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I use nginx as a reverse proxy. Whenever I update the config for it using

sudo "cp -r #{nginx_config_path}* /etc/nginx/sites-enabled/"
sudo "kill -s HUP `cat /var/run/nginx.pid`"

I face a brief downtime. How can I avoid that?

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2 Answers 2

up vote 33 down vote accepted

Run service nginx reload or /etc/init.d/nginx reload

It will do a hot reload of the configuration without downtime. If you have pending requests, then there will be lingering nginx processes that will handle those connections before it dies, so it's an extremely graceful way to reload configs.

Sometimes you may want to prepend with sudo

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Both of those should do exactly what the question states: send SIGHUP to the nginx master process. There should not be a difference. nginx.org/en/docs/control.html –  Gnarfoz Jul 27 '12 at 12:36
When I issue the command on CentOS it keeps saying "Usage /etc/init.d/nginx (start..stop...restart..reload)" .. and that's exactly how I used it. Within the file /init.d/nginx I found kill -HUP cat $PIDFILE || echo -n " can't reload" –  mashup Apr 13 at 18:21

Usually, reloading configuration file of a service should not affect the running service. However, this depends on how the SIGHUP signal is processed.

If a specific service is experiencing a downtime during reload, this can be circumvented by running the same service on multiple servers preferably using a load balancer. In this case, you can take out one server at a time and reload/restart it. Then, it can be re-added after confirming it is OK.

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While this does not directly answer the question, this is definitely a best-practice scenario that the OP would be smart to follow for avoiding downtime in general. –  Andrew M. Apr 11 '12 at 17:29
Details on how nginx handles different signals: nginx.org/en/docs/control.html –  Gnarfoz Jul 27 '12 at 12:37

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