routes are always ordered from most to least specific by prefix length.

Routing rules

The routing table contains first all routes with a host sorted by prefix length in descending order and then all routes without a host again sorted by prefix length in descending order.

For each incoming request the routing table is searched top to bottom for a matching route. A route matches if either host/path or - if there was no match - just /path matches.

The matching route determines the target URL depending on the configured strategy. rnd and rr are available with rnd being the default.

Example

The auto-generated routing table is

route add service-a www.mp.dev/accounts/ http://host-a:11050/ tags "a,b"
route add service-a www.kjca.dev/accounts/ http://host-a:11050/ tags "a,b"
route add service-a www.dba.dev/accounts/ http://host-a:11050/ tags "a,b"
route add service-b www.mp.dev/auth/ http://host-b:11080/ tags "a,b"
route add service-b www.kjca.dev/auth/ http://host-b:11080/ tags "a,b"
route add service-b www.dba.dev/auth/ http://host-b:11080/ tags "a,b"

The manual configuration under /fabio/config is

route del service-b www.dba.dev/auth/
route add service-c www.somedomain.com/ http://host-z:12345/

The complete routing table then is

route add service-a www.mp.dev/accounts/ http://host-a:11050/ tags "a,b"
route add service-a www.kjca.dev/accounts/ http://host-a:11050/ tags "a,b"
route add service-a www.dba.dev/accounts/ http://host-a:11050/ tags "a,b"
route add service-b www.mp.dev/auth/ http://host-b:11080/ tags "a,b"
route add service-b www.kjca.dev/auth/ http://host-b:11080/ tags "a,b"
route add service-c www.somedomain.com/ http://host-z:12345/ tags "a,b"