Creating and scaling Dynamic Clusters using wlst

In my previous article, Creating and scaling Dynamic Clusters in Weblogic 12c, I described the creation and scaling of Dynamic Clusters. I used the Weblogic Console to create the Dynamic Clusters and change the number of servers.

Most of the time you will use some wlst scripting to create and manage your Weblogic environments.
In this article I will show you how to create Dynamic Clusters en how you can scale them.

The example scripts from the Oracle documentation where used as base for the following script.
It is just a simple create script to show you how easy it is to create a Dynamic Cluster via wlst. So no fancy functions and exception handling in there. Yet ...

createDynamicCluster.py

print '--- Set properties for dynamic Cluster creation'
clusterName='dyna-cluster'
serverTemplate='dyna-server-Template'
serverNamePrefix='dyna-server-'
listenAddress='192.168.100.4${id}'
listenPort=8000
listenPortSSL=9000
maxServerCount=2

print '--- Connect to the AdminServer'
try:
  connect('weblogic','Welcome01','t3://hostname.domain.local:7001')
except err:
  print "--- Can't connect to AdminServer, "+err
  sys.exit(2)

print '--- Start an edit session'
edit()
startEdit()

print '--- Creating the server template '+serverTemplate+' for the dynamic servers and set the attributes'
dynamicServerTemplate=cmo.createServerTemplate(serverTemplate)
dynamicServerTemplate.setListenAddress(listenAddress)
dynamicServerTemplate.setListenPort(listenPort)
dynamicServerTemplateSSL=dynamicServerTemplate.getSSL()
dynamicServerTemplateSSL.setListenPort(listenPortSSL)

print '--- Creating the dynamic cluster '+clusterName+', set the number of dynamic servers and designate the server template to it.'
dynamicCluster=cmo.createCluster(clusterName)
dynamicServers=dynamicCluster.getDynamicServers()
dynamicServers.setMaximumDynamicServerCount(maxServerCount)
dynamicServers.setServerTemplate(dynamicServerTemplate)

print '--- Designating the Cluster to the ServerTemplate'
dynamicServerTemplate.setCluster(dynamicCluster)

print '--- Set the servername prefix to '+serverNamePrefix
dynamicServers.setServerNamePrefix(serverNamePrefix)

print '--- Set Calculate Listen Port and Machinename based on server template'
dynamicServers.setCalculatedMachineNames(true)
dynamicServers.setCalculatedListenPorts(true)

print '--- Save and activate the changes'
save()
activate()
serverConfig()

Running the script with wlst will produce the following output and will create a Dynamic Cluster with two Dynamic Servers.

[oracle@wls01 ~]$ ${WL_HOME}/common/bin/wlst.sh createDynamicCluster.py
Initializing WebLogic Scripting Tool (WLST) ...

Welcome to WebLogic Server Administration Scripting Shell

Type help() for help on available commands

--- Set properties for dynamic Cluster creation
--- Connect to the AdminServer
Connecting to t3://wls01.domain.local:7001 with userid weblogic ...
Successfully connected to Admin Server "AdminServer" that belongs to domain "demo_domain".

Warning: An insecure protocol was used to connect to the
server. To ensure on-the-wire security, the SSL port or
Admin port should be used instead.

Start an edit session
Location changed to edit tree. This is a writable tree with
DomainMBean as the root. To make changes you will need to start
an edit session via startEdit().

For more help, use help('edit')

Starting an edit session ...
Started edit session, please be sure to save and activate your
changes once you are done.
--- Creating the server template dyna-server-Template for the dynamic servers and set the attributes
--- Creating the dynamic cluster dyna-cluster, set the number of dynamic servers and designate the server template to it.
--- Designating the Cluster to the ServerTemplate
--- Set the servername prefix to dyna-server-
--- Set Calculate Listen Port and Machinename based on server template
--- Save and activate the changes
Saving all your changes ...
Saved all your changes successfully.
Activating all your changes, this may take a while ...
The edit lock associated with this edit session is released
once the activation is completed.
Activation completed

As you might expect, it is way faster than clicking through the Weblogic Console.


Next step will be to scale the Dynamic Cluster up to four Dynamic Servers.

scaleDynamicCluster.py

print '--- Set properties for dynamic Cluster creation'
clusterName='dyna-cluster'
maxServerCount=4

print '--- Connect to the AdminServer'
try:
  connect('weblogic','Welcome01','t3://wls01.domain.local:7001')
except err:
  print "Can't connect to AdminServer, "+err
  sys.exit(2)

print '--- Start an edit session'
edit()
startEdit()

print '--- Change the maximum number of dynamic servers'
cd('/Clusters/%s' % clusterName )
dynamicServers=cmo.getDynamicServers()
dynamicServers.setMaximumDynamicServerCount(maxServerCount)

print '--- Save and activate the changes'
save()
activate()
serverConfig()

Running the script with wlst will produce the following output and will scale up to four Dynamic Servers.

[oracle@wls01 ~]$ ${WL_HOME}/common/bin/wlst.sh scaleDynamicCluster.py

Initializing WebLogic Scripting Tool (WLST) ...

