Hello Lukas, On Mon, Oct 15, 2018 at 6:14 PM Lukas Tribus <[email protected]> wrote:
> Hello Sébastien, > > > On Mon, 15 Oct 2018 at 16:40, Sébastien Kurtzemann <[email protected]> wrote: > >> No. Only *restart* closes existing front and backend connections. > >> Reload (both seamless and regular) closes them gracefully, so no > >> request is lost. > > > > > > Okay. I think I confound connections and servers sessions... :( > > Are sessions purged after a seamless reload ? > > > > So is there a way to keep sessions states or to configure haproxy TCP > backends to not send a request to a server that is currently handling a > connection ? > > When haproxy reloads, and your backend server is configured with > maxconn 1 on haproxy: > - the old process will keep 1 connection open to your server, until > all old requests are served (so connections close and the process > exits) > - the new process will open the 1 connection when the first request comes > in > > So there is a moment when both old and new process are running, where > there are actually 2 connections to your backend server (one from the > old haproxy process, one from the new process). > If you don't want that, you cannot reload, you must restart instead. > This will kill the existing session immediately, only allowing for the > new connection. > > There is no way to keep the same TCP session alive across haproxy > reloads or restarts. The old connection must go away and a new > connection must be opened. When you restart, this happens > sequentially, when you reload it's the opposite. > > > Seamless reload makes it possible for haproxy to pass *LISTENING* (but > not established) sockets from the old to the new process, so that we > don't loose any new incoming connections on the frontend while > reloading. Existing connections and transaction however are still > handled by the old process, until it can close them. > > > > Lukas > Thanks for your explanations : it's clearer for me ! Our goal is to - have some initial "free" servers in a tcp backend (for example 5 pods) - when a connection start : one and only one "free" server handle it and it become "busy" (we do this with maxconn=1) - add a new "free" servers in the backend, to keep the initial number of "free" servers The problem we have with seamless reload: in some case a "busy" server would received a new connection because after reload current session would be 0. And if a do a restart I will lose the "busy" server connection. I need to find another to do this... Perhaps with usage of HAProxy runtime API instead of "seamless reload" as explain in https://www.haproxy.com/blog/dynamic-scaling-for-microservices -with-runtime-api/ ? Thanks, Sébastien
