Load balancing by cookie

[samutamm]

Sometimes we might want the same instance to serve all request from a user, during the whole session. This way all user or session specific data is loaded and cached to only one instance.

The reverse Proxy currently supports load balancing using roundRobin, random, weightedRandom, ipHash or headerHash strategies. ipHash and headerHash enables routing clients to specific instances using ip or a header field as hashing key. It would be nice if one could use cookie also to choose the instance, eg. cookieHash load balancing strategy.

While this can already be achieved by using headerHash and specifying Cookie/Set-Cookie header,

loadBalance:
  policy: headerHash
  headerHashKey: Set-Cookie

it would be more convenient to only specify

loadBalance:
  policy: cookieHash

Then later in the future, to go even further with cookieHash, the cookie could be generated and added to response, when user sends the first request.