user nginx;
worker_processes auto;
error_log /var/log/nginx/error.log warn;
pid /var/run/nginx.pid;

events {
    worker_connections 2048;
    multi_accept on;
}

http {
    include /etc/nginx/mime.types;
    default_type application/octet-stream;

    # `request_id` is generated here when the client did not supply one and is
    # forwarded to the API, which echoes it back. One id ties the browser's
    # network tab, this access log and the application log together.
    log_format json_combined escape=json
        '{'
        '"time":"$time_iso8601",'
        '"request_id":"$http_x_request_id",'
        '"remote_addr":"$remote_addr",'
        '"method":"$request_method",'
        '"uri":"$request_uri",'
        '"status":$status,'
        '"bytes":$body_bytes_sent,'
        '"duration":$request_time,'
        '"upstream_time":"$upstream_response_time",'
        '"referer":"$http_referer",'
        '"user_agent":"$http_user_agent"'
        '}';

    access_log /var/log/nginx/access.log json_combined;

    sendfile on;
    tcp_nopush on;
    tcp_nodelay on;
    keepalive_timeout 65;
    server_tokens off;

    client_max_body_size 25m;
    client_body_timeout 30s;

    gzip on;
    gzip_vary on;
    gzip_min_length 1024;
    gzip_proxied any;
    gzip_types
        application/javascript
        application/json
        application/xml
        image/svg+xml
        text/css
        text/plain
        text/xml;

    # Defence in depth. The API rate-limits per actor; this is a blunt
    # per-IP ceiling that protects the app tier from ever seeing a flood.
    limit_req_zone $binary_remote_addr zone=api_limit:10m rate=30r/s;
    limit_req_zone $binary_remote_addr zone=web_limit:10m rate=60r/s;
    limit_req_status 429;

    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;
    proxy_set_header X-Request-Id $request_id;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";

    include /etc/nginx/conf.d/*.conf;
}