Nginx

Web server configuration, reverse proxy, SSL/TLS, load balancing, caching, and security.

Configuration Structure

# /etc/nginx/nginx.conf — contexts nest: main → events/http → server → location
main context          # worker_processes, error_log, pid
├── events { }        # worker_connections, multi_accept
├── http { }          # upstream, server, mime types, logging
│   ├── server { }    # listen, server_name, ssl
│   │   └── location { }  # request routing
│   └── upstream { }  # backend pools
└── stream { }        # TCP/UDP proxying (mail, databases)

# File layout (Debian/Ubuntu)
/etc/nginx/nginx.conf              # main config
/etc/nginx/sites-available/        # virtual host configs
/etc/nginx/sites-enabled/          # symlinks to available
/etc/nginx/conf.d/                 # additional configs (auto-included)
/etc/nginx/snippets/               # reusable config fragments

Basic Server Block

server {
    listen 80;
    server_name example.com www.example.com;
    root /var/www/myapp;
    index index.html;

    location / {
        try_files $uri $uri/ =404;
    }
}

Reverse Proxy

server {
    listen 80;
    server_name api.example.com;

    location / {
        proxy_pass http://localhost:3000;
        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 X-Forwarded-Proto $scheme;
    }

    # WebSocket upgrade
    location /ws/ {
        proxy_pass http://localhost:3000;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
        proxy_read_timeout 86400s;
    }
}

Load Balancing

upstream backend {
    server 127.0.0.1:3001;          # round-robin (default)
    server 127.0.0.1:3002;
    server 127.0.0.1:3003 backup;   # only when others are down
}

upstream backend_sticky {
    ip_hash;                         # sticky sessions
    server 127.0.0.1:3001 weight=5; # weighted: gets 5x traffic
    server 127.0.0.1:3002 weight=1;
}

upstream backend_least {
    least_conn;                      # fewest active connections
    server 127.0.0.1:3001;
    server 127.0.0.1:3002;
}

server {
    location / {
        proxy_pass http://backend;
        proxy_next_upstream error timeout http_502 http_503;
    }
}

SSL/TLS (HTTPS)

server {
    listen 80;
    server_name example.com;
    return 301 https://$host$request_uri;
}

server {
    listen 443 ssl http2;
    server_name example.com;
    ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;
    ssl_protocols TLSv1.2 TLSv1.3;
    ssl_ciphers ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256;
    ssl_prefer_server_ciphers off;
    ssl_session_cache shared:SSL:10m;
    add_header Strict-Transport-Security "max-age=63072000; includeSubDomains; preload" always;
    ssl_stapling on;
    ssl_stapling_verify on;
    resolver 8.8.8.8 8.8.4.4 valid=300s;

    location / { proxy_pass http://localhost:3000; }
}

# Let's Encrypt with Certbot
sudo certbot --nginx -d example.com -d www.example.com
sudo certbot renew --dry-run
# Auto-renewal: 0 0,12 * * * certbot renew --quiet --post-hook "nginx -s reload"

# Self-signed (dev only)
openssl req -x509 -nodes -days 365 -newkey rsa:2048 \
  -keyout /etc/ssl/private/selfsigned.key \
  -out /etc/ssl/certs/selfsigned.crt -subj "/CN=localhost"

Location Block Matching

# Priority order (first match wins):
# 1. = exact match              location = /health
# 2. ^~ prefix (stops regex)    location ^~ /static/
# 3. ~ regex (case-sensitive)   location ~ \.php$
# 4. ~* regex (case-insensitive) location ~* \.(jpg|png)$
# 5. prefix (longest match)     location /api/

location = /health { return 200 "OK"; add_header Content-Type text/plain; }
location ^~ /static/ { root /var/www; }
location /api/ { proxy_pass http://localhost:3000/; }  # trailing slash strips /api/

location ~* \.(jpg|jpeg|png|gif|ico|css|js|woff2)$ {
    expires 30d;
    add_header Cache-Control "public, immutable";
}

Static File Serving

# root — appends location to path
location /images/ { root /var/www; }       # serves /var/www/images/photo.jpg

# alias — replaces location with path
location /img/ { alias /var/www/images/; } # serves /var/www/images/photo.jpg

# SPA fallback — all routes resolve to index.html
server {
    root /var/www/app/dist;
    index index.html;
    location / { try_files $uri $uri/ /index.html; }
    location /assets/ { expires 1y; add_header Cache-Control "public, immutable"; access_log off; }
    location = /index.html { add_header Cache-Control "no-cache"; }
}

Security Headers

# Add to server or http block
add_header X-Frame-Options "SAMEORIGIN" always;
add_header X-Content-Type-Options "nosniff" always;
add_header X-XSS-Protection "1; mode=block" always;
add_header Referrer-Policy "strict-origin-when-cross-origin" always;
add_header Permissions-Policy "camera=(), microphone=(), geolocation=()" always;
add_header Content-Security-Policy "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:; font-src 'self'" always;
server_tokens off;

