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  1. Undertow
  2. UNDERTOW-898

Failover targets should be chosen deterministically

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    Description

      Undertow task

      We would like to have this bit of configurable logic, off by default, implemented in Undertow. The C implementation is clear enough, the algorithm is just one line. I believe it could be translated to Undertow mod_cluster Proxy logic.

      See: https://github.com/modcluster/mod_proxy_cluster/pull/8/files

      Description

      Under the following conditions:
      1. A request arrives for a session with an unknown route
      2. A request arrives for a session with a known route in an error state, or if the intended worker is unresponsive and needs to failover

      ... the failover target must be chosen in a deterministic way. This is meant to mitigate the situation where concurrent requests failover to different nodes and cause cluster-wide contention for the session. Given a consistent ordering of workers (e.g. lexographically), the failover target should be chosen by something like: hash code of session id % active worker count.

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              rhn-engineering-rhusar Radoslav Husar
              mbabacek1@redhat.com Michal Karm
              Michal Karm Michal Karm
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