Testing Your Failover Configuration

Important: The suggestions for Failover and Load Balancing given in this and subsequent sections are intended for development systems only. The source testing functionality described is designed for testing purposes only, and has not been developed to handle the volume of requests required by a production system.

In production systems, Load Balancing should be achieved by using a dedicated load balancer configured by your network administrator.

If you are using multiple mirrors of an index, Watson™ Explorer Engine provides an easy way to verify that failover between those mirrors is working correctly. This is done by disabling pings, which are the network response that the vse-heartbeat test (discussed earlier) uses to determine if a source is available.

To test failover, use your web browser to visit a Watson Explorer Engine administration tool that is running on any of the servers on which any portion of a mirror of your index is replicated, and select Management from the list at the top of the Watson Explorer Engine administration tool screen. Select Services from the left menu, and click the Search Engine tab. You will see a screen like the one shown in Figure 1.

Figure 1. Disabling Search Engine Responses to Verify Failover

To disable responses to pings from the query service, click the ignore pings button on the top right hand side of the display screen. This causes the Watson Explorer Engine administration tool to return an error message when any incoming network ping of the search engine is detected. The following message displays in a yellow text box when pings are disabled:

    The query service is not responding to pings.
    Currently responding with the error: [Pings disabled by admin].

Once you have disabled ping responses, you can then display the Distributed Source Selector that you created to manage index use across all of your replicas, and perform a test search against your collection by entering a test phrase in the Test with project... box displayed in the left column of the Watson Explorer Engine administration tool. This displays the results of the test search in a new window with debugging enabled.

Below the summary snippet for each individual search result for your query, you will see the URL of the search result that was returned. To the right of this are two text fields, which are the name of the source that was used and the sequence number of that search result. If you refresh the window containing the search results multiple times, you will note that the name of the source that was consulted never includes the name of any mirror that is stored on the system that you disabled. This indicates that the search test is actually ignoring this host and using the other sources that make up your distributed index.

To re-enable the mirror that you disabled for testing, revisit the Watson Explorer Engine administration tool running on that host, and click respond to pings, which causes the search engine to stop returning an error when pings are detected, and to resume normal responses.