API Server: Extension and Operating Patterns

1
import "github.com/sony/gobreaker"
2
3
var (
4
    recipeStoreBreaker *gobreaker.CircuitBreaker
5
)
6
7
func init() {
8
    settings := gobreaker.Settings{
9
        Name:        "RecipeStore",
10
        MaxRequests: 3,  // Half-open state allows 3 requests
11
        Interval:    60 * time.Second,  // Reset counts every 60s
12
        Timeout:     30 * time.Second,  // Stay open for 30s
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        ReadyToTrip: func(counts gobreaker.Counts) bool {
14
            failureRatio := float64(counts.TotalFailures) / float64(counts.Requests)
15
            return counts.Requests >= 10 && failureRatio >= 0.6
16
        },
17
        OnStateChange: func(name string, from gobreaker.State, to gobreaker.State) {
18
            log.Info("Circuit breaker state changed",
19
                "name", name,
20
                "from", from,
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                "to", to,
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            )
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        },
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    }
25
    
26
    recipeStoreBreaker = gobreaker.NewCircuitBreaker(settings)
27
}
28
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func handleRecipe(w http.ResponseWriter, r *http.Request) {
30
    result, err := recipeStoreBreaker.Execute(func() (interface{}, error) {
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        return buildRecipe(r.Context(), params)
32
    })
33
    
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    if err != nil {
35
        if errors.Is(err, gobreaker.ErrOpenState) {
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            http.Error(w, "Service temporarily unavailable", http.StatusServiceUnavailable)
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            return
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        }
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        http.Error(w, err.Error(), http.StatusInternalServerError)
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        return
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    }
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    recipe := result.(*recipe.Recipe)
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    json.NewEncoder(w).Encode(recipe)
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}

1
import "golang.org/x/sync/semaphore"
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3
var (
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    // Separate semaphores for different endpoints
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    recipeSem   = semaphore.NewWeighted(100)  // 100 concurrent recipe requests
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    snapshotSem = semaphore.NewWeighted(10)   // 10 concurrent snapshot requests
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)
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func handleRecipeWithBulkhead(w http.ResponseWriter, r *http.Request) {
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    // Acquire from recipe bulkhead
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    if !recipeSem.TryAcquire(1) {
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        http.Error(w, "Too many requests", http.StatusTooManyRequests)
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        return
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    }
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    defer recipeSem.Release(1)
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    // Process request
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    handleRecipe(w, r)
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}
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func handleSnapshotWithBulkhead(w http.ResponseWriter, r *http.Request) {
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    // Acquire from snapshot bulkhead (more expensive operation)
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    if !snapshotSem.TryAcquire(1) {
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        http.Error(w, "Too many requests", http.StatusTooManyRequests)
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        return
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    }
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    defer snapshotSem.Release(1)
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    handleSnapshot(w, r)
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}

1
import "github.com/cenkalti/backoff/v4"
2
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func fetchRecipeWithRetry(ctx context.Context, key string) (*recipe.Recipe, error) {
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    var r *recipe.Recipe
5
    
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    operation := func() error {
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        var err error
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        r, err = recipeStore.Get(ctx, key)
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        // Don't retry on 404
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        if errors.Is(err, ErrNotFound) {
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            return backoff.Permanent(err)
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        }
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        return err
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    }
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    // Exponential backoff: 100ms, 200ms, 400ms, 800ms, 1.6s, 3.2s
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    bo := backoff.NewExponentialBackOff()
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    bo.InitialInterval = 100 * time.Millisecond
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    bo.MaxInterval = 5 * time.Second
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    bo.MaxElapsedTime = 30 * time.Second
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    err := backoff.Retry(operation, backoff.WithContext(bo, ctx))
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    return r, err
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}

