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As per various blogs, HAproxy can be gracefully restarted using the following command:

sudo haproxy -f /etc/haproxy/haproxy.cfg -p /var/run/haproxy.pid -sf $(cat /var/run/haproxy.pid)

TO verify this, I had set up a apache bench script which contiguously sent message to haproxy. Ideally, whenever I restarted my server the script should not have an affect on the apache bunch execiton. But, it seems that whenever Haproxy is restarted apache bench scripts terminate and the connection to load balancer is lost.

Here is the details of my HaProxy configuration file :

global
    nbproc 4
    log 127.0.0.1   local0
    log 127.0.0.1   local1 notice
    #log loghost    local0 info
    maxconn 4096
    #chroot /usr/share/haproxy
    user haproxy
    group haproxy
    daemon
    pidfile /var/run/haproxy.pid
    stats socket /home/ubuntu/haproxy.sock
    #debug
    #quiet

    defaults
    log     global
    mode    http
    option  httplog
    option  dontlognull
    retries 3
    option redispatch
    maxconn 2000
    contimeout      5000
    clitimeout      50000
    srvtimeout      50000

    listen webstats
    bind 0.0.0.0:1000
    stats enable
    mode http
    stats uri /lb?stats
    stats auth anand:aaaaaaaa
    #stats refresh

    listen web-farm 0.0.0.0:80
         mode http
         balance roundrobin
         option httpchk HEAD /index.php HTTP/1.0
         server server2.com  1.1.1.1:80
         server serve1.com  1.1.1.2:80

~
Please let me know what am I missing here.

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migrated from stackoverflow.com Nov 14 '11 at 17:14

This question came from our site for professional and enthusiast programmers.

    
Do you enable keepalive in ab? –  minaev Dec 16 '11 at 9:44

1 Answer 1

While troubleshooting this, try to use "nbproc 1" instead of "nbproc 4", increasing the number of processes is rarely needed, and could potentially lead to issues in certain cases.

However, this is most likely not the main problem. The scenario you describe should actually work as you expect.

HAProxy's hot reconfiguration actually works like this :

  1. A new process is started with the specified configuration
  2. The old process receives a SIGTTOU signal so that the new process can take over the port(s)
  3. The old process finishes it's current work and then exits
  4. The new process handles traffic over the port(s)

If anything goes wrong after 2, the old process instead receives a SIGTTIN signal, and continues as before.

Some additional detail in your question could make troubleshooting this problem easier:

  • What parameters do you use with ab
  • After a hot reconfiguration, can you connect to the new process with any other clients or not
  • Which (major) version of HAProxy are you using
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