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Automatic Performance Checks: Builds

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Head back to https://blackfire.io, click "Environments" and click into our "Sasquatch Sightings Production" environment.

Interesting. By default, it takes us not to the profiles tab... but to a tab called "Builds". And, look on the right: "Periodic Builds": "Builds are started every 6 hours"... which we could change to a different interval.

Further below, there are a bunch of "notification channels" where you can tell Blackfire that you want to be notified - like via Slack - of the results of this "build" thingy.

Hello Builds

Ok, what the heck is a build anyways? To find out, let's trigger one manually, then stand back and see what happens. Click "Start a Build". The form pre-fills the URL to our site... cool... and we can apparently give it a title if we want. Let's... just start the build.

This takes us to a new page where.... interesting: it's running an "Untitled Scenario"... then it looks like it went to the homepage... and created a profile?

Let's... back up: there are a lot of interesting things going on. And I love interesting things!

First, we've seen this word "scenario" before! Earlier, we used the blackfire-player: a command-line tool that's made by the Blackfire people... but can be used totally outside of the profiling tool. We created a scenario.bkf file where we defined a scenario and used the special blackfire-player language to tell it to go to the homepage, assert a few things, then click on the "Log In" link and check something else:

20 lines | scenario.bkf
name "Various scenarios for the site"
# override with --endpoint option
endpoint "https://localhost:8000"
name "Basic Visit"
visit url("/")
name "Homepage"
expect status_code() == 200
expect css("tbody.js-sightings-list tr").count() > 10
# won't work until we're using Blackfire environment
assert metrics.sql.queries.count < 30
click link("Log In")
name "Login page"
expect status_code() == 200
// ... lines 19 - 20

At that time, this was a nice way to "crawl" a site and test some things on it. The "build" used the same "scenario" word. That's not an accident. More on that soon.

Build "URLs to Test"

The second important thing is that this profiled the homepage because, when we created our environment, we configured one "URL to test": the homepage. That's what the build is doing: "testing" - meaning profiling - that page.

Let's add a second URL. One other page we've been working on a lot is /api/github-organization: this JSON endpoint. Copy that URL and add it as a second "URL to test". Click save... then manually create a second build.

Like before, it creates this "Untitled Scenario" thing. Ah! But this time it profiled both pages! The build also shows up as green: the build "passed".

This is a critical thing about builds. It's not simply that a build is an automated way to create a profile for a few pages. That would be pretty worthless. The real value is that you can write performance tests that cause a build to pass or fail.

Check it out "1 successful constraint" - which is that "HTTP Requests should be limited to 1 per page". Hey! That's the "test" that we set up inside .blackfire.yaml!

6 lines | .blackfire.yaml
"HTTP Requests should be limited to 1 per page":
path: "/.*"
- "metrics.http.requests.count <= 1"

The real beauty of tests is not that the "Assertions" tab will look red when you're looking inside a profile. The real beauty is that you can configure performance constraints that should pass whenever these builds happen. If a build fails - maybe because you introduced some slow code - you can be notified.

Build Log: blackfire-player

But there's even more cool stuff going on. Near the bottom, click to see the "Player output". Woh! It shows us how builds work behind-the-scenes: the Blackfire server uses the blackfire-player!

Look closer: it's running a scenario: visit url(), method 'GET', then visit url() of /api/github-organization. It's a bit hard to read, but this converted our 2 "URLs to test" into a scenario - using the same format as the scenario.bkf file - then passed that to blackfire-player. You can even see it reloading both pages multiple times to get 10 samples. That's one of the options it added in the scenario.

So with just a tiny bit of configuration, Blackfire is now creating a build every 6 hours. Each time, it profiles these 2 pages and, thanks to our one test, if either page makes more than one HTTP request, the build will fail. By setting up a notification, we'll know about it.

The fact that the build system uses blackfire-player makes me wonder: instead of configuring these URLs, could we instead have the build system run our custom scenario file? I mean, it's a lot more powerful: we can visit pages, but also click links and fill out forms. We can also add specific assertions to each page... in addition to our one "global" test about HTTP requests.

The answer to this question is... of course! And it's where the build system really starts to shine. We'll talk about that next.

History & Graphs from Automated Builds

But before we do, I want you to see what the build page looks like once it's had enough time to execute a few automated builds. Let's check out the SymfonyCasts environment. Woh! It's graph time! Because this environment has a history of automated builds, Blackfire creates some super cool graphs: like our cache hit percentage and our cache levels. You can see that my OPcache Interned Strings Buffer cache is full. I really need to tweak some config to increase that.

I can also see how the different URLs are performing over time for wall time, I/O, CPU, Memory & network as well as other stuff. We can click to see more details about any build... and even look at any of its profiles.

Anyways, next: let's make the build system smarter by executing our custom scenario.