1
var (
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    recipeCacheTTL = 1 * time.Hour
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    recipeCache    = sync.Map{}
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)
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type cachedRecipe struct {
7
    recipe    *recipe.Recipe
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    timestamp time.Time
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}
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func handleRecipeWithFallback(w http.ResponseWriter, r *http.Request) {
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    key := buildCacheKey(r)
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    // Try primary source
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    recipe, err := buildRecipe(r.Context(), params)
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    if err == nil {
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        // Cache successful response
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        recipeCache.Store(key, cachedRecipe{
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            recipe:    recipe,
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            timestamp: time.Now(),
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        })
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        json.NewEncoder(w).Encode(recipe)
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        return
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    }
26
    
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    // Primary failed - try cache
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    if cached, ok := recipeCache.Load(key); ok {
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        cr := cached.(cachedRecipe)
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        age := time.Since(cr.timestamp)
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        log.Warn("Serving stale recipe",
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            "key", key,
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            "age", age,
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            "error", err,
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        )
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        w.Header().Set("X-Cache", "stale")
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        w.Header().Set("X-Cache-Age", age.String())
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        json.NewEncoder(w).Encode(cr.recipe)
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        return
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    }
43
    
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    // No cache available
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    http.Error(w, "Service unavailable", http.StatusServiceUnavailable)
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}

1
var httpClient = &http.Client{
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    Transport: &http.Transport{
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        MaxIdleConns:        100,
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        MaxIdleConnsPerHost: 10,
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        IdleConnTimeout:     90 * time.Second,
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        DisableCompression:  false,
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        ForceAttemptHTTP2:   true,
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    },
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    Timeout: 10 * time.Second,
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}
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// Reuse client for all outbound requests
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resp, err := httpClient.Get("https://recipe-store.example.com/recipes")

1
import "github.com/patrickmn/go-cache"
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3
var (
4
    responseCache = cache.New(5*time.Minute, 10*time.Minute)
5
)
6
7
func handleRecipeWithCache(w http.ResponseWriter, r *http.Request) {
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    key := buildCacheKey(r)
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    // Check cache
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    if cached, found := responseCache.Get(key); found {
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        w.Header().Set("X-Cache", "hit")
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        w.Header().Set("Content-Type", "application/json")
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        w.Write(cached.([]byte))
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        return
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    }
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    // Cache miss - build recipe
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    recipe, err := buildRecipe(r.Context(), params)
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    if err != nil {
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        http.Error(w, err.Error(), http.StatusInternalServerError)
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        return
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    }
24
    
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    // Serialize and cache
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    data, err := json.Marshal(recipe)
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    if err != nil {
28
        http.Error(w, err.Error(), http.StatusInternalServerError)
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        return
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    }
31
    responseCache.Set(key, data, cache.DefaultExpiration)
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    w.Header().Set("X-Cache", "miss")
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    w.Header().Set("Content-Type", "application/json")
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    w.Write(data)
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}

1
import "golang.org/x/sync/singleflight"
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var requestGroup singleflight.Group
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func handleRecipeWithCoalescing(w http.ResponseWriter, r *http.Request) {
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    key := buildCacheKey(r)
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    // Deduplicate requests with same key
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    result, err, shared := requestGroup.Do(key, func() (interface{}, error) {
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        return buildRecipe(r.Context(), params)
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    })
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    if shared {
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        w.Header().Set("X-Request-Coalesced", "true")
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    }
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    if err != nil {
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        http.Error(w, err.Error(), http.StatusInternalServerError)
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        return
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    }
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    json.NewEncoder(w).Encode(result)
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}

1
import "golang.org/x/time/rate"
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type ipRateLimiter struct {
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    limiters map[string]*rate.Limiter
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    mu       sync.RWMutex
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    rate     rate.Limit
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    burst    int
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}
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func newIPRateLimiter(r rate.Limit, b int) *ipRateLimiter {
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    return &ipRateLimiter{
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        limiters: make(map[string]*rate.Limiter),
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        rate:     r,
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        burst:    b,
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    }
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}
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func (i *ipRateLimiter) getLimiter(ip string) *rate.Limiter {
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    i.mu.RLock()
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    limiter, exists := i.limiters[ip]
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    i.mu.RUnlock()
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    if !exists {
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        i.mu.Lock()
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        limiter = rate.NewLimiter(i.rate, i.burst)
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        i.limiters[ip] = limiter
27
        
