URL shortener
The job of a URL shortener is to take a long URL (e.g. "https://www.cockroachlabs.com/docs/stable/build-a-go-app-with-cockroachdb.html") and turn it into something shorter (e.g. "https://bit.ly/2QLUQIu").
A simple URL shortener with no special rules is very simple and consists of 2 endpoints:
- One to generate a short version of a URL given a long version of a URL.
- One to handle a call to the short version of a URL and redirect the user to the long (original) version of the URL.
Create a simple URL shortening API with the following endpoints:
POST /
A POST endpoint that accepts a JSON body describing the URL to shorten. Your URL shortener should generate a short version of the URL and keep track of the mapping between short and long URLs. For example:
$ curl -X POST 'localhost:8080' \ -H 'Content-Type: application/json' \ -d '{ "long": "https://www.cockroachlabs.com/docs/stable/build-a-go-app-with-cockroachdb.html" }'
Should returning something similar to:
http://localhost:8080/9eXmFnuj
GET /:short
A GET endpoint that accepts a short version of the URL in the URL path and redirects the user to the original URL. For example:
$ curl -L http://localhost:3000/9eXmFnuj
Should redirect the user to the original URL:
<!DOCTYPE html> <html lang="en"> ...
Rules:
- Store the short -> long mappings in any way you like. In-memory is fine.
- There are no auth requirements. Your API can be completely open.
Crystal
<lang ruby>require "kemal"
CHARS = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".chars entries = Hash(String, String).new
post "/" do |env|
short = Random::Secure.random_bytes(8).map{|b| CHARS[b % CHARS.size]}.join entries[short] = env.params.json["long"].as(String) "http://localhost:3000/#{short}"
end
get "/:short" do |env|
if long = entries[env.params.url["short"]]? env.redirect long else env.response.status_code = 404 end
end
error 404 do
"invalid short url"
end
Kemal.run</lang>
Delphi
Highly inspired in #Go <lang Delphi> program URLShortenerServer;
{$APPTYPE CONSOLE}
uses
System.SysUtils, System.Classes, System.Json, IdHTTPServer, IdContext, IdCustomHTTPServer, IdGlobal, Inifiles;
type
TUrlShortener = class private Db: TInifile; Server: TIdHTTPServer; function GenerateKey(size: integer): string; procedure Get(Path: string; AResponseInfo: TIdHTTPResponseInfo); procedure Post(Url: string; AReqBody: TJSONValue; AResponseInfo: TIdHTTPResponseInfo); function PostBody(Data: TStream): TJSONValue; function StoreLongUrl(Url: string): string; public procedure DoGet(AContext: TIdContext; ARequestInfo: TIdHTTPRequestInfo; AResponseInfo: TIdHTTPResponseInfo); procedure StartListening; constructor Create; destructor Destroy; override; end;
const
Host = 'localhost:8080'; CODE_CHARS = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'; SHORTENER_SEASON = 'URL_SHORTER';
{ Manager }
function TUrlShortener.GenerateKey(size: integer): string; var
le, i: integer;
begin
SetLength(Result, size); le := Length(CODE_CHARS)-1; for i := 1 to size do Result[i] := CODE_CHARS[Random(le)+1];
end;
procedure TUrlShortener.StartListening; begin
Server.Active := true;
end;
function TUrlShortener.StoreLongUrl(Url: string): string; begin
repeat Result := GenerateKey(8); until not Db.ValueExists(SHORTENER_SEASON, Result); Db.WriteString(SHORTENER_SEASON, Result, Url); Db.UpdateFile;
end;
procedure TUrlShortener.Get(Path: string; AResponseInfo: TIdHTTPResponseInfo); var
longUrl: string;
