How to Deploy NGINX as an API Gateway

api_backends.conf

upstream warehouse_inventory {
    zone inventory_service 64k;
    server 10.0.0.1:80;
    server 10.0.0.2:80;
    server 10.0.0.3:80;
}

upstream warehouse_pricing {
    zone pricing_service 64k;
    server 10.0.0.7:80;
    server 10.0.0.8:80;
    server 10.0.0.9:80;
}

# vim: syntax=nginx

api_gateway.conf

log_format api_main '$remote_addr - $remote_user [$time_local] "$request" $status $body_bytes_sent "$http_referer" "$http_user_agent" "$http_x_forwarded_for" "$api_name"';

include api_backends.conf;
include api_keys.conf;

server {
    set $api_name -; # Start with an undefined API name, each API will update this value
    access_log /var/log/nginx/api_access.log api_main; # Each API may also log to a separate file

    listen 443 ssl;
    server_name api.example.com;

    # TLS config
    ssl_certificate      /etc/ssl/certs/api.example.com.crt;
    ssl_certificate_key  /etc/ssl/private/api.example.com.key;
    ssl_session_cache    shared:SSL:10m;
    ssl_session_timeout  5m;
    ssl_ciphers          HIGH:!aNULL:!MD5;
    ssl_protocols        TLSv1.1 TLSv1.2;

    # API definitions, one per file
    include api_conf.d/*.conf;

    # Error responses
    error_page 404 = @400;         # Invalid paths are treated as bad requests
    proxy_intercept_errors on;     # Do not send backend errors to the client
    include api_json_errors.conf;  # API client friendly JSON error responses
    default_type application/json; # If no content-type then assume JSON
}

# vim: syntax=nginx

api_json_errors.conf

error_page 400 = @400;
location @400 { return 400 '{"status":400,"message":"Bad request"}\n'; }

error_page 401 = @401;
location @401 { return 401 '{"status":401,"message":"Unauthorized"}\n'; }

error_page 403 = @403;
location @403 { return 403 '{"status":403,"message":"Forbidden"}\n'; }

error_page 404 = @404;
location @404 { return 404 '{"status":404,"message":"Resource not found"}\n'; }

error_page 405 = @405;
location @405 { return 405 '{"status":405,"message":"Method not allowed"}\n'; }

error_page 408 = @408;
location @408 { return 408 '{"status":408,"message":"Request timeout"}\n'; }

error_page 413 = @413;
location @413 { return 413 '{"status":413,"message":"Payload too large"}\n'; }

error_page 414 = @414;
location @414 { return 414 '{"status":414,"message":"Request URI too large"}\n'; }

error_page 415 = @415;
location @415 { return 415 '{"status":415,"message":"Unsupported media type"}\n'; }

error_page 426 = @426;
location @426 { return 426 '{"status":426,"message":"HTTP request was sent to HTTPS port"}\n'; }

error_page 429 = @429;
location @429 { return 429 '{"status":429,"message":"API rate limit exceeded"}\n'; }

error_page 495 = @495;
location @495 { return 495 '{"status":495,"message":"Client certificate authentication error"}\n'; }

error_page 496 = @496;
location @496 { return 496 '{"status":496,"message":"Client certificate not presented"}\n'; }

error_page 497 = @497;
location @497 { return 497 '{"status":497,"message":"HTTP request was sent to mutual TLS port"}\n'; }

error_page 500 = @500;
location @500 { return 500 '{"status":500,"message":"Server error"}\n'; }

error_page 501 = @501;
location @501 { return 501 '{"status":501,"message":"Not implemented"}\n'; }

error_page 502 = @502;
location @502 { return 502 '{"status":502,"message":"Bad gateway"}\n'; }

# vim: syntax=nginx

api_keys.conf

map $http_apikey $api_client_name {
    default "";

