FDispatch Test

Query processing is the stage of the search where the query is received from (for example, the Search Center) and is processed to apply certain rules or expansion before being matched to the content of the index. Query processing in FAST Search for SharePoint 2010 is a set of components (QR Proxy, QR Server, and Fdispatch) that receive the query from the FAST Query SSA (FAST Search Query module), process it, and pass it onto the Query Matching component. The query dispatching part (Fdispatch) passes the query to the index columns and eventually to any index partitions. There is also a query dispatcher (Fdispatch) located on each query matching server, distributing queries across index partitions.

If the query load to the dispatchers increase, query queues build up, thereby delaying query processing significantly. Using this test, you can continuously monitor the query load on each of the query dispatchers configured on the query matching servers, observe variations in the length of the query queues, and proactively isolate the following:

• a probable overload condition; you can even accurately identify which query dispatcher is handling the maximum load
• a potential handle leak and the query dispatcher responsible for the same;
• latencies in query processing

Target of the test : A FAST Search Server 2010 for SharePoint

Agent deploying the test : An internal agent

Outputs of the test : One set of results for every query dispatcher configured on each query matching server in the FAST Search Server 2010 for SharePoint farm.

Configurable parameters for the test

Parameter	Description
Test period	How often should the test be executed
Host	The host for which the test is to be configured.
Port	Refers to the port used by the specified host. By default, this is 13280.

Measurements made by the test

Measurement	Description	Measurement Unit	Interpretation
Active running queries	Indicates the number of queries that are currently active on this query dispatcher.	Number	This is a good indicator of the current load on the dispatcher. Compare the value of this measure across dispatchers to identify the dispatcher that is handling maximum load currently.
Total number of queries dispatched	Indicates the number of queries that have been dispatched by this query dispatcher since the last index set change.	Number
Number of open file handles	Indicates the number of file handles that are currently open in this query dispatcher.	Number	The maximum number of open file handles for fdispatch is 1014. If the value of Number of open file handles exceeds this limit, it is a cause for concern, as it could indicate a handle leak.
Max number of open file handles	Indicates the maximum number of open file handles in this query dispatcher.	Number
Number of queued queries	Indicates the number of queries to this query dispatcher that have been temporarily put on hold by adding them to a wait queue.	Number	Ideally, the value of this measure should be low. A high value or a consistent increase in this value is indicative of latencies in query processing or an overload condition.