Wednesday, July 24, 2019

HTML5 - video playsinline

I added "autoplay muted" to my <video> tag to make a video autoplay in a carousel. It worked on desktop Chrome or Firefox, but didn't work on iOS Chrome or Safari.

I learned about the "playsinline" fix from here: https://webkit.org/blog/6784/new-video-policies-for-ios/

Adding "playsinline" to my video tag fixed it.

Thursday, July 11, 2019

ESP32 Plant Sensor

I set up a ESP32 houseplant soil water + temperature + humidity + light sensor that sends me a daily status update message.






Wednesday, July 10, 2019

AWS - redirecting domain to url using a 302 redirect (without running a server)

I wanted to make a domain name (heckingoodboys.com) redirect to a multisubreddit for dog pictures, but I didn't want to run a web server for it.

Here's what I did:
  1. Purchase the domain using Route53.
  2. Create two public s3 buckets (www.heckingoodboys.com and heckingoodboys.com)
  3. Enable "Static website hosting" on www.heckingoodboys.com and redirect to heckingoodboys.com.
  4. Enable "Static website hosting" on heckingoodboys.com, select "use this bucket to host this website", and use routing rules similar to this:
    <RoutingRules>
      <RoutingRule>
        <Redirect>
          <Protocol>https</Protocol>
          <HostName>www.reddit.com</HostName>
          <HttpRedirectCode>302</HttpRedirectCode>
          <ReplaceKeyPrefixWith>user/heckingoodboys/m/heckingoodboys/</ReplaceKeyPrefixWith>
        </Redirect>
      </RoutingRule>
    </RoutingRules>
  5. Back to Route53 - Create an A record for both www.heckingoodboys.com and heckingoodboys.com using the alias to their respective buckets. (this will be the first option in autocomplete)
For more details: https://medium.com/@P_Lessing/single-page-apps-on-aws-part-1-hosting-a-website-on-s3-3c9871f126

Why not just use a CNAME from www.heckingoodboys.com to heckingoodboys.com? AWS says they don't charge for aliases, but they do charge for CNAMEs. So, I used an alias to a bucket instead.

Wednesday, February 7, 2018

Django - When To Use Signals?

According to this blog post, almost never: https://lincolnloop.com/blog/django-anti-patterns-signals/

Django - Custom Storage Backends

I just learned about the custom storage systems in Django.

What can you do with custom storage systems?:
"Django abstracts file storage using storage backends, from simple filesystem storage to things like S3. This can be used for processing file uploads, storing static assets, and more." -https://tartarus.org/james/diary/2013/07/18/fun-with-django-storage-backends

Friday, January 19, 2018

Sphinx Search - Lessons Learned

Here are a few things I've learned while working on a project that uses Sphinx search:
  • It's important to know the difference between fields and attributes. Attributes are basically unindexed columns and you should try to avoid filtering only on these columns. Fields support full text search. 
  • It supports its own custom binary protocol and the MySQL protocol (recently they also added a HTTP API). When you see "listen = localhost:9306:mysql41" in the config, that means it's listening for MySQL protocol traffic on port 9306.
  • https://github.com/a1tus/sphinxapi-py3 appears to be the best Python client for the binary api at the moment. This doesn't support INSERTing things into the index (you'll need to use the MySQL protocol for that).
  • The version of sphinxapi-py3 on pypi is a fork with just a few minor fixes and appears to be safe.
  • It does not match partial words by default. Turning on partial matching can also increase the size of your index dramatically. You can also limit the fields that support partial matching with the "infix_fields" and "prefix_fields" setting.
  • Stemmers aren't turned on by default. So, searching for "dog" will not match "dogs".
  • Most special characters ($, @, &, etc) are ignored by default. You will need to add them to charset_table if you want them to be searchable.
  • Ruby's thinking-sphinx looks much more battle tested than all of the Python binary api clients: https://github.com/pat/thinking-sphinx
  • You will need to use a real-time index if you want to INSERT/DELETE records immediately.
  • If you're using a real-time index, you will probably need to increase the "rt_mem_limit" from its default of 128mb. If this limit is too low, you'll see a high number of "disk chunks" when you run the "SHOW INDEX rtindex STATUS" query. More info: http://sphinxsearch.com/blog/2014/02/12/rt_performance_basics/
  • You have to use a special dialect if you want to use SQLAlchemy with sphinx: https://github.com/conversant/sqlalchemy-sphinx
  • This appears to be the best Dockerfile for sphinx: https://github.com/leodido/dockerfiles
I probably won't be using Sphinx search for any new projects. Elasticsearch seems preferable these days.

Monday, December 11, 2017

MySQL - Duplicate Errors & Trailing Whitespace

I had a unique constraint on a VARCHAR column and I inserted two rows with the following values:

  1. "name" (without trailing whitespace)
  2. "name " (with trailing whitespace)

To my surprise, I got a duplicate error on that 2nd insert. It turns out that MySQL ignores that trailing whitespace when it makes comparisons.

The MySQL docs say this: "All MySQL collations are of type PAD SPACE. This means that all CHAR, VARCHAR, and TEXT values are compared without regard to any trailing spaces. “Comparison” in this context does not include the LIKE pattern-matching operator, for which trailing spaces are significant." (https://dev.mysql.com/doc/refman/5.7/en/char.html)

The solution? You should probably be trimming trailing whitespace in your API endpoints and on your front-end.