This document discusses system level debugging tools Strace and Sysdig for debugging PHP applications. Strace allows seeing system calls with low overhead, while Sysdig provides protocol awareness and container visibility. Both tools can help debug slow scripts, PHP-FPM issues, and network problems. Sysdig integrates chisels for parsing raw data and supports debugging containers and network traffic. The document recommends using Strace when you lack root access and Sysdig when watching network activity or containers.

1. DEBUGGING PHP WITH
STRACE AND SYSDIG
JOSHUA EICHORN
CTO PAGELY

2. WHAT
• System level debugging tools
• See system calls
• See network/disk io

3. WHY
• IO is the most common cause of problems
• No overhead when not in use
• Much lower overhead then newrelic/etc
• Easy install

4. STRACE
• Easy install
• Apt-get install etc
• See system calls
• Lots of filters
• Output is raw

5. SYSDIG
• Needs a kernel module
• Easy install on anything new
• Protocol aware http etc
• Container aware
• Easy to see all the traffic on port 80 or 9000

6. DEBUGGING A CLI SCRIPT
• Trace script
• Watch a script with no status
• See mysql queries

7. DEBUGGING PHP-FPM
• Broken config, see fpm headers
• Log messages with broken logging
• Finding a slow http request

8. SYSDIG AND CHISELS
• Scripts to parse raw data
• Protocol decoding
• Summary

9. NETWORK DEBUGGING WITH SYSDIG
• Http traffic/http chisel
• PHP-fpm traffic
• Filter to just POST requests
• From a specific IP
• Using with SSL

10. SYSDIG AND CONTAINERS
• See network io in a container
• See disk io in a container
• Snoop on tty activity

11. SYDIG LINKS
• http://www.sysdig.org/wiki/sysdig-user-guide/
• http://www.sysdig.org/wiki/sysdig-examples/

12. WHEN TO USE EACH TOOL
• Strace
• When you don’t have root
• Finding general slowness
• Broken configs
• What is that script doing
• Sysdig
• Watching network traffic
• What is that container doing
• You want tcpdump

13. IS HIRING DEVOPS ENGINEERS
• Want to use Strace and Sysdig on the job
• Join Pagely’s Devops Team
• https://pagely.com/careers/devops-engineer-remote-jr-mid/