Serve - Easily dockerize Single-Page Javascript Apps

A fast Go fileserver with a focus on versatility and security. Can be used stand-alone or behind a reverse proxy / load balancer. The main intention is to serve SPA assets from within Docker containers.

serve was created out of the need to have a reliable light-weight shipping method for SPA apps in Docker. The alternative - mounting assets from data-only Docker containers into a webserver container - is hard to manage because it relies on a special Docker feature that copies files from an exported volume to the host. Updating such a data-only container requires to remove it manually, remove the volume manually and restarting the webserver to bind-mount the new volume from the new container.

Works similar to Nginx try_files directive with some extra features and configuration options.

Features

• HTTP/1.1 and HTTP/2.0 support
• TLS server support
• HTTP file server with auto mime-type detection
• serves multi-language index.html based on Accept-Language request header
• template replacement from ENV variables for safe secrets injection
• custom HTTP headers
• custom HTTP cache settings
• configurable access logs
• CSP report logging

Main Server Configuration

Configuration works via a JSON config file (default location is /etc/serve/config.json or config.json in CWD) and environment variables prefixed SV_ (ENV takes precedence over config file settings).

Examples below contain defaults values.

{
  "server": {
    // interface to bind to, env SV_SERVER_ADDR
    "addr": "0.0.0.0",
    // port number to bind to, env SV_SERVER_PORT
    "port": 8000,
    // protocol schema, either http or https, env SV_SERVER_SCHEME
    "scheme": "http",
    // filesystem root directory, env SV_SERVER_ROOT
    "root": "/var/www",
    // base URL (optional), env SV_SERVER_BASE
    "base": "",
    // app index file name, env SV_SERVER_INDEX
    "index": "index.html"
  }
}

TLS Configuration

TLS is optional and will be enabled when you choose https as server scheme.

{
  "server": {
    // server name for SNI (optional), env SV_SERVER_NAME
    "name": "",
    // TLS minimum version (e.g. 0 for TLSv1.0 to 3 for TLSv1.3), SV_SERVER_TLS_MIN_VERSION
    "tls_min_version": 3,
    // TLS maximum version (e.g. 0 for TLSv1.0 to 3 for TLSv1.3), SV_SERVER_TLS_MAX_VERSION
    "tls_max_version": 3,
    // TLS CA as PEM (multi-line strings will be concatenated), SV_SERVER_TLS_CA
    "tls_ca": [],
    // TLS CA file in PEM format, SV_SERVER_TLS_CA_FILE
    "tls_ca_file": "",
    // TLS Server Cert in PEM format (multi-line strings will be concatenated), SV_SERVER_TLS_CERT
    "tls_cert": [],
    // TLS Server Cert file in PEM format, SV_SERVER_TLS_CERT_FILE
    "tls_cert_file": "",
    // TLS Server Key in PEM format (multi-line strings will be concatenated), SV_SERVER_TLS_KEY
    "tls_key": [],
    // TLS Server Key file in PEM format, SV_SERVER_TLS_KEY_FILE
    "tls_key_file": ""
  }
}

Config and Secrets Injection

When serving files, serve can scan for placeholders (<[..]>) and replace them with the contents of environment variables on the fly. This way you can inject URLs, API keys, tokens, identifiers, and any kind of configuration settings into your Javascript and HTML files. That allows you to deploy the same docker images across integration testing, staging and production.

This feature is enabled by default. Don't use the same characters for start and end delimiters.

  "template": {
    // enables or disables injection, env SV_TEMPLATE_ENABLE
    "enable": true,
    // template start delimiter, env SV_TEMPLATE_LEFT
    "left": "<[",
    // template end delimiter, env SV_TEMPLATE_RIGHT
    "right": "]>",
    // Go regexp to select files for injection, env SV_TEMPLATE_MATCH
    "match": "\\.(html|js)$",
    // max file size (helps prevent memory pressure), ebv SV_TEMPLATE_MAXSIZE
    "maxsize": 16777216
  }

Multi-Language Index Support

serve can serve different index.html files based on the contents of the Accept-Language request header by trying different filenames with language used as prefix. Remember that you can change the name of the served index file in the server section or via SV_SERVER_INDEX.

Example for filename composition for default index.html:

Accept-Language: en-US,en;q=0.5

# first tried filename
en-us-index.html

# second tried filename
en-index.html

# generic fallback
index.html

Controlling HTTP Caching

To control how serve returns HTTP cache headers you can specify multiple cache rules. This feature is enabled by default and will allow public caching of all files for 30 seconds.

  "cache": {
    // enables or disabled cache headers, env SV_CACHE_ENABLE
    "enable": true,
    // set default cache lifetime, env SV_CACHE_EXIRES
    "expires": "30s",
    // set default cache policy, env SV_CACHE_CONTROL
    "control": "public",
    // define multiple rules to overwrite the default policy (config file only, NO env!)
    "rules": [{
      // specify a regexp to match files, i.e. for all index.html files
      "regexp": "\\.*index.html$",
      // send cache-control `max-age=0, no-cache, no-store, must-revalidate`
      "nocache": true,
      // do not send cache headers at all
      "ignore": true
    },{
      // specify a regexp to match files, i.e. all asset types
      "regexp": "\\.(js|css|png|jpg|jpeg|svg|ico|woff|ttf|eot|otf)$",
      // set a very long expiry time (e.g. 10 years)
      "expires": "87600h",
      // set an infinite expiry policy
      "control": "public, max-age=31536000, immutable",
    }]
  }

Setting Custom HTTP Headers

Additional response headers may be added under the headers key as key/values. They will be added to all served files.

{
  "headers": {
    "key": "value"
  }
}

How to build

You need Git and Go installed on your machine. No special dependencies required.

git clone https://github.com/echa/serve.git
cd serve && go build

How to run

go run .

License

The MIT License (MIT) Copyright (c) 2019 KIDTSUNAMI.