Common Queue Configuration Variables

 

Description

The following configuration variables are used by several agents that implement queue functions. Using these parameters allows the user to control queue behavior, including which of the following strategies to take when the queue is full:

 

Configuration Variables

 

droppedDataCount

A read-only integer value that identifies how many products have been dropped because the queue was full.

dropDataIfQueueFull

true or false. If false then the input will be blocked when new input product is available and the queue is full.

If true then data will be dropped when a new input product is available and the queue is full. The dropping strategy is determined by the value of useProductSalienceWhenDropping

logDroppedData

true or false. If true this indicates that periodic messages should be sent to the log indicating how many products have been dropped because the queue was full. Messages are not sent every time a product is dropped.

numberOfItemsOnQueue

A read-only parameter that can be used to monitor how many items are on the queue. This is for monitoring purposes only and is only updated every few seconds.

queuePausesAllowed

true or false. Defaults to true. Indicates that it is ok to hold the contents of the queue while the system performs maintenance tasks such as checkpointing.

queueSize

Defaults to 20. The maximum size of the queue.

queueThreadPriority

Defaults to 5. An integer that identifies the Java Thread priority for the thread that takes products off of the queue to send to the outputs.

useProductSalienceWhenDropping

true or false. This determines the strategy to use when dropping products. If true then product salience is used to select which product to drop. If false then the new product (not yet added to the queue) is dropped.

Product Metadata - Salience

Products may have optional metadata to help determine which product will get dropped from the queue if the queue fills. The metadata tag on the product is salience. This has an integer value. If it becomes necessary to drop a product then the product with the lowest salience can be dropped. A product with no explicit salience is treated as if it had salience = 0 .

 

Revised 3 June 1999