Twelve-Factor App | Treat Logs as Event Streams

The eleventh factor of the Twelve-Factor App methodology emphasizes treating logs as event streams.

Why Treat Logs as Event Streams?

Treating logs as event streams means considering logs as continuous events rather than static files. This approach offers several benefits:

  • Real-Time Analysis: Enables real-time monitoring and alerting.
  • Flexibility: Facilitates integration with various log processing and monitoring tools.
  • Scalability: Supports efficient handling of large volumes of log data.

How to Treat Logs as Event Streams

Write Logs to Standard Output

Applications should write logs to standard output, allowing them to be collected and processed by the surrounding environment.

Example: Logging in a Python Application
import sys

print("Info: Application started", file=sys.stdout)
Utilize Log Aggregation Tools

Tools like Fluentd, Logstash, or Splunk can collect, process, and analyze log streams.

Example: Forwarding Logs with Fluentd

Fluentd configuration to collect logs and forward them to Elasticsearch:

  @type forward
  port 24224

<match **>
  @type elasticsearch
Implement Centralized Logging

Centralized logging systems provide a unified view of logs across different services and environments.

Deployment Strategies with Logs

Logs play a critical role in monitoring, troubleshooting, and analytics.

  • Development Stage: Implement proper logging practices in the application code.
  • Deployment Stage: Set up log aggregation and processing tools.
  • Monitoring Stage: Create dashboards, alerts, and analysis based on log data.

Treating logs as event streams aligns with modern, distributed system design.