Tuesday, December 10, 2013

Performance testing on REST API

    RESTful API has great promises in simplifying the development on web/smartphone apps and handling a larger number of clients.  How can we effectively test servers that support RESTful APIs?

   To load-test RESTful service, we need to be able to generate HTTP requests with methods like "PUT", "DELETE" etc.  You are right, they may not be the familiar ones like GET, POST,  but on NetGend platform, it's easy to emulate just about any HTTP method:

 http.method = "PUT";  
 http.method = "DELETE".  

    Note that by default, the http method is "GET" on NetGend platform,  if you need HTTP POST method,  you can simply do it by
 http.method = "POST";  
 //or just specify there is http POST data.  
 http.POSTData = "name=john&city=houston";  

    When you generate HTTP Body in JSON format (say for HTTP Post message),  you can either use a template or use the function combineHttpParam.
 http.POSTData = q|{ "name": "john", "city": "Houston", "age": "23"}|;  
 person.name = "john";  
 person.city  = "Houston";  
 person.age  = 23;  
 http.POSTData = combineHttpParam(person);  

    Did you notice that the you don't have to escape the double-quotes in the template?   On the other test platforms you may have to write { \"name\": \"john\", \"city\": \"Houston\", \"age\": \"23\"} ?  If you think escaping is a pain, you are not alone!  Now you understand why I think it's a pleasure to do it on the NetGend platform.

    The URL path for RESTful request may look like the following:
/rest/8af909ffefa9/getDiston.json/10001/20002/mile, it can be generated in two ways.

 //method 1, by variable substitution 
 //assume you have the variables defined  
 //method 2, by join an array
 a[0] = apiKey;  
 a[1] = "getDistance.json";  
 a[2] = zip1;  
 a[3] = zip2;  
 a[4] = "mile"; //can have other unit  
 apiMsg = join(a, "/");  
 action(http, "http://www.example.com/rest/${apiMsg}");  

    HTTP responses for RESTful are increasingly in JSON format.  Parsing JSON message is pretty simple on NetGend platform and has been covered many times in the previous blogs.  The following is an example of JSON message from a site that implements a "todo" list.

 [ {"id": 1,  
     "text": "reserve lunch"  
    }, {"id": 2,  
     "text": "fix mower"  
    }, {"id": 3,  
     "text": "buy grocery"  

     Let's put all these together and try to test the RESTful site for "todo" list by implementing the following sequence.
  • Get a list of existing "todos"
  • randomly delete one of them
  • add a new one 
  • update a random "todo"

 action(http, "http://www.example.com/todos/"); 

 //delete a random one 
 resp = fromJson(http.replyBody);  
 id = randNumber(1, getSize(resp) );  
 http.POSTData = q|{"id": ${id}}|;  
 http.method = "DELETE";  
 action(http, "http://www.example.com/todos");  

 //add a new one  
 http.POSTData = q|{"text": "talk to insurance agent"}|;  
 action(http, "http://www.example.com/todos");  

 action(http, "http://www.example.com/todos/");  
 resp = fromJson(http.replyBody);  
 id = randNumber(1, getSize(resp) );  
 http.POSTData = q|{ "text": "updated content!", "id": ${id}}|;  
 http.method = "PUT";  
 action(http, "http://www.example.com/todos");  

    There are obviously more test scenarios,  I am sure they will feel just as pleasant like this one!

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