About

A log is a text file with:

• a timed list of message (activities)
• that an application has performed

Example

• execution/request log:
  • web server:
    • web log (Apache - Web Log (Activity Log) - that stores the Http request
    • error
  • cron
• connection log:
  • ftp
  • ssh (/var/log/secure)

Usage

• Debugging: Inserting log statements into code is a low-tech method for debugging it.
• Monitoring
• For data log as a fault tolerance purposes (Undo/Redo) in a database. See Data Management - (Transaction|Request|Commit|Redo) Log
• Analytics: Because it's hard to know in advance what data might be useful to analyze, a common approach is to log it all and sort through it later.
• Distributed Services: Distributed - Tracing
• Security: The log activity can be monitored in order to track suspicious activity (example ssh login for instance)

Structure

The basic structure of a log entry is:

• a timestamp
• a text message
• optional extra attributes

Server Application

Because:

• they are point in time event registration, they fall in the category of time serie
• they stores text message, the log platorms are specialized search engine.

Documentation / Reference

• ACM The logic of Logging
• wiki/Server log
• wiki/Logfile