    "7B5zIqmRGXmrJTFmKa99vcit" "client_one";
    "QzVV6y1EmQFbbxOfRCwyJs35" "client_two";
    "mGcjH8Fv6U9y3BVF9H3Ypb9T" "client_six";
}

# vim: syntax=nginx

nginx.conf

user  nginx;
worker_processes  auto;

error_log  /var/log/nginx/error.log notice;
pid        /var/run/nginx.pid;

load_module /etc/nginx/modules/ngx_http_js_module.so;

events {
    worker_connections  1024;
}

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

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

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

    sendfile        on;
    #tcp_nopush     on;

    keepalive_timeout  65;

    include /etc/nginx/api_gateway.conf; # All API gateway configuration
    include /etc/nginx/conf.d/*.conf;    # Regular web traffic
}

swagger2nginx.sh

#!/usr/bin/env bash
#
# swagger2nginx.sh (c) NGINX, Inc. [v0.3 03-Jul-2018] Liam Crilly <[email protected]>
#
# Requires shyaml for YAML processing: https://github.com/0k/shyaml

if [ $# -lt 1 ]; then
    echo "### USAGE: `basename $0` [options] swagger_file.yaml"
    echo "### Options:"
    echo "### -b | --basepath <basePath>       # Override Swagger basePath"
    echo "### -l | --location                  # Create policy location (requires -u)"
    echo "### -n | --api-name <API name>       # Override Swagger title"
    echo "### -p | --prefix <prefix path>      # Apply prefix to basePath"
    echo "### -u | --upstream <upstream name>  # Specify upstream group"
    exit 1
fi

which shyaml
if [ $? -ne 0 ]; then
    echo "### `basename $0` ERROR: shyaml not found, see https://github.com/0k/shyaml"
    exit 1
fi

API_NAME=""
DO_LOCATION=0
BASEPATH=""
PREFIX_PATH=""
UPSTREAM=""
while [ $# -gt 1 ]; do
    case "$1" in
        "-b" | "--basepath")
            BASEPATH=$2
            shift; shift
            ;;
        "-l" | "--location")
            DO_LOCATION=1
            shift
            ;;
        "-n" | "--api-name")
            API_NAME=$2
            shift; shift
            ;;
        "-p" | "--prefix")
            PREFIX_PATH=$2
            shift; shift
            ;;
        "-u" | "--upstream")
            UPSTREAM=$2
            shift; shift
            ;;
         *)
            echo "### `basename $0` ERROR: Invalid command line option ($1)"
            exit 1
            ;;
    esac
done

if [ $DO_LOCATION -eq 1 ] && [ "$UPSTREAM" == "" ]; then
    echo "### `basename $0` ERROR: Policy location requires upstream --upstream name"
    exit 1
fi

if [ ! -f $1 ]; then
    echo "### `basename $0` ERROR: Cannot open $1"
    exit 1
fi

if [ "$API_NAME" == "" ]; then
    # Convert title to NGINX-friendly API name
    API_NAME=`shyaml get-value info.title < $1 | tr '[:space:]' '_' | tr -cd '[:alnum:]_-' 2> /dev/null`
    if [ "$API_NAME" == "" ]; then
        echo "### `basename $0` ERROR: Swagger file has missing/invalid title for API name"
        exit 1
    fi
fi

if [ "$BASEPATH" == "" ]; then
    BASEPATH=`shyaml get-value basePath < $1 2> /dev/null`
    if [ "$BASEPATH" == "" ]; then
        echo "### `basename $0` ERROR: No basePath found in Swagger"
        exit 1
    fi
fi
BASEPATH=$PREFIX_PATH$BASEPATH

for SWAGGER_PATH in `shyaml keys paths < $1`; do
    # Convert path templates to regular expressions
    URI=`echo $SWAGGER_PATH | sed -e "s/\({.*}\)/\[\^\/\]\*/g"`

    if [ "$SWAGGER_PATH" == "$URI" ]; then
        echo "location = $BASEPATH$URI {"    # Exact match when no path templates
    else
        echo "location ~ ^$BASEPATH$URI\$ {" # Regex match
    fi