begin
if Db.ValueExists(SHORTENER_SEASON, Path) then begin longUrl := Db.ReadString(SHORTENER_SEASON, Path, ); AResponseInfo.ResponseNo := 302; AResponseInfo.Redirect(longUrl); end else begin AResponseInfo.ResponseNo := 404; writeln(format('No such shortened url: http://%s/%s', [host, Path])); end;
end;
procedure TUrlShortener.Post(Url: string; AReqBody: TJSONValue; AResponseInfo:
TIdHTTPResponseInfo);
var
longUrl, shortUrl: string;
begin
if Assigned(AReqBody) then begin longUrl := AReqBody.GetValue<string>('long'); shortUrl := StoreLongUrl(longUrl); AResponseInfo.ResponseNo := 200; AResponseInfo.ContentText := Host + '/' + shortUrl; end else AResponseInfo.ResponseNo := 422;
end;
function TUrlShortener.PostBody(Data: TStream): TJSONValue; var
body: string;
begin
Result := nil; if assigned(Data) then begin Data.Position := 0; body := ReadStringFromStream(Data);
result := TJSONObject.Create; try result := TJSONObject.ParseJSONValue(body); except on E: Exception do FreeAndNil(Result); end; end;
end;
constructor TUrlShortener.Create; begin
Db := TInifile.Create(ChangeFileExt(ParamStr(0), '.db')); Server := TIdHTTPServer.Create(nil); Server.DefaultPort := 8080; Server.OnCommandGet := DoGet;
end;
destructor TUrlShortener.Destroy; begin
Server.Active := false; Server.Free; Db.Free; inherited;
end;
procedure TUrlShortener.DoGet(AContext: TIdContext; ARequestInfo:
TIdHTTPRequestInfo; AResponseInfo: TIdHTTPResponseInfo);
var
Path: string;
begin
// Default ResponseNo AResponseInfo.ResponseNo := 404;
Path := ARequestInfo.URI.Replace('/', , []);
case ARequestInfo.CommandType of hcGET: Get(Path, AResponseInfo); hcPOST: Post(Path, PostBody(ARequestInfo.PostStream), AResponseInfo); else Writeln('Unsupprted method: ', ARequestInfo.Command); end;
end;
var
Server: TIdHTTPServer; Manager: TUrlShortener;
begin
Manager := TUrlShortener.Create; Manager.StartListening;
Writeln('Running on ', host); Writeln('Press ENTER to exit'); readln;
Manager.Free;
end.</lang>
- Output:
Running on localhost:8080 Press ENTER to exit
Go
<lang go>// shortener.go package main
import (
"encoding/json" "fmt" "io/ioutil" "log" "math/rand" "net/http" "time"
)
const (
chars = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ" host = "localhost:8000"
)
type database map[string]string
type shortener struct {
Long string `json:"long"`
}
func (db database) ServeHTTP(w http.ResponseWriter, req *http.Request) {
switch req.Method { case http.MethodPost: // "POST" body, err := ioutil.ReadAll(req.Body) if err != nil { w.WriteHeader(http.StatusBadRequest) // 400 return } var sh shortener err = json.Unmarshal(body, &sh) if err != nil { w.WriteHeader(http.StatusUnprocessableEntity) // 422 return } short := generateKey(8) db[short] = sh.Long fmt.Fprintf(w, "The shortened URL: http://%s/%s\n", host, short) case http.MethodGet: // "GET" path := req.URL.Path[1:] if v, ok := db[path]; ok { http.Redirect(w, req, v, http.StatusFound) // 302 } else { w.WriteHeader(http.StatusNotFound) // 404 fmt.Fprintf(w, "No such shortened url: http://%s/%s\n", host, path) } default: w.WriteHeader(http.StatusNotFound) // 404 fmt.Fprintf(w, "Unsupprted method: %s\n", req.Method) }
}
func generateKey(size int) string {
key := make([]byte, size) le := len(chars) for i := 0; i < size; i++ { key[i] = chars[rand.Intn(le)] } return string(key)
}
func main() {
rand.Seed(time.Now().UnixNano()) db := make(database) log.Fatal(http.ListenAndServe(host, db))
}</lang>
