Practical Observability

• MiniCrossStitching Rails app
• Contains a mystery defect

Setup

1. Create a new Github Codespace
2. Run server: bin/serve
3. Simulate users: bin/hammer

Commands

bin/setup  # Setup the app
bin/serve  # Start the server
bin/hammer # Simulate users
bin/errors # Show errors in Solid Errors

Code

3. Build

Starting code for logging:

    Rails.logger.info(
      message: "Added border to preview",
      "event.name" => "com.jp.cs.pattern.preview.added",
      "com.jp.cs.pattern.width" => width,
      "com.jp.cs.pattern.height" => height
    )
  rescue StandardError => e
    Rails.logger.error(
      message: "Error adding border to preview",
      "event.name" => "com.jp.cs.pattern.preview.added",
      "com.jp.cs.pattern.width" => width,
      "com.jp.cs.pattern.height" => height,
      exception: e,
    )
    raise e

4. Use

DQL for GROUP BY orientation:

fetch logs
| filter matchesValue(event.name, "com.jp.cs.pattern.preview.added")
| filter isNotNull(com.jp.cs.pattern.orientation)
| summarize count(), by: { loglevel, com.jp.cs.pattern.orientation }