Query Service

The Watson Explorer Engine query service uses local configuration information to identify the collection service that is associated with a given search collection, and then contacts that collection service to locate the indexer service that is associated with that search collection. The query service then forwards the query to that indexer service, and retrieves and returns the results of the query.

Once started, the query-service will automatically restart itself if it crashes. The query-service maintains a set of general-purpose threads to process the web requests for search results or cached pages. The service attempts to maintain at least Minimum idle threads and at most Maximum idle threads ready for handling new requests. The defaults should normally be acceptable.

Important: Instructing the query service to shut down (via the API or by using the Watson Explorer Engine administration tool's Management > Services > Search Engine tab) when that service is under heavy query load may result in that service becoming unresponsive rather than terminating. In this case, you must terminate the service at the operating system level. However, there is normally no reason to manually shut down the query service because that is usually only done when shutting down Watson Explorer Engine. To shut down Watson Explorer Engine and terminate all Watson Explorer Engine-related processes, use the velocity-shutdown command.

The query service accepts HTTP connections on a specified port. It also accepts HTTPS connections, if you supply your own SSL certificate in PEM format with private key. You can allow other hosts to contact this query service by entering approved IP addresses or wildcards (such as 192.168.0.*) in the Allowed IPs field on the Management > Services > Search Engine > Options screen in the Watson Explorer Engine administration tool. This is usually done to allow Watson Explorer Engine front-end installations to contact a back-end query service in a multi-tier architecture, or to permit queries from Application Builder or BigIndex components.