- Output:
Sample output (abbreviated) including building and starting the server from Ubuntu 18.04 terminal and entering a valid and then an invalid shortened URL:
$ go build shortener.go $ ./shortener & $ curl -X POST 'localhost:8000' \ > -H 'Content-Type: application/json' \ > -d '{ > "long": "https://www.cockroachlabs.com/docs/stable/build-a-go-app-with-cockroachdb.html" > }' The shortened URL: http://localhost:8000/3DOPwhRu $ curl -L http://localhost:8000/3DOPwhRu <!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <meta name="viewport" content="width=device-width, initial-scale=1"> <meta name="description" content="Learn how to use CockroachDB from a simple Go application with the Go pq driver."> .... </html> $ curl -L http://localhost:8000/3DOPwhRv No such shortened url: http://localhost:8000/3DOPwhRv
JavaScript
<lang JavaScript>#!/usr/bin/env node
var mapping = new Map();
// assure num. above 36 ^ 9 var base = 101559956668416; // 36 ^ (10 -> length of ID) var ceil = 3656158440062976; // these are calculated as: // l = desired length // 198 > l > 1 // -> above 198 ends up as Infinity // -> below 1 ends up as 0, as one would except (pun intended) // base = 36 ^ (l - 1) // ceil = 36 ^ l
require('http').createServer((req, res) => { if(req.url === '/') { // only accept POST requests as JSON to / if(req.method !== 'POST' || req.headers['content-type'] !== 'application/json') { // 400 Bad Request res.writeHead(400); return res.end(); }
var random = (Math.random() * (ceil - base) + base).toString(36); req.on('data', chunk => { // trusting input json to be valid, e.g., '{"long":"https://www.example.com/"}' var body = JSON.parse(chunk.toString()); mapping.set(random.substring(0, 10), body.long); // substr gets the integer part });
// 201 Created res.writeHead(201); return res.end('http://localhost:8080/' + random.substring(0, 10)); }
var url = mapping.get(req.url.substring(1)); if(url) { // 302 Found res.writeHead(302, { 'Location': url }); return res.end(); }
// 404 Not Found res.writeHead(404); res.end(); }).listen(8080);</lang>
- Output:
$ curl -X POST http://localhost:8080/ -H "Content-Type: application/json" --data "{\"long\":\"https://www.example.com\"}" http://localhost:8080/bcg4x4lla8 $
http://localhost:8080/bcg4x4lla8 then redirects to www.example.com
Julia
Assumes an SQLite database containing a table called LONGNAMESHORTNAME (consisting of two string columns) already exists. <lang julia>using Base64, HTTP, JSON2, Sockets, SQLite, SHA
function processpost(req::HTTP.Request, urilen=8)
json = JSON2.read(String(HTTP.payload(req))) if haskey(json, :long) longname = json.long encoded, shortname = [UInt8(c) for c in base64encode(sha256(longname))], "" for i in 0:length(encoded)-1 shortname = String(circshift(encoded, i)[1:urilen]) result = SQLite.Query(dbhandle, "SELECT LONG FROM LONGNAMESHORTNAME WHERE SHORT = \"" * shortname * "\";") if isempty(result) SQLite.Query(dbhandle, "INSERT INTO LONGNAMESHORTNAME VALUES ('" * longname * "', '" * shortname * "')") return HTTP.Response(200, JSON2.write( "$shortname is short name for $longname.")) end end end HTTP.Response(400, JSON2.write("Bad request. Please POST JSON as { long : longname }"))
end
function processget(req::HTTP.Request)
shortname = split(req.target, r"[^\w\d\+\\]+")[end] result = SQLite.Query(dbhandle, "SELECT LONG FROM LONGNAMESHORTNAME WHERE SHORT = \'" * shortname * "\' ;") responsebody = isempty(result) ?
