nginx - if current hour is between

Question

I want to disable the access to an app during a certain period of the day.

Is it possible to do something like this in Nginx?

if(hour > '04:00:00' && hour < '05:00:00') {
    root /var/www/maintenance;
} else {
    root /var/www/site;
}

Answer 1

I can only think of 2 ways of doing this (other than the cron changing the symlink):

1) http://nginx.org/en/docs/http/ngx_http_ssi_module.html#variables

2) Create a very small PHP/Python/Whatever app that returns 200 if not maintenance hours and 403 otherwise. Use the http auth module. http://nginx.org/en/docs/http/ngx_http_auth_request_module.html

Answer 2

Just create a bash script to update a file and set it as a cronjob, e.g:

#!/usr/bin/env bash

SiteStatus="$1"
SiteStatusConfig="/etc/nginx/status.conf"

if [ "$SiteStatus" = "maintenance" ]; then
    echo "root /var/www/maintenance;" > $SiteStatusConfig
else
    echo "root /var/www/site;" > $SiteStatusConfig
fi
nginx -s reload

Then just place into your nginx site config (replacing root directive):

include status.conf;

Then the cronjob:

0 4 * * * /opt/scripts/nginx-site-script.sh maintenance
0 5 * * * /opt/scripts/nginx-site-script.sh

Trying to do this in nginx, via an if statement and the like can slow nginx down as nginx evaluates the server block (stored in memory) with each request.

Answer 3

The approach I typically use for this is to include a downtime handler whenever I first enable an app in nginx. Here's example config:

location /app_1/ {
    proxy_pass http://127.0.0.1:8001/;
    proxy_set_header   Host             $host;
    proxy_set_header   X-Forwarded-For  $proxy_add_x_forwarded_for;
    error_page 502 =200 /502-app_1-maintenance.html;
}
location /502-app_1-maintenance.html {
    root /var/www/html/error;
    try_files $uri /502-app_1-maintenance.html;
}

Whenever nginx cannot connect to app_1 on port 8001, it produces a 502 error. That error is redirected via error_page 502 =200 /502-app_1-maintenance.html; to a custom page in the second location block that contains a simple "App 1 Under Maintenance" message. Visitors will get this custom "Under Maintenance" page any time app_1 is down. That seamlessly handles unscheduled as well as scheduled downtimes.

In this example, the response code to the user for this maintenance page is a 200 (OK), however, you can change that to an error response if you prefer by changing =200 to the return code of your choice.

You can also add a bit of javascript to have the page reload periodically. Since the url of the maintenance page is the same as the app's url, when app_1 comes back online, it will replace the maintenance page on the next auto-reload.

In your case, since you want to disable public access during certain times, you could combine this nginx configuration with a scheduled app shutdown via crontab. If you wanted, you could then bring your app up on a different port while you perform maintenance. As long as it's not listening on its usual port, visitors will see the Under Maintenance page.