Tag: Automation

ChatOps: Snack Preview Script

November 15, 2015 » Geek

One of the things we’ve built at Pack is Snack, an iOS app which shows users five great dog photos every day.

Ideally, each Snack would be thematic, and curated. However, curation doesn’t always get done. Either no theme is apparent, or we just don’t get to it in time.

When there is no curated snack, we draw from our Editors Picks, a collection of the best dog photos available. This gives us quality content, even when we don’t have the chance to pick all five by hand.

There is a downside to this though. Some of our editors picks are specific to an event or time period. Like Christmas or Halloween photos. These wouldn’t be very good in a Snack in the middle of May.

So how do we balance the light editorial touch while making sure the random snacks are cohesive?

My solution was a preview injected into our chat. Every day a script grabs tomorrows Snack, makes a composite, and sends it into Slack for us to review. If we see something is off, we jump into the admin and fix it.

It’s fairly brute force, but a good example of centralizing tools around chat, which is something we try to do. First we get the photo information, then we download each photo. We take those and use ImageMagick to create a captioned composite. Finally, we upload that to S3 and send the link to Slack.

This first listing is pretty simple. We just send a request for tomorrows Snack JSON from the public API. You might wonder why we don’t just set day_requested to tomorrow, but the API doesn’t support that, and neither does the logic of the app. This runs on a cron job which mails failed runs to us using cronic, so we call raise_for_status() to explicitly fail on bad HTTP requests.

This next section shells out to download each image into a temporary file. Order matters in a Snack, so we use a counter instead of taking random filenames.

ImageMagick is a powerful suite of tools, and in the next block we use the montage command to stitch our photos together.

-title, as you might imagine, lets us write some title text onto the composite. -geometry specifies the size and spacing of each image, 300px square, with 20px of vertical offset from the title. Lastly, -tile lays out the images in a 5 by 1 grid instead of stacking them in the default method.

tinys3 is an awesomely light API to S3 uploads, and then we use the Slack Incoming Webhook integration to send the message to chat.

All in all a simple, effective piece code that drops needed information into our chat every morning. Here’s the whole listing for a complete picture.

And here is an example of a random Snack that needed correction. Problem solved!

Many thanks to tinys3 and requests.

Automatic MySQL Slow Query Log Emails

October 10, 2014 » Geek

Something we try to do regularly at Pack is to check for slow queries.

We do this when introducing new features and schema changes, but we also try to do it occasionally to look for anything that may have slipped through, or become more of an issue as usage patterns change.

To make this a more regular occurrence, I decided to automate it.

The first thing that needed to be handled was enabling and disabling the slow query log. I don’t want it to run all the time, because eventually it will eat up too much disk, and there has to be overhead to calculating and saving that data.

To turn it on and off, I created a limited privilege user on the server called “slow_log”. The commands needed to turn on the slow query log are SET GLOBAL and FLUSH SLOW LOGS. Looking at the MySQL documentation, the privileges needed for those commands are RELOAD and SUPER.

Once that user was in place, I created two shell scripts. The first just logs into MySQL and turns on slow query logging.

The second script turns slow query logging off, then it processes the slow query log with request-log-analyzer and pt-query-digest. Lastly it emails the output of those tools to me.

Finally, I added a cron job to run the first script at the beginning of the day once a month, and another to run the second at the end of the day once a month. That way, once a month, I get an email with slow query logs to look over and try to improve.

As a note, using a subshell to generate the body of the command is something I hadn’t seen before and came across while looking for uuencode usage. It’s a nice trick.

So. What did I screw up horribly?