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Reply to topic   Topic: apache2ctl graceful on websockets connections

Joined: 09 Oct 2020
Posts: 1

PostPosted: Fri 09 Oct '20 13:44    Post subject: apache2ctl graceful on websockets connections Reply with quote


I have a reverse proxy with apache 2.4.29-1ubuntu4.14 running on ubuntu 18.04 in front of multiple servers. One of these servers (Rocket.Chat, if it matters) is using websockets, connections that seem to be more persistent than a simple HTTP request from what I see.

My problem comes when I change the apache configuration and I run
apache2ctl graceful

The workers that are currently handling websockets connections remain in an ESTABLISHED state and never reload. This leads to some of the other requests to be handled with the old apache config.

The only way past this I found is to fully restart apache, but I don't want to do that in the middle of the day when people are working. So when I need to change the apache config, I have to wait for out of working hours to do a full apache restart.

Is there a way to gracefully reload the apache config without breaking peoples connections?

This is how the vhost for proxying wss requests looks like:
<VirtualHost *:443>
    ServerName chat.domain.com

    LogLevel info
    ErrorLog /var/log/chat.domain.com_error.log
    TransferLog /var/log/chat.domain.com_access.log

    SSLEngine On
    SSLCertificateFile /etc/ssl/certs/chat.domain.com.crt
    SSLCertificateKeyFile /etc/ssl/private/chat.domain.com.key
    SSLCertificateChainFile /etc/ssl/certs/intermediate.ca.pem

    <Location />
        Require all granted

    RewriteEngine On
    RewriteCond %{HTTP:Upgrade} =websocket [NC]
    RewriteRule /(.*)           ws://localhost:3000/$1 [P,L]
    RewriteCond %{HTTP:Upgrade} !=websocket [NC]
    RewriteRule /(.*)           http://localhost:3000/$1 [P,L]

    ProxyPassReverse /          http://localhost:3000/

PS: Let me know if I should provide additional info.
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James Blond

Joined: 19 Jan 2006
Posts: 6945
Location: Germany, Next to Hamburg

PostPosted: Tue 13 Oct '20 9:59    Post subject: Reply with quote

The only way that I found for ubuntu was


sudo su
source /etc/apache2/envvars
/usr/sbin/apache2 -k graceful
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Joined: 16 Aug 2020
Posts: 84
Location: UK

PostPosted: Tue 13 Oct '20 16:33    Post subject: Reply with quote

James beat me to it. A graceful restart will apply your updated configuration to new connections.

Since websockets are stateful and stay connected, you can't expect Apache to pick up a new configuration and apply it to an existing thread of execution.

Of interest, the current 2.4 series mod_proxy_wstunnel module has no connection timeout option, though I note Apache 2.5 does - https://httpd.apache.org/docs/trunk/mod/mod_proxy_wstunnel.html#proxywebsocketidletimeout.

When that comes along, you will be able to set a timeout for what you consider to be idle connections.
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Joined: 03 May 2021
Posts: 1
Location: Germany,Jena

PostPosted: Mon 03 May '21 17:33    Post subject: Reply with quote

I had the exactly same problem with our RocketChat installation where some websockets seems to stay up forever.
I dont know if this is a design flaw, a bug or maybe even intended. 2.2k open issues at GitHub for RocketChat...awww...waste of time searching for a proper solution. Rolling Eyes
I ended up with a cron job that is running every 8 hours at the backend server, killing the open connections from the apache reverse proxy.
ss -K dst <IP of your apache reverse proxy> and sport 3000

The apache slots went down from 29 to 6 and I did not observed any negative impact to the users.

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