How to be sticky on REST lifecycle in haproxy - haproxy

Question

I want to route all requests for a given resource to the same server. If a resource is created on a server, all following requests should be routed to the same server.
To be sticky on the url is not the problem, but how can I fill the stick-table from the first response?
Example:
Request:
POST /resources
{
"value": "bla"
}
Response:
{
"id": "1234",
"value": "bla"
}
GET /resources/1234
{
"id": "1234",
"value": "bla"
}
The second request should be routed to the same server, that handled the first request. Is there a way to get this done with haproxy?

Answer 1

Finally found a solution that works. I am posting this, in case somebody else is interested in the solution. The relevant lines are the following in section backend:
acl recources_path capture.req.uri,field(1,?) /resources
stick-table type string len 10 size 5M
stick match capture.req.uri,field(3,/)
# trying to parse the id out of the post response
stick store-response res.payload(0,0),field(2,{),field(4,\") if METH_POST recources_path
Especially the parsing of the response body seems to be not the intended way to use haproxy. Adding a response header with the resource id makes it much easier to handle the situation.