Cluster Creation or Connection Errors immediately following OpsCenter Install

Problem

Summary

Using the standard DSE and OpsCenter install instructions, running OpsCenter for the first time and trying to Create a Cluster the following errors are seen:
 

Error 1: Unable to create cluster: Unable to Connect

or

Error2: The following packages are already installed ‚ <listing of DSE/Cassandra files and directories>

Symptoms

This situation arises when DSE and OpsCenter are being installed for the first time:

Cause

After installing both DSE and OpsCenter, OpsCenter is started and the user‚ receives‚ the message "Create a New Cluster or Connect to a Cluster". However, this is problematic because

a) To create a cluster,‚ DSE cannot already be installed.

b) To connect to a cluster,‚ DSE must be currently running.

The DSE install does not automatically start the DSE process, nor do the instructions say to start DSE.‚ 

The following scenario will help to understand the problem.

• Install DSE on the machine - 10.15.19.201

• Install OpsCenter on machine  - 10.15.19.201
• Connect to OpsCenter
• OpsCenter prompts: Create a Cluster OR Connect to a Cluster.

Either option will fail when referring to 10.15.19.201.‚  This is because in order to‚ Connect to a Cluster‚ DSE must be running, which it is not. ‚ In order to‚ Create a Cluster‚ the machine(s) to be configured cannot contain the DSE/Apache Cassandra software, which in this case it does contain the software. So regardless of the path taken, a failure will occur.

Solution

Solution 1 - Connect to a Cluster

1. Use the OpsCenter Install documentation to insure that all prerequisites for OpsCenter have been followed and the verify proper way to start OpsCenter. ‚ This can be obtained for the latest version of OpsCenter by visiting http://datastax.com/docs
2. Start DSE or Apache Cassandra after installing. ‚ This is done by starting it as a service or a standalone process. Visit‚ http://datastax.com/docs‚ to find the correct startup sequence.
3. Verify that DSE/Apache Cassandra is running. ‚ Using a command such as 'ps aux | grep dse' which will verify that the process is running.‚ 
4. Start OpsCenter.
5. Choose "Connect to a Cluster" if prompted and enter the IP for the machine running DSE.

Solution 2 - Create a Cluster

1. Start OpsCenter
2. Choose "Create a Cluster"
3. Provide information such as IP for machines that will run the nodes. ‚ These machines must contain no DSE software.