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        // Illustrative cleanup: clears the entire map past a threshold.
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        // Production implementations should use LRU or TTL eviction
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        // (e.g., github.com/hashicorp/golang-lru) so in-flight limiters
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        // are preserved and a request-burst cliff is avoided.
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        if len(i.limiters) > 10000 {
33
            i.limiters = make(map[string]*rate.Limiter)
34
        }
35
        i.mu.Unlock()
36
    }
37
    
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    return limiter
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}
40
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func (i *ipRateLimiter) middleware(next http.Handler) http.Handler {
42
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
43
        ip := getClientIP(r)
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        limiter := i.getLimiter(ip)
45
        
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        if !limiter.Allow() {
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            http.Error(w, "Rate limit exceeded", http.StatusTooManyRequests)
48
            return
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        }
50
        
51
        next.ServeHTTP(w, r)
52
    })
53
}
54
55
func getClientIP(r *http.Request) string {
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    // Check X-Forwarded-For header (behind proxy)
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    xff := r.Header.Get("X-Forwarded-For")
58
    if xff != "" {
59
        ips := strings.Split(xff, ",")
60
        return strings.TrimSpace(ips[0])
61
    }
62
    
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    // Fall back to RemoteAddr
64
    ip, _, err := net.SplitHostPort(r.RemoteAddr)
65
    if err != nil {
66
        // RemoteAddr might not include a port (e.g., some test setups);
67
        // returning RemoteAddr keeps a unique key per peer and avoids
68
        // collapsing every unparseable address into one rate-limit bucket.
69
        return r.RemoteAddr
70
    }
71
    return ip
72
}

1
import "github.com/go-playground/validator/v10"
2
3
var validate = validator.New()
4
5
type RecipeRequest struct {
6
    OS       string `validate:"required,oneof=ubuntu rhel cos"`
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    OSVersion string `validate:"omitempty,semver"`
8
    GPU      string `validate:"required,oneof=h100 gb200 b200 a100 l40 rtx-pro-6000"`
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    Service  string `validate:"omitempty,oneof=eks gke aks oke kind lke"`
10
}
11
12
func handleRecipe(w http.ResponseWriter, r *http.Request) {
13
    req := RecipeRequest{
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        OS:       r.URL.Query().Get("os"),
15
        OSVersion: r.URL.Query().Get("osv"),
16
        GPU:      r.URL.Query().Get("gpu"),
17
        Service:  r.URL.Query().Get("service"),
18
    }
19
    
20
    if err := validate.Struct(req); err != nil {
21
        validationErrors := err.(validator.ValidationErrors)
22
        http.Error(w, validationErrors.Error(), http.StatusBadRequest)
23
        return
24
    }
25
    
26
    // Proceed with validated input
27
}

1
func securityHeadersMiddleware(next http.Handler) http.Handler {
2
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
3
        // HSTS
4
        w.Header().Set("Strict-Transport-Security",
5
            "max-age=31536000; includeSubDomains; preload")
6
        
7
        // Prevent MIME sniffing
8
        w.Header().Set("X-Content-Type-Options", "nosniff")
9
        
10
        // Prevent clickjacking
11
        w.Header().Set("X-Frame-Options", "DENY")
12
        
13
        // XSS protection
14
        w.Header().Set("X-XSS-Protection", "1; mode=block")
15
        
16
        // CSP
17
        w.Header().Set("Content-Security-Policy",
18
            "default-src 'none'; script-src 'self'; connect-src 'self'; img-src 'self'; style-src 'self';")
19
        
20
        // Referrer policy
21
        w.Header().Set("Referrer-Policy", "strict-origin-when-cross-origin")
22
        
23
        next.ServeHTTP(w, r)
24
    })
25
}

1
import "github.com/prometheus/client_golang/prometheus"
2
3
var (
4
    recipeBuildDuration = prometheus.NewHistogramVec(
5
        prometheus.HistogramOpts{
6
            Name:    "aicr_recipe_build_duration_seconds",
7
            Help:    "Time to build recipe",
8
            Buckets: prometheus.ExponentialBuckets(0.001, 2, 12), // 1ms to 4s
9
        },
10
        []string{"os", "gpu", "service"},
11
    )
12
    
