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https://github.com/bitechdev/ResolveSpec.git
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Code sanity fixes, added middlewares
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372
pkg/middleware/README.md
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372
pkg/middleware/README.md
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# Middleware Package
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HTTP middleware utilities including rate limiting.
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## Rate Limiting
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Production-grade rate limiting using token bucket algorithm.
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### Quick Start
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```go
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import "github.com/bitechdev/ResolveSpec/pkg/middleware"
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// Create rate limiter: 100 requests per second, burst of 20
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rateLimiter := middleware.NewRateLimiter(100, 20)
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// Apply to all routes
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router.Use(rateLimiter.Middleware)
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```
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### Basic Usage
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```go
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package main
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import (
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"log"
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"net/http"
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"github.com/bitechdev/ResolveSpec/pkg/middleware"
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"github.com/gorilla/mux"
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)
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func main() {
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router := mux.NewRouter()
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// Rate limit: 10 requests per second, burst of 5
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rateLimiter := middleware.NewRateLimiter(10, 5)
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router.Use(rateLimiter.Middleware)
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router.HandleFunc("/api/data", dataHandler)
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log.Fatal(http.ListenAndServe(":8080", router))
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}
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```
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### Custom Key Extraction
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By default, rate limiting is per IP address. Customize the key:
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```go
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// Rate limit by User ID from header
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keyFunc := func(r *http.Request) string {
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userID := r.Header.Get("X-User-ID")
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if userID == "" {
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return r.RemoteAddr // Fallback to IP
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}
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return "user:" + userID
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}
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router.Use(rateLimiter.MiddlewareWithKeyFunc(keyFunc))
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```
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### Advanced Key Functions
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**By API Key:**
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```go
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keyFunc := func(r *http.Request) string {
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apiKey := r.Header.Get("X-API-Key")
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if apiKey == "" {
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return r.RemoteAddr
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}
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return "api:" + apiKey
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}
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```
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**By Authenticated User:**
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```go
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keyFunc := func(r *http.Request) string {
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// Extract from JWT or session
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user := getUserFromContext(r.Context())
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if user != nil {
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return "user:" + user.ID
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}
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return r.RemoteAddr
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}
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```
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**By Path + User:**
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```go
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keyFunc := func(r *http.Request) string {
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user := getUserFromContext(r.Context())
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if user != nil {
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return fmt.Sprintf("user:%s:path:%s", user.ID, r.URL.Path)
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}
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return r.URL.Path + ":" + r.RemoteAddr
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}
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```
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### Different Limits Per Route
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```go
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func main() {
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router := mux.NewRouter()
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// Public endpoints: 10 rps
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publicLimiter := middleware.NewRateLimiter(10, 5)
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// API endpoints: 100 rps
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apiLimiter := middleware.NewRateLimiter(100, 20)
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// Admin endpoints: 1000 rps
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adminLimiter := middleware.NewRateLimiter(1000, 50)
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// Apply different limiters to subrouters
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publicRouter := router.PathPrefix("/public").Subrouter()
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publicRouter.Use(publicLimiter.Middleware)
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apiRouter := router.PathPrefix("/api").Subrouter()
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apiRouter.Use(apiLimiter.Middleware)
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adminRouter := router.PathPrefix("/admin").Subrouter()
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adminRouter.Use(adminLimiter.Middleware)
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}
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```
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### Rate Limit Response
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When rate limited, clients receive:
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```http
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HTTP/1.1 429 Too Many Requests
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Content-Type: text/plain
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```
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### Configuration Examples
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**Tight Rate Limit (Anti-abuse):**
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```go
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// 1 request per second, burst of 3
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rateLimiter := middleware.NewRateLimiter(1, 3)
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```
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**Moderate Rate Limit (Standard API):**
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```go
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// 100 requests per second, burst of 20
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rateLimiter := middleware.NewRateLimiter(100, 20)
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```
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**Generous Rate Limit (Internal Services):**
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```go
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// 1000 requests per second, burst of 100
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rateLimiter := middleware.NewRateLimiter(1000, 100)
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```
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**Time-based Limits:**
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```go
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// 60 requests per minute = 1 request per second
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rateLimiter := middleware.NewRateLimiter(1, 10)
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// 1000 requests per hour ≈ 0.28 requests per second
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rateLimiter := middleware.NewRateLimiter(0.28, 50)
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```
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### Understanding Burst
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The burst parameter allows short bursts above the rate:
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```go
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// Rate: 10 rps, Burst: 5
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// Allows up to 5 requests immediately, then 10/second
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rateLimiter := middleware.NewRateLimiter(10, 5)
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```
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**Bucket fills at rate:** 10 tokens/second
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**Bucket capacity:** 5 tokens
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**Request consumes:** 1 token
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**Example traffic pattern:**
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- T=0s: 5 requests → ✅ All allowed (burst)
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- T=0.1s: 1 request → ❌ Denied (bucket empty)
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- T=0.5s: 1 request → ✅ Allowed (bucket refilled 0.5 tokens)
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- T=1s: 1 request → ✅ Allowed (bucket has ~1 token)
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### Cleanup Behavior
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The rate limiter automatically cleans up inactive limiters every 5 minutes to prevent memory leaks.