"<!DOCTYPE html><html><head></head><body>
Not Found
</body></html>" :
"<!DOCTYPE html><html><head></head><body>\n<meta http-equiv=\"refresh\"" * "content = \"0; url = " * first(result).LONG * " /></body></html>" return HTTP.Response(200, responsebody)
end
function run_web_server(server, portnum)
router = HTTP.Router() HTTP.@register(router, "POST", "", processpost) HTTP.@register(router, "GET", "/*", processget) HTTP.serve(router, server, portnum)
end
const dbhandle = SQLite.DB("longshort.db") const serveraddress = Sockets.localhost const localport = 3000 run_web_server(serveraddress, localport) </lang>
Phix
-- -- demo\rosetta\URL_shortener.exw -- ============================== -- -- Uses a routine originally written for a code minifier, so were you to run this -- for a long time, you'd get 52 one-character short urls, ie a..z and A..Z, then -- 3,224 (=52*62) two-character short urls, as 2nd char on can also be 0..9, then -- 199,888 (=52*62*62) three-character short urls, and so on. The dictionary used -- is not [yet] saved/reloaded between runs. No attempt is made to re-produce the -- same short url if the same long url is passed in twice. Nothing remotely like -- any form of error handling, as per the usual "for clarity". -- -- Windows only for now (should be straightforward to get it working on linux) -- (routines in builtins\sockets.e that be windows-only.) -- -- See sample session output (in a separate terminal) for usage instructions. -- without js include builtins\sockets.e include builtins\json.e constant MAX_QUEUE = 100, ESCAPE = #1B, shortened = substitute(""" HTTP/1.1 200 OK Content-Type: text/plain; charset=utf-8 Content-Length: %d The shortened URL: http://localhost:8080/%s ""","\n","\r\n"), redirect = substitute(""" HTTP/1.1 302 Found Content-Type: text/html; charset=UTF-8 Content-Length: %d Location: %s <a href="%s">Found</a>. ""","\n","\r\n"), not_found = substitute(""" HTTP/1.1 404 Not Found Content-Type: text/plain; charset=utf-8 Content-Length: %d No such shortened url: http://localhost:8080/%s ""","\n","\r\n") integer shurl = new_dict() string response, lnk, url constant alphabet = tagset('z','a')&tagset('Z','A')&tagset('9','0') function short_id(integer n) string res = "" integer base = 52 -- (first char azAZ) while n do res &= alphabet[remainder(n-1,base)+1] n = floor((n-1)/base) base = 62 -- (subsequent chars azAZ09) end while return res end function puts(1,"server started, open http://localhost:8080/ in browser or curl, press Esc or Q to quit\n") atom sock = socket(AF_INET,SOCK_STREAM,NULL), pSockAddr = sockaddr_in(AF_INET, "", 8080) if bind(sock, pSockAddr)=SOCKET_ERROR then crash("bind (%v)",{get_socket_error()}) end if if listen(sock,MAX_QUEUE)=SOCKET_ERROR then crash("listen (%v)",{get_socket_error()}) end if while not find(get_key(),{ESCAPE,'q','Q'}) do {integer code} = select({sock},{},{},250000) if code=SOCKET_ERROR then crash("select (%v)",{get_socket_error()}) end if if code>0 then -- (not timeout) atom peer = accept(sock), ip = getsockaddr(peer) {integer len, string request} = recv(peer) printf(1,"Client IP: %s\n%s\n",{ip_to_string(ip),request}) if length(request)>5 and request[1..5]="POST " then string json = request[find('{',request)..$] object json_data = parse_json(json) url = extract_json_field(json_data,"long") lnk = short_id(dict_size(shurl)+1) setd(lnk,url,shurl) response = sprintf(shortened,{length(lnk)+45,lnk}) elsif length(request)>4 and request[1..4]="GET " then lnk = request[6..find(' ',request,6)-1] integer node = getd_index(lnk,shurl) if node then url = getd_by_index(node,shurl) response = sprintf(redirect,{length(url)+23,url,url}) else response = sprintf(not_found,{length(lnk)+49,lnk}) end if else ?9/0 -- uh? end if integer bytes_sent = send(peer,response) printf(1,"%d bytes successfully sent\n",bytes_sent) shutdown(peer, SD_SEND) -- tell curl it's over peer = closesocket(peer) -- (as does this) end if end while sock = closesocket(sock) WSACleanup()
- Output:
Sample session output:
C:\Program Files (x86)\Phix>curl http://localhost:8080/X No such shortened url: http://localhost:8000/X C:\Program Files (x86)\Phix>curl -X POST "localhost:8080" -H "Content-Type: application/json" -d "{\"long\":\"https://www.cockroachlabs.com/docs/stable/build-a-go-app-with-cockroachdb.html\"}" The shortened URL: http://localhost:8000/a C:\Program Files (x86)\Phix>curl http://localhost:8080/a <a href="https://www.cockroachlabs.com/docs/stable/build-a-go-app-with-cockroachdb.html">Found</a>.
Of course if you paste http://localhost:8080/a into a browser (with URL_shortener.exw still running!) it goes to the right place.
