Logging & Tracking

Jazzy includes a modern, structured logging system that provides clear visibility into your application’s behavior and performance.

Request ID

Every request processed by Jazzy is automatically assigned a unique, UUID-like Request ID. This ID is crucial for tracking a single user’s journey through your logs and across distributed systems.

Accessing Request ID

You can access the current Request ID anywhere within your handlers using ctx.requestId.

import jazzy

Route.get("/", proc(ctx: Context) {.async.} =
  let rid = ctx.requestId
  ctx.text("Your unique request ID is: " & rid)
)

Jazzy also automatically adds an X-Request-Id header to every response.

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Structured Logging

Jazzy’s built-in logger provides color-coded, structured terminal output for every incoming request.

Log Output Example

2026-04-06 15:42:01 [INFO] GET /api/users - 200 OK (12ms) [rid: 550e8400-e29b-41d4-a716-446655440000]
2026-04-06 15:42:05 [DEBUG] Cache HIT for key: user_profile_1
2026-04-06 15:42:10 [ERROR] Failed to connect to database [rid: 550e8400-e29b-41d4-a716-446655440001]

Configuration

You can control the verbosity of your logs by setting the LOG_LEVEL in your .env file.

# Possible values: DEBUG, INFO, WARN, ERROR, FATAL, NONE
LOG_LEVEL=INFO

The logger automatically adapts to your environment:

• Development: Full color-coded output for better readability.
• Production: Clean output suitable for log aggregators and cloud environments.

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Custom Logs

You can also use Jazzy’s logger for your own application logic.

import jazzy/core/logger

Log.info("Starting the worker process...")
Log.warn("User is attempting to access restricted data!")
Log.error("Unexpected error in calculation module")