13
    recipeCacheHits = prometheus.NewCounterVec(
14
        prometheus.CounterOpts{
15
            Name: "aicr_recipe_cache_hits_total",
16
            Help: "Number of recipe cache hits",
17
        },
18
        []string{"cache_type"},
19
    )
20
    
21
    activeConnections = prometheus.NewGauge(
22
        prometheus.GaugeOpts{
23
            Name: "aicr_active_connections",
24
            Help: "Number of active HTTP connections",
25
        },
26
    )
27
)
28
29
func init() {
30
    prometheus.MustRegister(
31
        recipeBuildDuration,
32
        recipeCacheHits,
33
        activeConnections,
34
    )
35
}
36
37
func handleRecipe(w http.ResponseWriter, r *http.Request) {
38
    start := time.Now()
39
    defer func() {
40
        duration := time.Since(start).Seconds()
41
        recipeBuildDuration.WithLabelValues(
42
            params.OS,
43
            params.GPU,
44
            params.Service,
45
        ).Observe(duration)
46
    }()
47
    
48
    // Check cache
49
    if cached, found := cache.Get(key); found {
50
        recipeCacheHits.WithLabelValues("memory").Inc()
51
        // ...
52
    }
53
    
54
    // Build recipe
55
    // ...
56
}

1
import "log/slog"
2
3
func handleRecipe(w http.ResponseWriter, r *http.Request) {
4
    // Create logger with request context
5
    logger := slog.With(
6
        "request_id", r.Header.Get("X-Request-ID"),
7
        "remote_addr", r.RemoteAddr,
8
        "user_agent", r.UserAgent(),
9
    )
10
    
11
    logger.Info("Handling recipe request",
12
        "os", params.OS,
13
        "gpu", params.GPU,
14
    )
15
    
16
    recipe, err := buildRecipe(r.Context(), params)
17
    if err != nil {
18
        logger.Error("Failed to build recipe",
19
            "error", err,
20
            "params", params,
21
        )
22
        http.Error(w, err.Error(), http.StatusInternalServerError)
23
        return
24
    }
25
    
26
    logger.Info("Recipe built successfully",
27
        "measurement_count", len(recipe.Measurements),
28
        "duration_ms", time.Since(start).Milliseconds(),
29
    )
30
    
31
    json.NewEncoder(w).Encode(recipe)
32
}

1
import (
2
    "go.opentelemetry.io/otel"
3
    "go.opentelemetry.io/otel/attribute"
4
    "go.opentelemetry.io/otel/codes"
5
    "go.opentelemetry.io/otel/trace"
6
)
7
8
func handleRecipe(w http.ResponseWriter, r *http.Request) {
9
    ctx := r.Context()
10
    tracer := otel.Tracer("aicrd")
11
    
12
    ctx, span := tracer.Start(ctx, "handleRecipe",
13
        trace.WithAttributes(
14
            attribute.String("os", params.OS),
15
            attribute.String("gpu", params.GPU),
16
        ),
17
    )
18
    defer span.End()
19
    
20
    // Propagate context to child operations
21
    recipe, err := buildRecipeWithTrace(ctx, params)
22
    if err != nil {
23
        span.RecordError(err)
24
        span.SetStatus(codes.Error, err.Error())
25
        http.Error(w, err.Error(), http.StatusInternalServerError)
26
        return
27
    }
28
    
29
    span.SetAttributes(
30
        attribute.Int("measurement_count", len(recipe.Measurements)),
31
    )
32
    
33
    json.NewEncoder(w).Encode(recipe)
34
}
35
36
func buildRecipeWithTrace(ctx context.Context, params Params) (*recipe.Recipe, error) {
37
    tracer := otel.Tracer("aicrd")
38
    ctx, span := tracer.Start(ctx, "buildRecipe")
39
    defer span.End()
40
    
41
    // Build recipe with traced context
42
    return builder.Build(ctx, params)
43
}