Syed Jahanzaib Personal Blog to Share Knowledge !

April 10, 2013

Lotus Domino ICM (Internet Cluster Manager for HTTP failover/load balancing)

Filed under: IBM Related — Tags: , , — Syed Jahanzaib / Pinochio~:) @ 4:06 PM

Recently we configured Lotus Domino clustere in our company.Everything worked fine, Failover to secondary and move back to primary server when available working good, but the HTTP does not works this way. Browsers themselves are not cluster aware, they ask for specific host-names. For example if one of my primary server goes down, then the web mail users wont be able to access there mail from the primary server mail address.

For this purpose I googled a  little bit and found out that Domino ICM (Internet cluster manager) can fulfill our requirement. This makes our web mail servers highly available to clients. You can run the ICM on a Lotus Domino server configured in clusters (not necessarily clustered). The ICM supports the HTTP protocols acting as an High Availability Bridge between HTTP clients and the Domino Web servers in a cluster. ICM also maintain information about the availability of servers and databases in the cluster.  ICM Sends periodic probes to the Web servers in the cluster to determine their availability.

ICM installation and configuration was a piece of cake, in fact there was nothing to configure much 🙂 You should include the ICM configuration information on every Web server in the cluster, not just the server on which you run the ICM.
This is done because each Web server uses its own Server document to determine how to generate URLs that refer to the ICM
Following is a small howto for my future reference.

I assume you already have Primary and secondary server (clustered) configured. Following is example of network

D1 = primary domino server
D2 = secondary domino server
D3 = domino server for ICM for HTTP

From your primary server ,

1- Register a new server ID with the name of D3
2- Install Domino on 3rd server , run its setup, and configure it as Addition server and provide it D3.id that you created in step 1.
3- Add D3 in existing cluster
3- Goto D3 console, and quit http server (use command tell http quit), otherwise it will gonna conflict with the ICM service which also uses the same tcp 80 port. OR you can change ports as per your requirement IF you want to run ICM and HTTP on same server.
4- Load ICM by issuing following command at D3 console.

load icm

Now from your client end, browse to http://D3 and you will be redirected to the first available server i.e http://D1
For test purpose, quit D1 server, wait few seconds,

Now browse again to http://D3 and this time you will be redirected to http://D2 instead of D1 because ICM maintain the list of available server in the list and will redirect request to first available server.

When an HTTP client is connected to a server that fails, the client receives a typical browser message stating that the server is not responding. To fail over to a different replica, the user must contact the ICM again by entering the D3 address in URL again.

Some information provided in this article have been taken from multiple external resources. For example
Understanding IBM Lotus Domino server clustering By Reetu Sharma /Ranjit Rai

Regard’s
Syed Jahanzaib

%d bloggers like this: