How to build a replicated ehcache through firewall and not to die trying

It's assumed that:

  • You already have a java application and you have an ehcache instance running in your program with 1 cache configured to replicate.
  • You want to connect 1 instance to another instance you have in a remote machine
  • The remote machine you are connecting to is located behind a firewall.
  • You have been given access to only 1 port to make an ssh connection to the remote (firewalled) machine.
Ehcache uses RMI to connect the remote instances. When the cache in host 1 tries to connect to cache in host 2, RMI opens a new server socket in host 1 to listen for incoming connections from the host 2.
The problem here is that these random ports are not accesible to remote hosts because the hosts are behind a firewall.

So to fix it, we need to configure ehcache to only use 2 ports. The "remoteObjectPort" does the magic. So we have this ehcache.xml configuration:
  • 1 server port for the ehcache server to listen to other ehcache servers.
  • 1 server port for the ehcache cache to listen to incoming connections (this cache is the actual map in memory that is being replicated).
And the related properties are these. Inject it with System.setProperties(ehcacheProperties) before loading the ehcache instance in your program.
Open the 4 tunnels to the remote machine:

  • 1 local port for the ehcache server to listen to incoming connections from remote cache server
  • 1 local port for the ehcache cache for incoming connections from the remote cache
  • 1 remote port for remote ehcache server to listen incoming connections from our local host
  • 1 remote port for remote ehcache cache to listen to incoming connections from our local host

Run java programs on both machines (local and remote) with the "java.rmi.server.hostname" so the RMI server reports to the other RMI (the remote one) that it's address is "127.0.0.1" rather than any other IP it may has; so the tunnels can work. If you have any comment or suggestion please contact me.

Comments

  1. for IT theDecember 7, 2017 at 5:34 AM

    Hi, Great.. Tutorial is just awesome..It is really helpful for a newbie like me.. I am a regular follower of your blog. Really very informative post you shared here. Kindly keep blogging. If anyone wants to become a Java developer learn from Java Training in Chennai. or learn thru Java Online Training in India . Nowadays Java has tons of job opportunities on various vertical industry.

    ReplyDelete
  2. Oanh TrDecember 27, 2018 at 5:42 AM

    Christmas has come and New Year is coming. One of the things I will do next year is to follow your new posts. It's because they provide what I need. Your articles are informative and great. Stay healthy and write more posts. Thanks
    Short Ride || Kindergarten Dress Up games for kids for school || Moto X3M 2 free on abcya3 games

    ReplyDelete
  3. priyaJanuary 28, 2019 at 7:01 AM

    Thanks for the good words! Really appreciated. Great post. I’ve been commenting a lot on a few blogs recently, but I hadn’t thought about my approach until you brought it up. 
    Data Science course in rajaji nagar
    Data Science with Python course in chenni
    Data Science course in electronic city
    Data Science course in USA
    Data science course in pune | Data Science Training institute in Pune
    Data science course in bangalore

    ReplyDelete

Post a Comment

Popular posts from this blog

Android 3D Model Viewer Open Source

So finally I decided to publish my 3D model Viewer android app on the Google Play Market :)

This app is about drawing 3D objects in android using OpenGL ES 2.0; and its Open Source as my other projects, so people can either contribute, start a similar project based on that or just learn how to do it by looking at the source code.

Although there is already similar apps on the market and lots of 3D frameworks out there, neither of the published apps are Open Source.

So I wanted to learn how 3D works and I think the best way to understand how it works is by looking at how matrices transforms the objects in space and how pixels are drawn to the screen. Thats why this app does not use any third party framework.

So far the app serves as a model viewer, but I have some ideas of what can be done with the code; or as I prefer to think of it, mini-3D-framework.  So for example, I am thinking in creating my very first and simple mini-game and I want to do it in 3D as it is a matter I really like…
Read more

Google Drive FTP Adapter

Image
Google Drive FTP Adapter
This open source application lets you connect your FTP applications to your Google Drive files through the FTP protocol rather than using the Official's Google Drive client.
This custom google drive client was created because official's one can't be reinstalled in a new PC without having to redownload all your drive files again, from the cloud to your local PC.  So if you have hundred of Gigas and a regular ADSL it would take weeks to complete. Also, because the official client does not support FAT32 partitions and I used to have all my files in one of this partitions.
So this application basically starts a FTP server in your local machine emulating that it is hosting your google drive files, acting as a gateway. Once this setup is done, you can connect any FTP client to connect to your google drive files. I use it in conjunction with Beyond compare to compare my local files (stored anywhere in my hard drive) and compare them to ones I have in the…
Read more