urlshorten

a urlshortening web service in Go

urlshorten is a simple URL shortening service written in Go. It is based on my webshell framework, and is a simple example of writing a web service that includes templating and authentication.

Setting Up

The setup/setup tool should be used to initialise the database. The database file defaults to data/urlshorten.db. This may be changed in the configuration file, but the file has to be specified on the command line for the setup tool.

The database should be initialised with setup -d /path/to/db/file -c to create the database. The -a flag adds a user to the database, and -r removes the user. The setup program will prompt for the user name, and, where applicable, the password. Note that while the program will create the database file as needed, it will not create intermediary directories.

Finally, you should create any directories needed to store log files in, and ensure the service has permission to write them. By default, the service looks for the directory "logs" in the same directory it was run in.

The Configuration File

Configuration is done with the goconfig package. The configuration file consists of two sections: server and page.

server

This section configures the server. It supports the following options:

• port: set the port the server should listen on. Defaults to 8080.
• host: set the host the host the server should listen on. This is separate from the page option with this name. Defaults to an empty string to listen on all interfaces.
• authenticate: if set to "false", turns off checks for authentication. This is on by default.
• admin_user: set the administrative user; this is used to add new users to the site. The default is not set; no users can be added via the site.
• development: set this to false to disable development features; in development mode, links are set up as host:port. Links in development mode also use the http scheme. If development mode is turned off, links use https and the port is not included in links. Defaults to true.
• dbfile: specify the path to the database file. Defaults to data/urlshorten.db.
• access_log: specify the path to the access log that should be written; if no file is specified it will default to logs/access. The logs are written to access-<date>.log.
• error_log: specifiy the path to the error log that should be written; to the access log.

page

This section controls page templates. Valid options are:

• title: sets the page title. Defaults to urlshorten.go.
• host: the host name to use in links. Defaults to localhost. This affects displayed links to shortcodes only.

Example production configuration file:

[server]
port = 8100
host = 127.0.0.1
development = false
admin_user = flynn

[page]
title = nodality.io
host = nodality.io

This will set up a server that listens on 127.0.0.1:8080 in production mode; pages will have a title of "nodality.io" and links will point to https://nodality.io. The user flynn can add new users via the web interface.

Authentication

If you have enabled authentication, a username and password will be required to shorten any urls. Enabling authentication also enables the /add and /change routes. However, you will need to set up an initial user using the command line tool as noted above.

Running The Service

It is recommended to run the service behind a proxy; in nginx, you could do this with

upstream goweb {
        server 127.0.0.1:8080;
} 

server {
	listen 80;
	server_name example.net;
	rewrite ^(.*) https://$host$1 permanent;
}

server {
	listen 443 ;
	server_name example.net

	access_log /var/log/nginx/example_access.log;
	error_log /var/log/nginx/example_error.log;
	location / {
  		proxy_set_header  X-Real-IP  $remote_addr;
		proxy_pass http://goweb;
	}

        ssl on;
	ssl_certificate /etc/ssl/certs/example.pem;
	ssl_certificate_key /etc/ssl/private/example.key;

	ssl_session_timeout 5m;

	ssl_protocols TLSv1;
	ssl_ciphers ALL:!ADH:!EXPORT56:RC4+RSA:+HIGH:!MEDIUM:!LOW:+SSLv3:+EXP;
	ssl_prefer_server_ciphers on;

}

In this case, nginx handles all the TLS aspects and proxies incoming requests.

Then, navigate to https://example.net/. Your passwords may be changed with https://example.net/change. You can add a new user at https://example.net/add.