frontend fe_http
    bind :80
    acl canary_header req.hdr(X-Canary) -i 1 true yes
    use_backend be_canary if canary_header
    default_backend be_stable

backend be_stable
    server stable1 10.0.10.11:8080 check

backend be_canary
    server canary1 10.0.10.21:8080 check