WSO2 ESB Clustering concept

Question

I am new to WSO2 ESB clustering, actually I'm still learning about it. I still don't understand the concept here.

In my case, I installed WSO2 ESB on 2 servers. My questions are:

1. Were both of the WSO2 ESB working as one application or as two separate applications?
2. If I configure one WSO2 ESB, will the other ESB have the same configuration?
3. If I configure a VFS proxy service the ESB to poll a file from specific directory, will it create a conflict when I poll a file? I think that both of the ESB will poll the same file.

Please enlighten me :) Thanks...

Answer 1

1. Were both of the WSO2 ESB working as one application or as two separate applications?

No, both ESBs are separate applications. The clustering is done mainly to ensure availability and scalability. So even a member in a cluster fails, others continue to operate.

2. If I configure one WSO2 ESB, will the other ESB have the same configuration?

Each ESB can get the same cluster configuration, but each will be separately identified by the LB that is fronting the cluster. Therefore, each member will get different IP addresses and even they can use different member-port to create cluster.

3. If I configure a VFS proxy service the ESB to poll a file from specific directory, will it create a conflict when I poll a file? I think that both of the ESB will poll the same file.

Each request is independently handled by separate ESB depending on the load balancer algorithm of the fronting LB. When two threads poll the same file, there can be conflicts. Since VFS transport deals with file operations, there are certain times that these can fail due to unavailability of some resources. In such a case, VFS transport is equipped with the following fault handling mechanism.

Answer 2

Check my answers inline.

1. Were both of the WSO2 ESB working as one application or as two separate applications?

In any cluster, applications or servers are working together to provide a high availability to the end users. It will work as one single server (application).

2. If I configure one WSO2 ESB, will the other ESB have the same configuration?

Yes. You can achieve this with the deployment synchronization. It will make sure all your changes are evenly distributed among other nodes of the cluster.

3. If I configure a VFS proxy service the ESB to poll a file from specific directory, will it create a conflict when I poll a file? I think that both of the ESB will poll the same file.

No. Since only one server is active at once. This should not be a problem.

You can learn more from the following link:
http://docs.wso2.org/display/CLUSTER420/Clustering+WSO2+Products

Answer 3

If you point the same directory in a clustered environment, both proxy services will try to poll files and cause issues. Therefore if you want to poll files in a clustered environment, best practice is to use inbound endpoints [1]. But if it is necessary to use proxy services you can apply the following property in your proxy, so that the proxy service will only operate in one server. Thus there will not be any conflicts between the two proxy services. Please refer [2] to further clarify this.

<parameter name="transport.vfs.ClusterAware">true</parameter>

[1]-https://docs.wso2.com/display/EI620/File+Inbound+Protocol

[2]-https://docs.wso2.com/display/ESB500/VFS+Transport