Rate Limiting

# Define zones in http block
limit_req_zone $binary_remote_addr zone=api:10m rate=10r/s;
limit_req_zone $binary_remote_addr zone=login:10m rate=1r/s;
limit_conn_zone $binary_remote_addr zone=addr:10m;

server {
    location /api/ {
        limit_req zone=api burst=20 nodelay;
        proxy_pass http://localhost:3000;
    }
    location /auth/login {
        limit_req zone=login burst=5;
        limit_req_status 429;
        proxy_pass http://localhost:3000;
    }
    location /download/ {
        limit_conn addr 5;
        limit_rate 500k;   # throttle bandwidth per connection
    }
}

Proxy Caching

# Define cache zone in http block
proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=app_cache:10m
    max_size=1g inactive=60m use_temp_path=off;

server {
    location /api/ {
        proxy_pass http://backend;
        proxy_cache app_cache;
        proxy_cache_valid 200 10m;
        proxy_cache_valid 404 1m;
        proxy_cache_key $scheme$request_method$host$request_uri;
        proxy_cache_use_stale error timeout updating http_500 http_502;
        add_header X-Cache-Status $upstream_cache_status;
    }
    location /api/private/ {
        proxy_pass http://backend;
        proxy_cache_bypass $http_authorization;
        proxy_no_cache $http_authorization;
    }
}

Compression

# Gzip (in http block)
gzip on;
gzip_vary on;
gzip_proxied any;
gzip_comp_level 6;
gzip_min_length 1000;
gzip_types text/plain text/css application/json application/javascript
    text/xml application/xml image/svg+xml application/wasm;

# Brotli (requires ngx_brotli module)
brotli on;
brotli_comp_level 6;
brotli_types text/plain text/css application/json application/javascript
    text/xml application/xml image/svg+xml;

Redirect and Rewrite Rules

# www to non-www (301)
server { server_name www.example.com; return 301 https://example.com$request_uri; }

# Temporary redirect (302)
location /old-page { return 302 /new-page; }

# Rewrite (internal URL transformation)
rewrite ^/blog/(\d+)$ /articles?id=$1 last;
rewrite ^/legacy/(.*)$ /new/$1 permanent;

Access Control

# IP whitelisting
location /admin/ {
    allow 192.168.1.0/24;
    allow 10.0.0.0/8;
    deny all;
    proxy_pass http://localhost:3000;
}

# Basic auth
location /protected/ {
    auth_basic "Restricted";
    auth_basic_user_file /etc/nginx/.htpasswd;
    proxy_pass http://localhost:3000;
}

sudo apt install apache2-utils && sudo htpasswd -c /etc/nginx/.htpasswd admin

Logging

log_format main '$remote_addr - $remote_user [$time_local] '
    '"$request" $status $body_bytes_sent '
    '"$http_referer" "$http_user_agent" rt=$request_time';

# JSON logging (for log aggregation)
log_format json_log escape=json '{'
    '"time":"$time_iso8601",'
    '"remote_addr":"$remote_addr",'
    '"request":"$request",'
    '"status":$status,'
    '"body_bytes_sent":$body_bytes_sent,'
    '"request_time":$request_time,'
    '"upstream_response_time":"$upstream_response_time"'
    '}';

access_log /var/log/nginx/access.log main;
error_log /var/log/nginx/error.log warn;  # levels: debug info notice warn error crit
location = /health { access_log off; return 200 "OK"; }

Performance Tuning

worker_processes auto;
worker_rlimit_nofile 65535;

events {
    worker_connections 4096;
    multi_accept on;
    use epoll;   # Linux; use kqueue on FreeBSD/macOS
}

http {
    sendfile on;
    tcp_nopush on;
    tcp_nodelay on;
    keepalive_timeout 65;
    keepalive_requests 1000;
    client_max_body_size 50m;
    proxy_buffer_size 128k;
    proxy_buffers 4 256k;
    open_file_cache max=10000 inactive=30s;
    open_file_cache_valid 60s;
}

Docker + Nginx

FROM nginx:alpine
COPY nginx.conf /etc/nginx/conf.d/default.conf
COPY dist/ /usr/share/nginx/html/
EXPOSE 80

# docker-compose.yml — reverse proxy for multiple services
services:
  nginx:
    image: nginx:alpine
    ports: ["80:80", "443:443"]
    volumes:
      - ./nginx.conf:/etc/nginx/nginx.conf:ro
      - ./certs:/etc/nginx/certs:ro
    depends_on: [app, api]
  app:
    build: ./app
    expose: ["3000"]
  api:
    build: ./api
    expose: ["4000"]

Troubleshooting

# 413 Request Entity Too Large → client_max_body_size 50m;
# 502 Bad Gateway → check upstream is running, check error log, increase proxy timeouts
# Permission denied → sudo chown -R www-data:www-data /var/www/
# server_names_hash error → server_names_hash_bucket_size 64;

Common Commands

sudo nginx -t                    # test configuration
sudo nginx -s reload             # reload (no downtime)
sudo systemctl start nginx
sudo systemctl stop nginx
sudo systemctl status nginx
tail -f /var/log/nginx/access.log
tail -f /var/log/nginx/error.log
sudo ln -s /etc/nginx/sites-available/myapp /etc/nginx/sites-enabled/
sudo nginx -t && sudo nginx -s reload
nginx -T                         # dump full resolved config