Welcome to WebLogic Server Administration Scripting Shell

Type help() for help on available commands

--- Set properties for dynamic Cluster creation
--- Connect to the AdminServer
Connecting to t3://wls01.domain.local:7001 with userid weblogic ...
Successfully connected to Admin Server "AdminServer" that belongs to domain "demo_domain".

Warning: An insecure protocol was used to connect to the
server. To ensure on-the-wire security, the SSL port or
Admin port should be used instead.

--- Start an edit session
Location changed to edit tree. This is a writable tree with
DomainMBean as the root. To make changes you will need to start
an edit session via startEdit().

For more help, use help('edit')

Starting an edit session ...
Started edit session, please be sure to save and activate your
changes once you are done.
--- Change the maximum number of dynamic servers
--- Save and activate the changes
Saving all your changes ...
Saved all your changes successfully.
Activating all your changes, this may take a while ...
The edit lock associated with this edit session is released
once the activation is completed.
Activation completed

As mentioned before, the scripts are very limited and just show you how easy it is to create Dynamic Clusters using wlst. The scripts can be made as comprehensive as you need (want) them to be.
I will create some more examples and post them as I get them ready.

Imagine the possibilities when you create scripts you can connect to your monitoring system. Capacity on demand!

Creating and scaling Dynamic Clusters in Weblogic 12c

Introduced in Weblogic 12.1.2, dynamic clusters is a great feature to scale your private cloud.
Dynamic clusters provides you easy scaling of Weblogic clusters by adding and removing managed server instances on demand. They contain one or more dynamic servers. These dynamic servers are based on a single servertemplate that guarantees that every member of the cluster is exactly the same.

Creating Dynamic Clusters

Let's take a look at some of the possibilities as we create a dynamic cluster.

I have created a virtualbox environment.
This environment consists of four VM's with the following specs.

• 2 vCPU's
• 4 Gb memory
• 50 Gb disk

• Oracle Linux 6.6
• Java 1.7.0_75
• Weblogic 12.1.3.0.2

I created a simple domain called demo_domain with only an AdminServer and four machines.
After unpacking the domain to the four servers, the nodemanagers where started and are reachable by the AdminServer.

Now let go through the process of creating a dynamic cluster.

Open the Weblogic Console and navigate to Environment -> Clusters
Lock and Edit the domain in the Change Center
note. I make it a good practice always creating a domain in production mode, even in Development and Test.

Create a new dynamic cluster

New -> Dynamic Cluster

Provide the Clustername

Cluster name: dyna-cluster
Click Next

We will start of with a cluster containing two dynamic servers.

Number of Synamic Servers: 2
Server Name Prefix: dyna-server-
Click Next

For this demo all machines will take part.

Select 'Use any machine configured in this domain'
Click Next

Assign each dynamic server unique listen ports

Listen Port for First Server: 8000
SSL Listen Port for First Server: 9000

Click Next

Summary screen

Click Finish

With the creation of the Dynamic Cluster there is also a Server Template created for it.

Server templates

A single server template provides the basis for the creation of the dynamic servers. Using this single template provides the possibility of every member being created with exactly the same attributes. Where some of the server-specific attributes like Servername, listen-ports, machines, etc. can be calculated based upon tokens.

You can pre-create server templates and let Weblogic clone one when a Dynamic Cluster is created.

When none is available a server template is create with the Dynamic Cluster. The name and the listen ports are the only server template attributes that you provide during Dynamic Cluster creation.

Before we activate the changes to the domain, we are going to make a change to the server template.

As an example we are going to demonstrate the use of tokens for server-specific configuration. 

Navigate to Environment -> Clusters -> Server Templates

Click on the name: dyna-server-Template

We are going to use the ${ID} token in the Listen Address

Listen Address: 192.168.100.4${ID}
Click Save

The last digit of the listen address is used to make the listen address dynamic.

Activate changes in the Change Center of the Weblogic Console.
After activation the cluster and two managed servers are created.

We can now start the two servers.

In the previous steps we have added a dynamic cluster with two dynamic servers, based on a single server template, to the domain.

Scaling a Dynamic Cluster

When the capacity is insufficient and you need to scale-up, you can add dynamic servers on demand.
It requires only a few clicks.

Navigate to Environment -> Clusters

Click dyna-cluster

On the Configuration tab go to the Servers tab

Change the Maximum Number of DynamicServers to: 4
Click save

Activate changes in the Change Center of the Weblogic Console.
After activation two Dynamic Servers are added to the Dynamic Cluster.

Start the two new Dynamic Servers and you have doubled you capacity.

Scaling down works exactly the same.
Just lower the Maximum Number of DynamicServers and activate.

A few points to keep in mind when scaling up or down.

Up

• New dynamic servers are not started upon creation
• Think before you act with the use of Tokens.
  For example.
  In our demo, the number of Dynamic servers can't grow beyond nine servers, since we use the ${ID} as last digit of the listen address.

Down

• Dynamic Servers above the new Maximum have to be shutdown before the change can be activated.
• Dynamic Servers are removed in order, Last -> First
  (In our demo dyna-server-4 gets removed first, then dyna-server-3, etc..)
• You cannot remove a Dynamic Server directly from the Environment -> Servers page