    METHODS=`shyaml keys paths.$SWAGGER_PATH < $1 | grep -v parameters | tr '\n' ' '`
    if [ "$METHODS" != "" ]; then
        echo "    limit_except $METHODS{ deny all; }"
        echo "    error_page 403 = @405;"
    fi

    if [ "$UPSTREAM" != "" ]; then
        echo "    set \$upstream $UPSTREAM;"
    fi

    echo "    rewrite ^ /_$API_NAME last;"
    echo "}"
done

if [ $DO_LOCATION -eq 1 ]; then
    echo ""
    echo "location = /_$API_NAME {"
    echo "    proxy_pass http://\$upstream\$request_uri;"
    echo "}"
fi

warehouse_api_apikeys.conf

# API definition
#
location /api/warehouse/pricing {
    limit_except GET POST {}
    set $upstream pricing_service;
    rewrite ^ /_warehouse last;
}
location /api/warehouse/inventory {
    limit_except GET {}
    set $upstream inventory_service;
    rewrite ^(.*)$ /_warehouse$1 last;
}

# Policy section
#
location = /_warehouse {
    internal;
    set $api_name "Warehouse";  

    if ($http_apikey = "") {
        return 401; # Unauthorized (please authenticate)
    }
    if ($api_client_name = "") {
        return 403; # Forbidden (invalid API key)
    }

    proxy_pass http://$upstream$request_uri;
}

# vim: syntax=nginx

warehouse_api_precise.conf

# API definition (precise)
#
location = /api/warehouse/inventory { # Complete inventory
    set $upstream inventory_service;
    rewrite ^ /_warehouse last;
}
location ~ ^/api/warehouse/inventory/shelf/[^/]*$ { # Shelf inventory
    set $upstream inventory_service;
    rewrite ^ /_warehouse last;
}
location ~ ^/api/warehouse/inventory/shelf/[^/]*/box/[^/]*$ { # Box on shelf
    set $upstream inventory_service;
    rewrite ^ /_warehouse last;
}
location ~ ^/api/warehouse/pricing/[^/]*$ { # Price for specific item
    set $upstream pricing_service;
    rewrite ^ /_warehouse last;
}

# Policy section
#
location = /_warehouse {
    internal;
    set $api_name warehouse_api;

    # Policy configuration here (authentication, rate limiting, logging, more...)

    proxy_pass http://$upstream$request_uri;
}

# vim: syntax=nginx

warehouse_api_rewrites.conf

# Rewrite rules
#
rewrite ^/api/warehouse/inventory/item/price/(.*)  /api/warehouse/pricing/$1;

# API definition
#
location /api/warehouse/inventory {
    set $upstream inventory_service;
    rewrite ^(.*)$ /_warehouse$1 last;
}
location /api/warehouse/pricing {
    set $upstream pricing_service;
    rewrite ^(.*) /_warehouse$1 last;
}

# Policy section
#
location /_warehouse {
    internal;
    set $api_name "Warehouse";

    # Policy configuration here (authentication, rate limiting, logging, more...)

    rewrite ^/_warehouse/(.*)$ /$1 break; # Remove /_warehouse prefix
    proxy_pass http://$upstream;          # Proxy the rewritten URI
}

# vim: syntax=nginx

warehouse_api_simple.conf

# API definition
#
location /api/warehouse/inventory {
    set $upstream warehouse_inventory;
    rewrite ^ /_warehouse last;
}
location /api/warehouse/pricing {
    set $upstream warehouse_pricing;
    rewrite ^ /_warehouse last;
}

# Policy section
#
location = /_warehouse {
    internal;
    set $api_name "Warehouse";

    # Policy configuration here (authentication, rate limiting, logging, more...)

    proxy_pass http://$upstream$request_uri;
}

# vim: syntax=nginx