SimpleApm (Rails Engine)

A lightweight Redis-backed Rails engine for web request performance monitoring and slow request tracing.

SimpleApm records request performance by day:

• The slowest requests, 500 by default.
• The slowest 20 requests for each action.
• Average response time for each action.
• Slow request details and related SQL details, trimming excess records.
• Average and slowest response time, request count, and other metrics in 10-minute intervals, with charts.
• External HTTP request duration during each request.

The web UI supports English and Chinese. English is used by default, and users can switch languages from the top-right corner.

Action and request detail pages include Copy for AI with a JSON preview. Request reports include metadata, timings in seconds, memory in MB, retained SQL and external HTTP calls with code locations. Action reports add daily aggregates and the retained fastest, slowest and slow request samples, marking unavailable details explicitly. Common credential fields and SQL string literals are filtered; reports describe collection thresholds and sampling limits. Clipboard copying includes a fallback for HTTP deployments and manual selection when browser copying is unavailable.

Lists support search and precise duration sorting. Slow requests offer a sample limit and refresh controls, while date-aware links keep the selected day's context across pages. Data cleanup and collection controls use POST forms with confirmation for destructive operations.

SimpleApm records request-level data around Rack and uses Redis for storage and aggregation.

The core data flow is based on Active Support Instrumentation.

Instrumentation events are processed by a long-running worker thread so request handling does not block on metric aggregation.

Memory usage is collected with get_process_mem. In Linux testing, collection takes less than 1 ms.

• Dashboard

• Slow Requests

• Action List

• Request Info

• Action Info

• Data Management

Mount the engine in your Rails routes:

# routes.rb
mount SimpleApm::Engine => "/apm"

Or run the installer:

rails generate simple_apm:install

Add this line to your application's Gemfile:

gem "simple_apm"

Then run:

bundle

Issues and pull requests are welcome.

The gem is available as open source under the terms of the MIT License.