Backend down check when backend isn't down

Hi community,

I’m starting to get at least once a day this errors…

[WARNING] 131/213634 (7) : Server mediawiki_be_https/mediawiki is DOWN, reason: Layer7 timeout, check duration: 10002ms. 0 active and 0 backup servers left. 0 sessions active, 0 requeued, 0 remaining in queue.
[ALERT] 131/213634 (7) : backend ‘mediawiki_be_https’ has no server available!
[WARNING] 131/213744 (7) : Server mediawiki_be_https/mediawiki is UP, reason: Layer7 check passed, code: 200, check duration: 229ms. 1 active and 0 backup servers online. 0 sessions requeued, 0 total in queue.
[WARNING] 131/213851 (7) : Server mediawiki_be_https/mediawiki is DOWN, reason: Layer7 timeout, check duration: 10001ms. 0 active and 0 backup servers left. 0 sessions active, 0 requeued, 0 remaining in queue.
[ALERT] 131/213851 (7) : backend ‘mediawiki_be_https’ has no server available!
[WARNING] 131/213956 (7) : Server mediawiki_be_https/mediawiki is UP, reason: Layer7 check passed, code: 200, check duration: 5850ms. 1 active and 0 backup servers online. 0 sessions requeued, 0 total in queue.
[WARNING] 131/214107 (7) : Server mediawiki_be_https/mediawiki is DOWN, reason: Layer7 timeout, check duration: 10001ms. 0 active and 0 backup servers left. 0 sessions active, 0 requeued, 0 remaining in queue.
[ALERT] 131/214107 (7) : backend ‘mediawiki_be_https’ has no server available!
[WARNING] 131/214253 (7) : Server mediawiki_be_https/mediawiki is UP, reason: Layer7 check passed, code: 200, check duration: 6014ms. 1 active and 0 backup servers online. 0 sessions requeued, 0 total in queue.

i check if was a snapshot from veeam in that time to get timeout when vm is freezing but not coincidence to hour from backup so… is weird.

haproxy is a container using: haproxy:2.3.0-alpine
and mediawiki is another container in the same docker engine: bitnami/mediawiki:latest

my section backend for this is the follow:

global
log stdout format raw local0
daemon
quiet
tune.ssl.default-dh-param 2048
ssl-default-bind-options no-sslv3 no-tls-tickets
ssl-default-bind-ciphers ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES256-SHA:ECDHE-ECDSA-DES-CBC3-SHA:DES-CBC3-SHA:!DSS
ssl-default-server-options no-sslv3 no-tls-tickets

defaults main

never fail on address resolution

default-server init-addr libc,none resolvers docker_resolver resolve-prefer ipv4
mode http
log global
option httplog
##option dontlognull
option http-server-close
option forwardfor except 127.0.0.0/8
option redispatch
option contstats
retries 3
timeout queue 1m
timeout http-keep-alive 10s
timeout check 10s
timeout connect 10s
timeout client 5m
timeout server 5m
maxconn 10000
resolvers docker_resolver
nameserver dns 127.0.0.11:53

backend mediawiki_be_https
mode http
balance roundrobin
option forwardfor
option httpchk HEAD / HTTP/1.1\r\nHost:\ localhost

email: set and send alerts

email-alert mailers mailer
email-alert from “$DOCKER_ENGINE_NAME”."$THIS_CONTAINER_NAME"@domain.tld
email-alert to alerts.haproxy@domain.tld
email-alert myhostname smtp1
email-alert level info
cookie SERVERID insert indirect nocache httponly secure
server mediawiki mediawiki:8080 check inter 5s weight 50 id 1 cookie mediawiki_

and on docker can see both up running for many days.

docker ps -a

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
e8986ee5dcd4 bitnami/mediawiki:latest “/opt/bitnami/script…” 6 days ago Up 6 days 8080/tcp, 8443/tcp mediawiki
f99a393d3b24 haproxy:2.3.0-alpine “/docker-entrypoint.…” 4 weeks ago Up 4 weeks 0.0.0.0:443->8443/tcp, 0.0.0.0:80->8080/tcp, haproxy

messages on mail:
Server mediawiki_be_https/mediawiki is DOWN, reason: Layer7 timeout, check duration: 10001ms. 0 active and 0 backup servers left. 0 sessions active, 0 requeued, 0 remaining in queue

and then after 2 min
Server mediawiki_be_https/mediawiki is UP, reason: Layer7 check passed, code: 200, check duration: 6014ms. 1 active and 0 backup servers online. 0 sessions requeued, 0 total in queue

thanks in advance