Load balancing question

[Former Member]

I have a question about the SAP J2EE Load Balancing. To use Load balancing I want to change the “LoadbalancingPower” Parameter regulary.

In SAP docu I found the following sentences:

“To enable the changes to take effect, choose (Save Properties) on the toolbar and restart the Service Manager.”

Does anybody know how to restart the service Manager without restart the whole server?

Best regards

Nils Kloth

[Former Member]

Hi Nils,

guess you're refering to J2EE Engine 6.20, right?

unfortunately, restarting the service manager only is not possible. The reason for this is that this Manager is a core component, and a lot of server components (the services) depend on it. Therefore, restarting the manager will trigger restart of the services as well, hence the restart of the server is necessary.

Hope that explains it a bit.

[Former Member]

Hi Ivaylo,

the reason for my question is the following problem:

My company uses an E-Selling Enviroment.

We develop for these Webshop and have to deploy our updates regulary.

Therefore we configure two server nodes. Now we want change the loadbalancing, so that on one server will start no more new sessions.

After this server is clean of Sessions we want to update this server/deploy the *.ear file.

Then we want to change Loadbalancing, so that all new user login on the updated server and the other server is not in use.

Then we want to deploy the file on this server too and want to switch loadbalancing to 50/50.

During this process we don't want to restart a server, where users are logged in, because we don't want to kick out a logged user.

I hope I explain the problem well.

Therefore I ask for the restart of the service manager.

Do you know another way to handle this update problem?

[iavor_petkov]

Hi Nils,

You are basically trying to achieve hot deployment of your application. This is not possible currently with a single cluster.

Changing the loadbalancing power of a node is not the right way to switch it off from the http loadbalancing.

Instead if you want to exclude a node from the loadbalancing, you should:

1. telnet to the Engine

2. jump to the respective application node

3. type suspend

If you want later to add it back to the loadbalancing, then

1. telnet to the Engine

2. jump to the respective application node

3. type resume

However, this will not help you to achieve hot deployment.

The reason is that:

1. Deployment is clusterwide - that is you are deploying on first on the state controller, then all active application nodes synchronize from it.

2. During deployment the application is stopped, clusterwide.

3. When an application node joins the cluster it synchronizes applications from the state controller to get the currently operational version. So even if you somehow succeed in deploying a different version on the application node (for example by running it with a different cluster where you perform deployment), when it joins the cluster, this inconsistency will be removed and it will get again the old, currently active version of the application.

I hope this was helpful.

Best Regards: Iavor