> Hi, > > I'm experiencing a problem with backend TCP connections being reset > [RST+ACK] by HAProxy after serving one HTTP request and receiving the > [ACK] for the HTTP response. Delay between backend's [ACK] and > haproxy's [RST+ACK] seems random, ranging from single seconds to > several minutes. > > What I wanted to achieve is: for each backend server keep a limited > pool of backend TCP connections open, and when a HTTP request comes in > through the frontend, reuse one of the existing connections (in HTTP > keep-alive mode), creating one if necessary.
What you are describing is connection pooling/multiplexing, but thats not supported (yet). > It was my understanding that 'timeout server 5m' should keep backend > connections opened for 5 minutes before closing them. Was I mistaken? Yes, this is a timeout for the case when the server is supposed to send something, but doesn't [1], *not for a keep-alive use-case*. > Would "timeout tunnel" allow me to specify such timeout, despite > HAProxy working in http-keep-alive mode? No. Here is what you need to know (valid for the 1.5 stable releases): - the frontend and backend connections are 1:1, meaning one frontend connection always has one backend connection. If either of those two connections are closed, the other side needs to close as well. You cannot reuse a backend connection for a request coming from a different/new frontend connection. You cannot have a backend connection pool and reuse them for frontend requests. Its possible that this will come in 1.6. - with "option http-tunnel" [2], which was the default in 1.4 release, the HTTP connection is transformed into a TCP tunnel, so after the first request, HAproxy just forwards TCP between the client and the server. This brings some problems with it. For example, ACL, content switching and all HTTP based feature cannot work for subsequent HTTP request in a TCP session. Keepalive does work if server and client support it. Keepalive timeout is specified by "timeout tunnel". - with "option http-keep-alive" [3], which is the new 1.5 default, HAProxy understands the keep-alive part, and looks and understand every request. The 1:1 mapping is still valid and you still can't do connection "pooling". Keep-alive timeout is specified by "timeout http-keep-alive". "option prefer-last-server" [4] is recommended if you don't have any other client "stickiness" configurations. - "option http-server-close" [5] does keep-alive on the client side only. "timeout http-keep-alive" is used here as well. Hope this helps, Lukas [1] http://cbonte.github.io/haproxy-dconv/configuration-1.5.html#4.2-timeout%20server [2] http://cbonte.github.io/haproxy-dconv/configuration-1.5.html#option%20http-tunnel [3] http://cbonte.github.io/haproxy-dconv/configuration-1.5.html#option%20http-keep-alive [4] http://cbonte.github.io/haproxy-dconv/configuration-1.5.html#option%20prefer-last-server [5] http://cbonte.github.io/haproxy-dconv/configuration-1.5.html#option%20http-server-close
