haproxy stopped balancing after about 2 weeks

[ericr]

A couple of weeks ago I installed haproxy on our server running FreeBSD
11.0-RELEASE-p16. (yes, I know it's an old version of the OS, I'm going to
upgrade it as soon as I solve my haproxy problem.)

Haproxy is supposed to load balance between 2 web servers running apache.
haproxy ran fine and balanced well for about 2 weeks, and then it stopped
sending client connections to the second web server.

It still does health checks to both servers just fine, and reports L7OK/200
at every check for both servers. I've tried using both roundrobin and
leastconn, with no luck.  I've restarted haproxy several times, and
rebooted the server it's running on, and it the behavior doesn't change.
I'm out of ideas, does anyone have suggestions for fixing this (or
improving my config in general)?

Here's my config file:

<code>
# global holds defaults, global variables, etc.
global
        daemon
        user haproxy
        group haproxy
        log /dev/log local0
        stats socket /var/run/haproxy/admin.sock user haproxy group haproxy
mode 660 level admin

        # https://www.haproxy.com/blog/multithreading-in-haproxy/
        maxconn 2048 # max connections we handle at once
        nbproc 1 # number of haproxy processes to start
        nbthread 4 # max threads, 1 per CPU core

        # cpu map = number of cpu cores
        cpu-map all 0-3

        ssl-default-bind-ciphers "EECDH+ECDSA+AESGCM ECDH+aRSA+AESGCM
EECDH+ECDSA+SHA384 EECDH+ECDSA+SHA256 EECDH+aRSA+SHA384 EECDH+aRSA+SHA256
EECDH+aRSA+RC4 EECDH EDH+aRSA RC4"
        ssl-default-bind-options ssl-min-ver TLSv1.2

defaults
        timeout connect 30s
        timeout client 600s
        timeout server 30s
        log global
        mode http

        stats enable
        stats uri /haproxy?stats
        stats realm Statistics
        stats auth REMOVED
        stats refresh 10s

# frontend holds info about the public face of the site
frontend vi-gate2.docbasedirect.com
        bind XXX.XX.XX.XXX:80
        bind XXX.XX.XX.XXX:443 ssl crt
"/usr/local/etc/2019-www-prod-SSL.crt"
        http-request redirect scheme https if !{ ssl_fc }
        default_backend web_servers
        option httplog

# info about backend servers
backend web_servers
        balance leastconn
        cookie phpsessid insert indirect nocache
        option httpchk HEAD /

        default-server check maxconn 2048

        server vi-www3 10.3.3.10:8080 cookie phpsessid inter 120s
        server vi-www4 10.3.3.11:8080 cookie phpsessid inter 120s

        email-alert mailers vi-mailer
        email-alert from REMOVED
        email-alert to REMOVED

mailers vi-mailer
        mailer localhost 127.0.0.1:25
        mailer vi-backup2 10.3.3.100:25
</code>

Thanks!

-- ericr