nginx.conf

# ===== High-Performance Nginx Configuration for 500+ Concurrent Users =====

# Auto-detect available CPU cores
worker_processes auto;

# Maximum number of open files per worker
worker_rlimit_nofile 65535;

# Performance tuning
pcre_jit on;

events {
    # Connections per worker (65535 / worker_processes)
    worker_connections 4096;
    
    # Accept as many connections as possible
    multi_accept on;
    
    # Use epoll for Linux (most efficient)
    use epoll;
}

http {
    # ===== Basic Settings =====
    charset utf-8;
    sendfile on;
    tcp_nopush on;
    tcp_nodelay on;
    
    # Timeouts
    keepalive_timeout 65;
    keepalive_requests 1000;
    send_timeout 30;
    
    # Buffer sizes
    client_body_buffer_size 16k;
    client_header_buffer_size 1k;
    client_max_body_size 10m;
    large_client_header_buffers 4 8k;
    
    # Types
    include /etc/nginx/mime.types;
    default_type application/json;
    
    # ===== Logging =====
    log_format main '$remote_addr - $remote_user [$time_local] "$request" '
                    '$status $body_bytes_sent "$http_referer" '
                    '"$http_user_agent" "$http_x_forwarded_for" '
                    'rt=$request_time uct="$upstream_connect_time" '
                    'uht="$upstream_header_time" urt="$upstream_response_time"';
    
    access_log /var/log/nginx/access.log main buffer=16k flush=5s;
    error_log /var/log/nginx/error.log warn;
    
    # ===== Gzip Compression =====
    gzip on;
    gzip_vary on;
    gzip_proxied any;
    gzip_comp_level 4;
    gzip_min_length 256;
    gzip_buffers 16 8k;
    gzip_http_version 1.1;
    gzip_types
        application/json
        application/javascript
        application/xml
        application/xml+rss
        text/css
        text/javascript
        text/plain
        text/xml;
    
    # ===== Upstream Configuration with Load Balancing =====
    upstream api_gateway {
        # Least connections load balancing (best for varying response times)
        least_conn;
        
        # Connection pooling - keep connections alive to upstreams
        keepalive 32;
        keepalive_requests 1000;
        keepalive_timeout 60s;
        
        # API Gateway instances (can scale with replicas)
        server api-gateway:3000 max_fails=3 fail_timeout=30s;
        # Uncomment when using replicas:
        # server api-gateway-2:3000 max_fails=3 fail_timeout=30s;
        # server api-gateway-3:3000 max_fails=3 fail_timeout=30s;
    }
    
    # Direct service upstreams (for service-specific routing)
    upstream user_service {
        least_conn;
        keepalive 16;
        server user-service:3001 max_fails=3 fail_timeout=30s;
    }
    
    upstream product_service {
        least_conn;
        keepalive 16;
        server product-service:3002 max_fails=3 fail_timeout=30s;
    }
    
    upstream order_service {
        least_conn;
        keepalive 16;
        server order-service:3003 max_fails=3 fail_timeout=30s;
    }
    
    # ===== Proxy Cache =====
    proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=api_cache:10m max_size=100m inactive=60m use_temp_path=off;
    
    # ===== Rate Limiting Zones =====
    # Increased for high-load testing - adjust for production
    limit_req_zone $binary_remote_addr zone=api_limit:10m rate=500r/s;
    limit_req_zone $binary_remote_addr zone=auth_limit:10m rate=50r/s;
    limit_conn_zone $binary_remote_addr zone=conn_limit:10m;
    
    # ===== Main Server Block =====
    server {
        listen 80;
        server_name localhost;
        
        # Connection limit per IP
        limit_conn conn_limit 200;
        
        # ===== Health Check Endpoint =====
        location /nginx-health {
            access_log off;
            return 200 "healthy\n";
            add_header Content-Type text/plain;
        }
        
        # ===== API Gateway Proxy =====
        location / {
            # Rate limiting with burst
            limit_req zone=api_limit burst=50 nodelay;
            
            proxy_pass http://api_gateway;
            
            # HTTP/1.1 for keepalive connections
            proxy_http_version 1.1;
            
            # Headers
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
            proxy_set_header Connection "";
            
            # Timeouts
            proxy_connect_timeout 10s;
            proxy_send_timeout 60s;
            proxy_read_timeout 60s;
            
            # Buffer settings
            proxy_buffering on;
            proxy_buffers 16 16k;
            proxy_buffer_size 16k;
            proxy_busy_buffers_size 32k;
            
            # Error handling
            proxy_next_upstream error timeout http_500 http_502 http_503 http_504;
            proxy_next_upstream_tries 2;
            proxy_next_upstream_timeout 30s;
        }
        
        # ===== Auth Endpoints (Stricter Rate Limiting) =====
        location /api/auth/ {
            limit_req zone=auth_limit burst=5 nodelay;
            
            proxy_pass http://api_gateway;
            proxy_http_version 1.1;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header Connection "";
            
            # Longer timeout for registration (bcrypt)
            proxy_read_timeout 30s;
        }
        
        # ===== Cacheable Endpoints =====
        location /api/products {
            limit_req zone=api_limit burst=100 nodelay;
            
            proxy_pass http://api_gateway;
            proxy_http_version 1.1;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header Connection "";
            
            # Enable caching for GET requests
            proxy_cache api_cache;
            proxy_cache_methods GET HEAD;
            proxy_cache_valid 200 1m;
            proxy_cache_valid 404 30s;
            proxy_cache_key $scheme$request_method$host$request_uri;
            add_header X-Cache-Status $upstream_cache_status;
            
            # Bypass cache for authenticated requests
            proxy_cache_bypass $http_authorization;
            proxy_no_cache $http_authorization;
        }
        
        # ===== Categories (Highly Cacheable) =====
        location /api/categories {
            limit_req zone=api_limit burst=100 nodelay;
            
            proxy_pass http://api_gateway;
            proxy_http_version 1.1;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header Connection "";
            
            # Aggressive caching for categories
            proxy_cache api_cache;
            proxy_cache_methods GET HEAD;
            proxy_cache_valid 200 5m;
            proxy_cache_key $scheme$request_method$host$request_uri;
            add_header X-Cache-Status $upstream_cache_status;
        }
        
        # ===== Health Endpoint =====
        location /health {
            access_log off;
            proxy_pass http://api_gateway;
            proxy_http_version 1.1;
            proxy_set_header Connection "";
        }
        
        # ===== Metrics Endpoint (Prometheus) =====
        location /metrics {
            proxy_pass http://api_gateway;
            proxy_http_version 1.1;
            proxy_set_header Connection "";
        }
    }
    
    # ===== Status Page for Monitoring =====
    server {
        listen 8081;
        server_name localhost;
        
        location /nginx_status {
            stub_status on;
            access_log off;
            allow 127.0.0.1;
            allow 172.16.0.0/12;
            allow 10.0.0.0/8;
            deny all;
        }
    }
}