Meanwhile, in a separate terminal (with * replaced by $ to avoid comment issues) we get:
server started, open http://localhost:8080/ in browser or curl, press Esc or Q to quit Client IP: 127.0.0.1 GET /a HTTP/1.1 Host: localhost:8080 User-Agent: curl/7.55.1 Accept: $/$ 137 bytes successfully sent Client IP: 127.0.0.1 POST / HTTP/1.1 Host: localhost:8080 User-Agent: curl/7.55.1 Accept: $/$ Content-Type: application/json Content-Length: 89 {"long":"https://www.cockroachlabs.com/docs/stable/build-a-go-app-with-cockroachdb.html"} 126 bytes successfully sent Client IP: 127.0.0.1 GET /a HTTP/1.1 Host: localhost:8080 User-Agent: curl/7.55.1 Accept: $/$ 276 bytes successfully sent
PicoLisp
<lang PicoLisp>(load "@lib/http.l") (allowed NIL "!short" u) (pool "urls.db" (6)) (de short (R)
(ifn *Post (redirect (fetch NIL (format R))) (let K (count) (dbSync) (store NIL K (get 'u 'http)) (commit 'upd) (respond (pack "http://127.0.0.1:8080/?" K "\n")) ) ) )
(server 8080 "!short")</lang>
- Output:
$ nohup pil url-short.l + $ curl -F 'u=https://reddit.com' 127.0.0.1:8080 http://127.0.0.1:8080/?0 $ curl -F 'u=https://picolisp.com' 127.0.0.1:8080 http://127.0.0.1:8080/?1 $ curl -v http://127.0.0.1:8080/?1 * Trying 127.0.0.1:8080... * Connected to 127.0.0.1 (127.0.0.1) port 8080 (#0) > GET /?1 HTTP/1.1 > Host: 127.0.0.1:8080 > User-Agent: curl/7.69.1 > Accept: */* > * Mark bundle as not supporting multiuse < HTTP/1.1 303 See Other < Server: PicoLisp < Location: https://picolisp.com < Content-Type: text/html < Content-Length: 89 < <HTML> <HEAD><TITLE>303 See Other</TITLE></HEAD> <BODY><H1>See Other</H1></BODY> </HTML> * Connection #0 to host 127.0.0.1 left intact $
Python
Flask
<lang python> """A URL shortener using Flask. Requires Python >=3.5."""
import sqlite3 import string import random
from http import HTTPStatus
from flask import Flask from flask import Blueprint from flask import abort from flask import current_app from flask import g from flask import jsonify from flask import redirect from flask import request from flask import url_for
CHARS = frozenset(string.ascii_letters + string.digits)
MIN_URL_SIZE = 8
RANDOM_ATTEMPTS = 3
def create_app(*, db=None, server_name=None) -> Flask:
app = Flask(__name__) app.config.from_mapping( DATABASE=db or "shorten.sqlite", SERVER_NAME=server_name, )
with app.app_context(): init_db()
app.teardown_appcontext(close_db) app.register_blueprint(shortener)
return app
def get_db():
if "db" not in g: g.db = sqlite3.connect(current_app.config["DATABASE"]) g.db.row_factory = sqlite3.Row
return g.db
def close_db(_):
db = g.pop("db", None)
if db is not None: db.close()
def init_db():
db = get_db()
with db: db.execute( "CREATE TABLE IF NOT EXISTS shorten (" "url TEXT PRIMARY KEY, " "short TEXT NOT NULL UNIQUE ON CONFLICT FAIL)" )
shortener = Blueprint("shorten", "short")
def random_short(size=MIN_URL_SIZE):
"""Return a random URL-safe string `size` characters in length.""" return "".join(random.sample(CHARS, size))
@shortener.errorhandler(HTTPStatus.NOT_FOUND)
def short_url_not_found(_):
return "short url not found", HTTPStatus.NOT_FOUND
@shortener.route("/<path:key>", methods=("GET",))
def short(key):
db = get_db()
cursor = db.execute("SELECT url FROM shorten WHERE short = ?", (key,)) row = cursor.fetchone()
if row is None: abort(HTTPStatus.NOT_FOUND)
# NOTE: Your might want to change this to HTTPStatus.MOVED_PERMANENTLY return redirect(row["url"], code=HTTPStatus.FOUND)
class URLExistsError(Exception):
"""Exception raised when we try to insert a URL that is already in the database."""
class ShortCollisionError(Exception):
"""Exception raised when a short URL is already in use."""
