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:
- Block the input
- Drop the new input
- Scan the input products and the products already on the queue and drop the product with the lowest salience.
Configuration Variables
A read-only integer value that identifies how many products have been dropped because the queue was full.dropDataIfQueueFull
true
orfalse
. Iffalse
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 useProductSalienceWhenDroppinglogDroppedData
true
orfalse
. Iftrue
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
orfalse
. Defaults totrue
. 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
orfalse
. This determines the strategy to use when dropping products. Iftrue
then product salience is used to select which product to drop. Iffalse
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 issalience
. 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 hadsalience = 0
.
Revised 3 June 1999