Use SVN Deployment Synchronizer to sync artifacts in multiple nodes of a WSO2 cluster

Deployment Synchronizer has the ability to sync deployed artifacts in a multiple nodes cluster as soon as the deployment happened. It's necessary to have the same configuration among each node of the cluster since the whole mechanism is to work as a single system (virtually). If a particular node doesn't have the same configuration like the rest of the nodes, it breaks the clustering model. As an example if a proxy service which doesn't include in Node 1, has been invoked through the load balancer and it won't fulfill the work division among nodes as it intended to be.

WSO2 products use SVN (SubVersioN) deployment synchronizer in order to have the syncing process of deployed artifacts like endpoints, proxy services, sequences and etc. The Subversion repository is used to sync the contents in the local sync directory (the axis2 repo directory, /repository/deployment/server, by default).

Now let's see how to setup the SVN DepSync repository with WSO2 products. Before going further into setup, first of it's necessary to select the suitable SVN version. It's advised to only select SVN version 1.7 or 1.8 for the products based on Carbon 4.4.x ( if you're using products based on Carbon 4.2.x and below, please use only SVN version 1.6 ).

Following files needed to be downloaded and save in the product environment to continue with SVN Dep Sync configuration.

• Download SVNKit from here and save it into the <PRODUCT_HOME>/repository/components/dropins folder. 

• In order to function the SVNKit properly, download trilead-ssh2-1.0.0-build215.jar file from here and save it in <PRODUCT_HOME>/repository/components/lib folder. 

After completing the pre-requesties, let's move to configure DepSync on manager and worker nodes. 

Deployment synchronizer configuration done in /repository/conf/carbon.xml file and go to <DeploymentSynchronizer> sub section in carbon.xml to make necessary changes.


Steps to Enable DepSync on the manager node

• To enable the Deployment synchronizer, the value should be set to 'true' for <Enabled> tag 
• Since manager node responsible for receiving server requests and committing changes in local repository to central repository, the value for <AutoCommit> should be 'true' 
• <AutoCheckout> value should changed to 'true'. Once changes are committed in central repository, it should automatically checked out them to local repository of the node. 
• We're using Subversion as repository type here :
  <RepositoryType>svn</RepositoryType>
• Location of the SVN repository should be specify:
  <SvnUrl>https://svn.example.org/depSync</SvnUrl>
• <SvnUsername> and <SvnPassword> must specified with the Username and password of SVN repository respectively. If the tenant specific configuration has to be made, set the value for to 'true'. 

That's it with the manager node configuration. So the manager node deployment synchronization configuration should looks like this,

<DeploymentSynchronizer>
<Enabled>true</Enabled>
<AutoCommit>true</AutoCommit>
<AutoCheckout>true</AutoCheckout>
<RepositoryType>svn</RepositoryType>
<SvnUrl>https://svn.example.com/depsync.repo/</SvnUrl>
<SvnUser>rep1</SvnUser>
<SvnPassword>reppass</SvnPassword>
<SvnUrlAppendTenantId>true</SvnUrlAppendTenantId>
</DeploymentSynchronizer>

Now move to worker node configuration.

Steps to Enable DepSync on the worker nodes

Worker node has the same configuration for DepSync like the manager node except the usage of <AutoCommit>. Since worker node doesn't receive any server requests to be handled and the committing part isn't associated with worker nodes, <AutoCommit> value set to be 'false'. This is the DepSync configuration for Worker nodes.

<DeploymentSynchronizer>
<Enabled>true</Enabled>
<AutoCommit>false</AutoCommit>
<AutoCheckout>true</AutoCheckout>
<RepositoryType>svn</RepositoryType>
<SvnUrl>https://svn.example.com/depsync.repo/</SvnUrl>
<SvnUser>rep1</SvnUser>
<SvnPassword>reppass</SvnPassword>
<SvnUrlAppendTenantId>true</SvnUrlAppendTenantId>
</DeploymentSynchronizer>

So that's it about how to configure deployment synchronizer in a clustered environment. I will discuss about some of the use cases of DepSync in my upcoming posts.