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Recording Footage of Myself Investigating a Performance Issue


Of the exercises I attain as segment of Getting Dramatically Higher as a Programmer my authorized is this one. Every week I yarn my display cloak cloak and later review the footage. I’ve discovered this to be a huge manner to be conscious where I’m wasting time and how I could likely resolve the the same blueprint more successfully.

On this write up I’m going to tear over one section of footage of myself. In sigh I’m going to portion:

  • The blueprint I used to be engaged on.
  • A breakdown of where I spent my time when engaged on the blueprint.
  • Frequent tactics I’ve come up with that would accept as true with diminished the duration of time it took to resolve the blueprint.

Since I reviewed myself doing a blueprint at work, I’m unable to portion the raw footage. I am in a reputation to portion my notes on what I used to be doing at every point in time which it’s good to likely moreover see here.

Doing this write up is both for forcing me to present to others what I learned and for others to see what classes I’ve learned.

The Hassle

The footage I reviewed was of myself doing an investigation at work. For several minutes, our p95 for queries went up by an show of magnitude. I’m typically the person accountable for investigating the blueprint and springing up with a approach to close the blueprint within the waste.

To come up with some background, I work for Heap. Heap is a instrument that people can use to flee analytics on their internet blueprint. We give clients a part of Javascript they build on their internet blueprint which allows us to acquire details from their internet blueprint. Our clients can then flee queries over their details. They’ll request questions equivalent to “what number of of us visited my internet blueprint closing week” or “of folks who signed up, how a lot of them went by the tutorial”.

It’s these types of queries that had been insensible for a immediate timeframe.

Since performance is so crucial to Heap, we’ve built a plethora tools for analyzing performance. One in all basically the most grand tools we’ve built is a instrument known as “Perf Tag”. Perf Tag  gathers details about every request ran in our database. It details the request opinion aged to construct the request, besides how noteworthy time was spent in every stage of the request. It then writes this details to a SQL database so it’s that it’s good to likely moreover envisage to request the tips with SQL. Must you indulge in to must be taught more about Perf Tag, I wrote a weblog put up for Heap that covers it intensive.

One in all basically the most typical makes use of of Perf Tag is debugging points upright indulge in this one.

The build the Time Went

In total, it took 25 minutes to settle the foundation position off and write it up. The muse position off was a neighborhood of computationally dear queries had been ran together.

To be more explicit, there could be a particular form of request Heap supports that consumes a lot of resources on our master database. Every request we flee goes by our master database. If our master database turns into overloaded with queries, the duration of time the master DB spends processing queries will tear up.

I made up my mind this was the foundation position off by two indicators. In accordance with Perf Tag, the amplify in request time got here from queries spending more time in our master database. I also checked out the CPU usage of our master database and seen a huge spike in CPU usage across the time of the incident.

In finding the foundation position off, most of my time was spent in a single in every of following three categories:

  • 9 minutes – Having a see at a lot of objects of details. This contains both Perf Tag details and a lot of dashboards.
  • 8 minutes – Writing or debugging SQL queries. The indispensable SQL request I wrote was for the Perf Tag details for queries across the time of the incident.
  • 5 minutes – Writing up the finally ends up in a doc.


In maintaining with the footage, there are two indispensable takeaways I truly accept as true with:

  • When details, I could likely perchance moreover restful accept as true with a transparent sense of what I’m shopping for.
  • I could likely perchance moreover restful accept as true with a repository of fashioned SQL snippets I use.

For the first point, I seen that I’d utilize a lot of time scrolling by the tips with out shopping for the relaxation in sigh. Scrolling mindlessly by the tips wasted a lot of time and I didn’t truly fetch the relaxation particularly provocative. I accept as true with if I had a transparent sense of what I used to be shopping for when digging by the tips, I could likely accept as true with diminished the duration of time I spent wanting by the tips.

As for the 2nd point, I spent a lot of time getting the SQL request I wrote to work. The SQL request I wrote for analyzing the Perf Tag details is similar to many queries I’ve written within the previous. It took an very correct duration of time getting the SQL request to work and debugging some points with it. If I kept a repository of fashioned SQL snippets I aged, I wouldn’t accept as true with wanted to utilize as noteworthy time writing the SQL. This is since the repository would already accept as true with a snippet that labored and was already debugged.

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