Process of webserver starting

Question

This question is kind of related to our web application and it is bugging me from last few months. So we use linux server for database, application and we have our custom built java web server. If we do any change in source code of application, we build a new jar file and replace the existing jar file with new jar file. Now update to take place in live application, we just execute a HTML file which contains this kind of code :

<frameset rows="100%"?
<frame src="http://mydomain.com:8001/RESTART"&gt;
</frameset>

How does this opening of port make the application to use new jar file?

Answer 1

The webserver is instructed to give the /RESTART URL special treatment. This can either be through a mapping to a deployed servlet, or through a hardcoded binding to a web container action.

It is very common to have URLs with special meaning (usually protected by a password) allowing for remote maintainance, but there is no common rule set. You can see snapshots of the Tomcat Administration console at http://linux-sxs.org/internet_serving/c516.html

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EDIT: I noticed you mentioned a "custom built web server". If this web server does not provide servlets or JSP's - in other words conforms to the Servlet API - you may consider raising the flag about switching to a web server which do.

The Servlet API is a de-facto industry standard which allows you to cherry-pick from a wide array of web servers from the smallest for embedded devices to the largest enterprise servers spreading over multiple physical machines, without changing your code. This means that the hard work of making your application scale has been done by others. In addition they probably even made the web server as fast as possible, and if not, you can pick another where they did.

Answer 2

You're sending an HTTP GET to whatever's listening on that port (presumably your web server). The servlet spec supports pre- and post-request filters, so the server may have one set up to capture this particular request and handle it in a special fashion.