def _insert_short(long_url, short):
"""Helper function that checks for database integrity errors explicitly before inserting a new URL.""" db = get_db()
if ( db.execute("SELECT * FROM shorten WHERE url = ?", (long_url,)).fetchone() is not None ): raise URLExistsError(long_url)
if ( db.execute("SELECT * FROM shorten WHERE short = ?", (short,)).fetchone() is not None ): raise ShortCollisionError(short)
with db: db.execute("INSERT INTO shorten VALUES (?, ?)", (long_url, short))
def make_short(long_url):
"""Generate a new short URL for the given long URL.""" size = MIN_URL_SIZE attempts = 1 short = random_short(size=size)
while True: try: _insert_short(long_url, short) except ShortCollisionError: # Increase the short size if we keep getting collisions. if not attempts % RANDOM_ATTEMPTS: size += 1
attempts += 1 short = random_short(size=size) else: break
return short
@shortener.route("/", methods=("POST",))
def shorten():
data = request.get_json()
if data is None: abort(HTTPStatus.BAD_REQUEST)
long_url = data.get("long")
if long_url is None: abort(HTTPStatus.BAD_REQUEST)
db = get_db()
# Does this URL already have a short? cursor = db.execute("SELECT short FROM shorten WHERE url = ?", (long_url,)) row = cursor.fetchone()
if row is not None: short_url = url_for("shorten.short", _external=True, key=row["short"]) status_code = HTTPStatus.OK else: short_url = url_for("shorten.short", _external=True, key=make_short(long_url)) status_code = HTTPStatus.CREATED
mimetype = request.accept_mimetypes.best_match( matches=["text/plain", "application/json"], default="text/plain" )
if mimetype == "application/json": return jsonify(long=long_url, short=short_url), status_code else: return short_url, status_code
if __name__ == "__main__":
# Start the development server app = create_app() app.env = "development" app.run(debug=True)
</lang>
Raku
(formerly Perl 6)
As there is no requirement to obfuscate the shortened urls, I elected to just use a simple base 36 incremental counter starting at "0" to "shorten" the urls.
Sets up a micro web service on the local computer at port 10000. Run the service, then access it with any web browser at address localhost:10000 . Any saved urls will be displayed with their shortened id. Enter a web address in the text field to assign a shortened id. Append that id to the web address to automatically be redirected to that url. The url of this page is entered as id 0, so the address: " localhost:10000/0 " will redirect to here, to this page.
The next saved address would be accessible at localhost:10000/1 . And so on.
Saves the shortened urls in a local json file called urls.json so saved urls will be available from session to session. No provisions to edit or delete a saved url. If you want to edit the saved urls, edit the urls.json file directly with some third party editor then restart the service.
There is NO security or authentication on this minimal app. Not recommended to run this as-is on a public facing server. It would not be too difficult to add appropriate security, but it isn't a requirement of this task. Very minimal error checking and recovery.
<lang perl6># Persistent URL storage use JSON::Fast;
my $urlfile = './urls.json'.IO; my %urls = ($urlfile.e and $urlfile.f and $urlfile.s) ??
( $urlfile.slurp.&from-json ) !! ( index => 1, url => { 0 => 'http://rosettacode.org/wiki/URL_shortener#Raku' } );
$urlfile.spurt(%urls.&to-json);
- Setup parameters
my $host = 'localhost'; my $port = 10000;
- Micro HTTP service
use Cro::HTTP::Router; use Cro::HTTP::Server;
my $application = route {
post -> 'add_url' { redirect :see-other, '/'; request-body -> (:$url) { %urls<url>{ %urls<index>.base(36) } = $url; ++%urls<index>; $urlfile.spurt(%urls.&to-json); } }
get -> { content 'text/html', qq:to/END/; <form action="http://$host:$port/add_url" method="post"> URL to add:
<input type="text" name="url">
<input type="submit" value="Submit"></form>
Saved URLs:
{ %urls<url>.sort( +(*.key.parse-base(36)) ).join: '
' }
END }
get -> $short { if my $link = %urls<url>{$short} { redirect :permanent, $link } else { not-found } }
}
my Cro::Service $shorten = Cro::HTTP::Server.new:
:$host, :$port, :$application;
$shorten.start;
react whenever signal(SIGINT) { $shorten.stop; exit; } </lang>