PHPDD23: Practical Debugging and Performance Profiling

Finding and fixing bugs is part of the daily work in software development.
This talk is about a methodical approach to finding bugs.
In particular, we will focus on performance profiling, as there are particular challenges here, and some of the common debugging tools such as XDebug are of limited use.
We will discuss various tools as well as their use to efficiently track down performance issues.
We will look at the whole stack of the application, including IO and database.

Transcript

1. Practical Debugging and Performance Pro fi ling #PHPDD23
3. Photo by Stackie Jia on Unsplash Flow in which a person [….] is fully immersed in a feeling of energized focus, full involvement, and enjoyment in the process of the activity.
8. { "name": "neos/neos-development-distribution", "description": "Neos Development Distribution", "license": "GPL-3.0-or-later", "support": { "email": "hello@neos.io", "slack": "http://slack.neos.io/", "forum": "https://discuss.neos.io/", "wiki": "https://discuss.neos.io/c/the-neos-project/project-documentation", "issues": "https://github.com/neos/neos-development-collection/issues", "docs": "http://neos.readthedocs.io/", "source": "https://github.com/neos/neos-development-distribution" }, "config": { "vendor-dir": "Packages/Libraries", "bin-dir": "bin", "preferred-install": { "neos/*": "source", "flowpack/*": "source" }, "allow-plugins": { "neos/composer-plugin": true } }, "require": { "neos/neos-development-collection": "8.0.x-dev", "neos/flow-development-collection": "8.0.x-dev", "neos/demo": "8.0.x-dev", "neos/neos-ui": "8.0.x-dev", "neos/neos-ui-compiled": "8.0.x-dev", "neos/fusion-form": "@dev", "neos/party": "@dev", "neos/seo": "@dev", "neos/imagine": "@dev", "neos/twitter-bootstrap": "@dev", "neos/form": "@dev", "neos/setup": "@dev", "flowpack/neos-frontendlogin": "@dev", "mikey179/vfsstream": "^1.6", "phpunit/phpunit": "^9.0", "symfony/css-selector": "^2.0", "symfony/css-selector": "^2.0", "vimeo/psalm": "~4.9.3", "neos/doctools": "^3.3" }, "repositories": { "distributionPackages": { "type": "path", "url": "./DistributionPackages/*" } }, "suggest": { "ext-pdo_sqlite": "For running functional tests out-of-the-box th }, "scripts": { "post-create-project-cmd": "./flow welcome", "post-update-cmd": "Neos\\Flow\\Composer\\InstallerScripts::postU "post-install-cmd": "Neos\\Flow\\Composer\\InstallerScripts::post "post-package-update": "Neos\\Flow\\Composer\\InstallerScripts::p "post-package-install": "Neos\\Flow\\Composer\\InstallerScripts:: "test-unit": "phpunit -c Build/BuildEssentials/PhpUnit/UnitTests. "test-functional": "phpunit -c Build/BuildEssentials/PhpUnit/Func "test-static-flow": "psalm --config=Packages/Framework/psalm.xml "psalm-baseline-update-flow": "psalm --config=Packages/Framework/ Framework/psalm-baseline.xml" }, "require-dev": { "neos/behat": "8.0.x-dev", "neos/buildessentials": "8.0.x-dev" } }
9. ? ???
11. "bin-dir": "bin", "preferred-install": { "neos/*": "source", "flowpack/*": "source" }, "allow-plugins": { "neos/composer-plugin": true } }, "require": { "neos/neos-development-collection": "8.0.x-dev", "neos/flow-development-collection": "8.0.x-dev", "neos/demo": "8.0.x-dev", "neos/neos-ui": "8.0.x-dev", "neos/neos-ui-compiled": "8.0.x-dev", "neos/fusion-form": "@dev", "neos/party": "@dev", "neos/seo": "@dev", "neos/imagine": "@dev", "neos/twitter-bootstrap": "@dev", "neos/form": "@dev", "neos/setup": "@dev", "flowpack/neos-frontendlogin": "@dev", "mikey179/vfsstream": "^1.6", "phpunit/phpunit": "^9.0",
12. OSX Host System Docker Container(s) fi le mounts my model of reality
13. OSX Host System Linux Virtual Machine Docker Container(s) mounts no problem, without performance hit normal mounts not possible, !!! lots of workarounds for emulating mounting SLOW sshfs gRPC-fuse virtiofs reality
14. OSX Host System Linux Virtual Machine Docker Container(s) application source code cache fi les vendored source code
15. Method
16. Stable Foundation Hypothesis Design Experiment Execute Experiment Valid Knowledge write it down must give 100% reliable results
17. Unstable Foundation Modify some things in the codebase "which might improve things" do roughly the same steps, but not exactly
18. Use Production Data for Debugging / Pro fi ling prepare for non-linear behavior
19. What tools do we have available to design experiments? ... to generate validated knowledge
20. var_dump() die() am I in the right codebase? (die() in entrypoint) 
 am I in the right fi le? 
 is the opcache caching too agressively? 
 how often is this method called?
21. drydock execroot: enter a container as root
22. kill -USR2 [php-fpm] modify server con fi g re-read the PHP con fi g and restart
23. function B.2 throw new \RuntimeException("FOO"); read a stack trace function A function B.1 function C function main function main() { a() } function a() { b1(); b2(); } function b1() { c () } Stack
24. throw new \RuntimeException("FOO"); read a stack trace
25. xdebug_break() drydock xdebug [container] install xdebug into a running container
26. My code is slow...
27. Flame Graph
28. PHP-SPX
29. PHP-SPX drydock spx [container] install spx into a running container
30. Linux Kernel your program File IO System Calls Network IO current time
31. strace apt-get install strace (as root) strace -p [pid]
34. bpftrace
35. bpftrace
36. Summary
37. Stable Foundation Hypothesis Design Experiment Execute Experiment Valid Knowledge write it down run an experiment to establish foundation must give 100% reliable results
38. Thanks! Daniel Kahnemann: Thinking Fast and Slow xdebug, PHP-SPX github: sandstorm/drydock github: sandstorm/ebpf-tracer