Roy Tang

roytang.net

Programmer, engineer, scientist, critic, gamer, dreamer, and kid-at-heart.

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I recently did a server migration since I moved to new hosting, The move was from managed/shared hosting to a VPS, these are some notes I took during the process, which I figure might be helpful if I ever tried to do this again. (And maybe someone else finds it helpful too). Links and references to helpeful resources are included.

Setting up a webserver and WSGI container

I already knew I wanted to use Nginx (managed hosting on the old server always used Apache), that meant needing to choose a WSGI container for the Django apps. The choices were either gunicorn or uwsgi. Readings suggest minimal performance difference between the two. I did try setting up both, and found uwsgi's setup much more straightforward and with more helpful step-by-step documentation: https://uwsgi-docs.readthedocs.io/en/latest/tutorials/Django_and_nginx.html

Nginx itself was pretty straightforward to set up. This "common pitfalls" article was helpful in resolving issues: https://origin-www.wp.nginx.com/resources/wiki/start/topics/tutorials/config_pitfalls/.

One thing I will note that's not in the article above is that for static files to be served by Nginx, it was easier to just have everything be under /var/www, for permission purposes. I initially had static files in a different folder in my user root, but really there's no reason for that since you're going to serve them statically anyway.

Setting up PHP on Nginx

I needed PHP since I had a few minor scripts/pages and a Wordpress install that needed PHP. For the setup on Nginx, I found this guide from askubuntu super helpful: https://askubuntu.com/questions/134666/what-is-the-easiest-way-to-enable-php-on-nginx

This guide from DigitalOcean was also helpful: https://www.digitalocean.com/community/tutorials/how-to-install-linux-nginx-mysql-php-lemp-stack-in-ubuntu-16-04

I was encountering some issues with fastcgi not mapping requests to the correct PHP script if the Nginx location block was aliased. This was with me using the default snippets/fastcgi-php.conf that was provided with the fastcgi install. I resolved the issue by adding an additional fastcgi_param to the php location block like so:

    location /sample-path {
        alias /var/www/sample-path;
        # autoindex on;

        location ~ \.php$ {
                include snippets/fastcgi-php.conf;
                fastcgi_param  SCRIPT_FILENAME    $request_filename;
                fastcgi_pass unix:/run/php/php7.4-fpm.sock;
        }
    }

The solution for this came from the Nginx common pitfalls article listed above.

Choosing a database

I initially wanted to use PostgreSQL (since that's what I was using locally) and set that up first. Then I realized I had a Wordpress install I wanted to carry over, and apparently Wordpress needs MySQL, so oops. I didn't want to have two databases running, so that was out. Plan out your database usage boys.

Setting up MySQL for Django

I created the initial MySQL database with character set utf8, which apparently had the dumb implementation of only supporting 3 bytes for multibyte characters. This led to errors when I tried importing records into Django that had emojis and the like in text. Apparently the "correct" character set to use is utf8mb4 (mb4 -> "multibyte 4" I guess?). It's kinda dumb that they had to invent a "more utf8 character set" because of their initial dumb implementation. It's also dumb that I didn't realize this when apparently the MySQL databases on the old server were already using utf8mb4! On the Django side, you need to specify the charset in the database settings. Helpful for resolving this issue was donturner's answer on this SO question: https://stackoverflow.com/questions/2108824/

After some initial testing, I also encountered a "MySQL has gone away" every so often. Turns out Django was holding on to connections for too long, so a timeout had to be set in the database settings as well. SO reference: https://stackoverflow.com/questions/26958592/

Edit: I just encountered this a few hours after I wrote this post, when I tried to make the site display all times in Manila local time. Apparently, even if I set my Django app to be timezone, aware, additional setup needs to be done on the MySQL side so it knows what the actual timezones are (feels like they should really do this as part of the install!). Basically you need to run mysql_tzinfo_to_sql to load the OS timezone info into the database. This is in the Django documentation and the MySQL documentation.

Misc stuff

I used cron to set up most of the batch jobs I usually run (like the Twitter bots, etc). Initially I had problems where it seemed like cron wasn't running the jobs, even though syslog showed me the cron daemon was actually running. I don't have notes on how I resolved this, but mentioning it here so that if this happens again in the future, I know to actuall take notes!

Setting up log files for my cron jobs: I did it this way: 0 * * * * /path-to-batch/hourly.sh >> /var/log/cron/my-log-file.log 2>&1. The "2>&1" at the end is necessary so that stderr is redirected to the same file (otherwise you'd only get stdout).

Log rotation: these is the kind of thing you don't realize you need to do when you're managing your own server. Anyway, I found this guide helpful: https://linoxide.com/linux-how-to/setup-log-rotation-logrotate-ubuntu/

I needed to set up AWStats on the new server (and migrate data from the old server). This guide was helpful: https://larsee.com/blog/2020/06/awstats-on-ubuntu-20-04-with-nginx/

When migrating the old AWStats data files, the filename format from the oldserver was slightly different (new install needed to end with *.roytang.net.txt), so I learned a bit of bash scripting to do the batch rename:

for i in /path-to-tmp/awstats/*.txt ; do cp "$i" "/path-to-tmp/awstats/out/$(basename "$i" .txt).roytang.net.txt" ; done

Setting up Let's Encrypt SSL on Nginx: https://www.nginx.com/blog/using-free-ssltls-certificates-from-lets-encrypt-with-nginx/

Lessons learned

One thing I didn't expect from the migration from shared hosting to a VPS is how much memory I'd need. My old hosting plan was only on 512MB ram, and the lowest DigitalOcean droplet had 1GB RAM, so I figured that was fine! But MySQL occasionally had out of memory errors on startup even at 1GB ram, so I bumped up to the next level (2GB RAM). I guess the database RAM usage didn't count against my limits on the shared hosting! The next tier isn't much more expensive and is still manageable for my casual/hobby hosting purposes, but I will probably try to look into more detail into the memory situation at some point to see what I can optimize.

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Last modified at: Nov. 5, 2020, 4:14 p.m.. Source file