Isolate Single Service

During deployment and debugging it can be helpful to run a single application or service or handle a sub-set of requests on a local machine in debug mode. Using MockServer it is easy to selectively forward requests to a local process running in debug mode, all other request can be forwarded to the real services for example running in a QA or UAT environment.

For example a single page application may load static resources such as HTML, CSS and JavaScript from a web server and also make AJAX calls to one or more separate services, as follows:

Single Page Application

To isolate a single AJAX service, for development or debugging, the MockServer can selectively forward specific requests to a local instance of the service:

Isolating Single Service

One of the simplest ways to do this is using Node.js. In the example below all requests matching path "/rest.*" (i.e. starting with /rest) will go to the local machine on port 8080 whereas all other requests will go to a remote machine (i.e. a load balancer or remote server) on ip 192.168.50.10 and port 443.

First create a package.json file as follows:

{
 "name": "mockserver_as_reverse_proxy",
 "version": "1.0.0",
 "main": "server.js",
 "dependencies": {
 "mockserver-node": "5.14.0",
 "mockserver-client": "5.14.0"
 }
}<

Then create the server.js file that starts MockServer and sets up the forwarding rules as different expectations, as follows:

var mockserver = require('mockserver-node');
var mockServerClient = require('mockserver-client').mockServerClient;
var HTTP_PORT = 1080;
mockserver
 .start_mockserver({
 serverPort: HTTP_PORT
 })
 .then(function () {
 // forward backend REST API request to local machine
 mockServerClient("localhost", HTTP_PORT)
 .mockAnyResponse({
 "httpRequest": {
 "path": "/rest.*"
 },
 "httpForward": { // local machine Tomcat instance
 "host": "127.0.0.1",
 "port": 8080,
 "scheme": "HTTP"
 },
 "times": {
 "unlimited": true
 }
 })
 .then(
 function () {
 // forward all other request to QA environment
 mockServerClient("localhost", HTTP_PORT)
 .mockAnyResponse({
 "httpRequest": {
 "path": "/.*"
 },
 "httpForward": { // QA environment load balancer
 "host": "192.168.50.10",
 "port": 443,
 "scheme": "HTTPS"
 },
 "times": {
 "unlimited": true
 }
 })
 .then(
 function () {
 console.log("created expectations");
 },
 function (error) {
 console.log(error);
 }
 );
 },
 function (error) {
 console.log(error);
 }
 );
 });
console.log("started on port: " + HTTP_PORT);
// stop MockServer if Node exist abnormally
process.on('uncaughtException', function (err) {
 console.log('uncaught exception - stopping node server: ' + JSON.stringify(err));
 mockserver.stop_mockserver();
 throw err;
});
// stop MockServer if Node exits normally
process.on('exit', function () {
 console.log('exit - stopping node server');
 mockserver.stop_mockserver();
});
// stop MockServer when Ctrl-C is used
process.on('SIGINT', function () {
 console.log('SIGINT - stopping node server');
 mockserver.stop_mockserver();
 process.exit(0);
});
// stop MockServer when a kill shell command is used
process.on('SIGTERM', function () {
 console.log('SIGTERM - stopping node server');
 mockserver.stop_mockserver();
 process.exit(0);
});

To start the process install the npm module and launch Node.js, as follows:

npm i
node server.js