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Introduction to the CloudStackAPISebastien Goasguen@sebgoa

Outline• Documentation• Clients• Exploration• Integration port• Signing requests• REST or not REST

Documentationhttp://cloudstack.apache.org/docs/api/apidocs-4.0.0/TOC_Root_Admin.htmlhttp://cloudstack.apache.org/docs/en-US/Apache_CloudStack/4.0.1-incubating/html/API_Developers_Guide/index.html

Clients• 15 clients andcounting… on Github• Java, Python, Perl,Ruby, C#, php, Clojure

Exploration• Use a debugger console• E.g Firebug• As you navigate the UI,check the http calls thatare being made• Identify the methods• Identify the parameterspassed to each call

HTTPbased• API calls made via HTTP(s)• Pass name of the call as command• Pass list of key/value pairs as arguments tothe call• GET method• Response can be XML or JSON• Query API that is RESTlikehttp://gehrcke.de/2009/06/aws-about-api/

Integration Port• Unauthenticated call– Dangerous– Don’t open it all– Certainly don’t open it to the public internet• Set the port on the UI

$Using theintegration porthttp://localhost:8096/client/api?command=listUsers&response=jsoncurl 'http://localhost:8096/client/api?command=listUsers&response=json'{ "listusersresponse" : { "count":3 ,"user" : [ {"id":"7ed6d5da-93b2-4545-a502-23d20b48ef2a","username":"admin","firstname":"admin","lastname":"cloud","created":"2012-07-05T12:18:27-0700","state":"enabled","account":"admin","accounttype":1,"domainid":"8a111e58-e155-4482-93ce-84efff3c7c77","domain":"ROOT","apikey":"plgWJfZK4gyS3mOMTVmjUVg-X-jlWlnfaUJ9GAbBbf9EdM-kAYMmAiLqzzq1ElZLYq_u38zCm0bewzGUdP66mg”…http://localhost:8096/client/api?command=listUserscurl http://localhost:8096/client/api?command=listUsers<?xml version="1.0" encoding="ISO-8859-1"?><listusersresponse cloud-stack-version="3.0.3.2012-07-04T06:31:57Z"><count>3</count><user><id>7ed6d5da-93b2-4545-a502-23d20b48ef2a</id><username>admin</username><firstname>admin</firstname><lastname>cloud</lastname><created>2012-07-05T12:18:27-0700</created><state>enabled</state><account>admin</account><accounttype>1</accounttype><domainid>8a111e58-e155-4482-93ce-84efff3c7c77</domainid><domain>ROOT</domain><apikey>plgWJfZK4gyS3mOMTVmjUVg-X-jlWlnfaUJ9GAbBbf9EdM-kAYMmAiLqzzq1ElZLYq_u38zCm0bewzGUdP66mg…http://www.shapeblue.com/2012/05/10/using-the-api-for-advanced-network-management/$

Authenticated calls• Using http(s)• API endpoint for the cloud– http://localhost:8080/client/api?• Command key to pass the name of the call• Key/value pairs for the arguments• API key of the user making the call• Signature for authorization

API Keys• Generate API keys for the user that will accessthe cloud

Creating the signature• Form the request url: list of key=valuepairs joined by & and encoded for httptransport• Compute the signature:– lower case values, replace + with %20– generate the hmac using sha1 hash function– Base64 encode the digest– Encode for http transport• Form the entire request adding the signature:&signature=

$Example>>> request{'apikey': 'plgWJfZK4gyS3mOMTVmjUVg-X-jlWlnfaUJ9GAbBbf9EdM-kAYMmAiLqzzq1ElZLYq_u38zCm0bewzGUdP66mg', 'command': 'listUsers','response': 'json'}>>>request_url="&".join(["=".join([r,urllib.quote_plus(request[r])]) for r in request.keys()])>>>sig_url="&".join(["=".join([r.lower(),urllib.quote_plus(request[r]).lower()]) for r in sorted(request.iterkeys())])>>>sig=urllib.quote_plus(base64.encodestring(hmac.new(secretkey,sig_url,hashlib.sha1).digest()).strip())>>> req=url+request_url+'&signature='+sig>>> res=urllib2.urlopen(req)>>> res.read()$

REST• REST stands for Representational StateTransfer• Architectural style to design web servicesintroduced by Roy Fielding (former ASF chair)• Premise:– HTTP protocol is enough to create web servicesand change the state of web resources– HTTP methods can be used to change the state– Eases web services design compared to SOAPhttp://en.wikipedia.org/wiki/Roy_Fieldinghttp://en.wikipedia.org/wiki/Representational_State_Transfer

REST• REST style web services couple beimplemented with other protocol than http• But http provides all that is neededhttp://en.wikipedia.org/wiki/Representational_State_Transfer

REST API• The CloudStack API is a query API• It is RESTlike but not RESTfull• Example:listUsers() a GET vs GETupdateUser() a GET vs PATCHcreateUser() a GET vs POSTdeleteUser() a GET vs DELETEhttp://gehrcke.de/2009/06/aws-about-api/http://publish.luisrei.com/articles/flaskrest.html

Exercise• Build a REST interface to CloudStack• Use Flask a Lightweight Python webframeworkhttp://flask.pocoo.orghttp://publish.luisrei.com/articles/flaskrest.html

Exercisefrom flask import Flaskapp = Flask(__name__)@app.route("/")def hello():return "Hello World!"if __name__ == "__main__":app.run(debug=True)Flask allows you to define web routes andfunctions that get executed when these routesare called.

$Exercise@app.route('/login', methods=['GET', 'POST'])def login():if request.method == 'POST':do_the_login()else:show_the_login_form()curl -X DELETEhttp://localhost:5000/user/b3b60a8dfdf6f-4ce6-a6f9-6194907457a5{ "deleteuserresponse" : { "success" : "true"} }https://github.com/runseb/cloudstack-flaskhttp://buildacloud.org/blog/253-to-rest-or-not-to-rest.html$