Server logging for web apps

TheodorosPloumis.com / @theoploumis

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Get them: online presentation / source code

Under Attribution 4.0 International license. Icons by icons8.

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What is this talk about

• What is logging
• Why we need logging
• Common logging formats
• Logging examples
• Logging tools

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What is logging

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Why we need logging

• Protect our app
• Know what is going on
• Know our visitors
• Plan our resources & needs
• Data is Data

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How it works

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Log format variables

<1. IP/domain> <2. user> <3. datetime> <4. request> <5. http-status> \
<6. request-size> <7. referrer> <8. user-agent> <9. request-time>

IP: 62.109.16.162
user: -
datetime: [26/Feb/2019:00:11:13 +0200]
request: "GET /index.php HTTP/1.1"
http-status: 200
request-size: 20702
referrer: "/user/login"
user-agent: "Mozilla/5.0 ... Chrome/43.2357.125 Safari/537.36"
request-time: 0.4

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Common log formats

// Common Log Format (CLF)
"%h %l %u %t \"%r\" %>s %b"

// Common Log Format with Virtual Host
"%v %h %l %u %t \"%r\" %>s %b"

// Extended/combined log format
"%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-agent}i\""

// Referer log format
"%{Referer}i -> %U"

// Agent (Browser) log format
"%{User-agent}i"

See apache log formats.

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Logging examples

• Real logs

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Open source logging tools

• rsyslog
• graylog
• logwatch/ELK stack
• logstash
• fluentd
• ... many non open-source tools

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Tips

• include a timestamp
• format in JSON
• don't log insignificant events
• log all application errors
• write messages in a human-readable form
• don't log informational data in production
• don't log anything a human can't read or react to
• if you save logs use a nosql database

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Demo

• demo

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Thank you!

Join Serres Hackathon 2019 11 & 12 May 2019

Questions?