Middleware System

Prax provides a powerful middleware system for intercepting queries before and after execution. Use middleware for logging, metrics, authentication, caching, retry logic, and more.

Overview

The middleware system allows you to intercept every query before and after execution. Middleware can modify queries, add context, collect metrics, implement caching, and more.

Built-in Middleware

  • • LoggingMiddleware - Query logging with levels
  • • MetricsMiddleware - Performance metrics
  • • TimingMiddleware - Execution time tracking
  • • RetryMiddleware - Automatic retry with backoff

Use Cases

  • • Query logging and debugging
  • • Performance monitoring
  • • Multi-tenant data isolation
  • • Query caching
  • • Circuit breaking

Logging Middleware

Log all queries with configurable detail levels. Automatically detect slow queries and log warnings.

Log Levels

Level Description
Off No logging
Error Only errors
Warn Errors and slow queries
Info All queries (default)
Debug Queries with parameters
Trace Everything including responses

Metrics Middleware

Collect query performance metrics for monitoring and optimization.

Available Metrics

total_queries

Total query count

successful_queries

Successful count

failed_queries

Failed count

avg_time_us

Average time (μs)

slow_queries

Slow query count

cache_hits

Cache hit count

Retry Middleware

Automatically retry failed queries with exponential backoff. Perfect for handling transient errors.

Custom Middleware

Create your own middleware by implementing the Middleware trait.

Query Context

The QueryContext provides information about the current query and allows modification.