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### Performance Characteristics
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- **Memory**: ~100 bytes per active limiter
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- **Throughput**: >1M requests/second
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- **Latency**: <1μs per request
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- **Concurrency**: Lock-free for rate checks
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### Production Deployment
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**With Reverse Proxy:**
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```go
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// Use X-Forwarded-For or X-Real-IP
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keyFunc := func(r *http.Request) string {
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// Check proxy headers first
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if ip := r.Header.Get("X-Forwarded-For"); ip != "" {
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return strings.Split(ip, ",")[0]
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}
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if ip := r.Header.Get("X-Real-IP"); ip != "" {
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return ip
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}
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return r.RemoteAddr
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}
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router.Use(rateLimiter.MiddlewareWithKeyFunc(keyFunc))
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```
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**Environment-based Configuration:**
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```go
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import "os"
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func getRateLimiter() *middleware.RateLimiter {
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rps := getEnvFloat("RATE_LIMIT_RPS", 100)
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burst := getEnvInt("RATE_LIMIT_BURST", 20)
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return middleware.NewRateLimiter(rps, burst)
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}
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```
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### Testing Rate Limits
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```bash
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# Send 10 requests rapidly
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for i in {1..10}; do
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curl -w "Status: %{http_code}\n" http://localhost:8080/api/data
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done
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```
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**Expected output:**
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```
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Status: 200 # Request 1-5 (within burst)
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Status: 200
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Status: 200
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Status: 200
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Status: 200
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Status: 429 # Request 6-10 (rate limited)
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Status: 429
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Status: 429
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Status: 429
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Status: 429
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```
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### Complete Example
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```go
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package main
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import (
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"encoding/json"
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"log"
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"net/http"
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"os"
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"strconv"
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"github.com/bitechdev/ResolveSpec/pkg/middleware"
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"github.com/gorilla/mux"
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)
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func main() {
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// Configuration from environment
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rps, _ := strconv.ParseFloat(os.Getenv("RATE_LIMIT_RPS"), 64)
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if rps == 0 {
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rps = 100 // Default
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}
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burst, _ := strconv.Atoi(os.Getenv("RATE_LIMIT_BURST"))
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if burst == 0 {
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burst = 20 // Default
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}
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// Create rate limiter
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rateLimiter := middleware.NewRateLimiter(rps, burst)
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// Custom key extraction
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keyFunc := func(r *http.Request) string {
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// Try API key first
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if apiKey := r.Header.Get("X-API-Key"); apiKey != "" {
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return "api:" + apiKey
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}
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// Try authenticated user
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if userID := r.Header.Get("X-User-ID"); userID != "" {
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return "user:" + userID
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}
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// Fall back to IP
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if ip := r.Header.Get("X-Forwarded-For"); ip != "" {
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return ip
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}
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return r.RemoteAddr
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}
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// Create router
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router := mux.NewRouter()
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// Apply rate limiting
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router.Use(rateLimiter.MiddlewareWithKeyFunc(keyFunc))
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// Routes
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router.HandleFunc("/api/data", dataHandler)
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router.HandleFunc("/health", healthHandler)
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log.Printf("Starting server with rate limit: %.1f rps, burst: %d", rps, burst)
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log.Fatal(http.ListenAndServe(":8080", router))
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}
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func dataHandler(w http.ResponseWriter, r *http.Request) {
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json.NewEncoder(w).Encode(map[string]string{
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"message": "Data endpoint",
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})
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}
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func healthHandler(w http.ResponseWriter, r *http.Request) {
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w.WriteHeader(http.StatusOK)
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w.Write([]byte("OK"))
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}
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```
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## Best Practices
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1. **Set Appropriate Limits**: Consider your backend capacity
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- Database: Can it handle X queries/second?
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- External APIs: What are their rate limits?
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- Server resources: CPU, memory, connections
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2. **Use Burst Wisely**: Allow legitimate traffic spikes
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- Too low: Reject valid bursts
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- Too high: Allow abuse
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3. **Monitor Rate Limits**: Track how often limits are hit
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```go
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// Log rate limit events
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if rateLimited {
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log.Printf("Rate limited: %s", clientKey)
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}
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```
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4. **Provide Feedback**: Include rate limit headers (future enhancement)
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```http
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X-RateLimit-Limit: 100
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X-RateLimit-Remaining: 95
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X-RateLimit-Reset: 1640000000
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```
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5. **Tiered Limits**: Different limits for different user tiers
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```go
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func getRateLimiter(userTier string) *middleware.RateLimiter {
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switch userTier {
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case "premium":
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return middleware.NewRateLimiter(1000, 100)
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case "standard":
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return middleware.NewRateLimiter(100, 20)
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default:
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return middleware.NewRateLimiter(10, 5)
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}
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}
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```
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```
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