Configuring the Assignment of Queues to WIS Processes

When iProcess Engine starts up, the WQS process is responsible for assigning all the work queues to WIS processes.

By default, queues are assigned to WIS processes dynamically, using the round-robin or on-demand method (as determined by the WQS_ROUND_ROBIN parameter in the staffcfg file, which is located in the SWDIR\etc directory- see WQS_ROUND_ROBIN):

• Round-robin. This method assigns a work queue to each WIS process alphabetically, cycling around until all work queues are assigned. For example, if a system has 5 WIS processes and 20 work queues A to O then:
— queues A, F, K are allocated to WIS process 1,
— queues B, G, L are allocated to WIS process 2,
— queues C, H, M are allocated to WIS process 3, etc.

The round-robin method takes no account of queue size. It is best used when the messages are fairly evenly distributed between the majority of queues and user access is also evenly spread.

• On-demand. This method assigns work queues to WIS processes based on cost. All work queues have a weighting (determined by the WQS_QUEUE_WEIGHTING parameter) that determines the cost of the work queue to the WIS process. Queues are assigned to the WIS process with the lowest overall cost. The more work queues that are allocated to a WIS process, the higher the cost of the WIS process. So fewer new work queues are allocated to it. The cost calculation is as follows:

cost = wicount + (WQS_QUEUE_WEIGHTING * qcount)

where:

— wicount is the number of work items the WIS process is currently processing.
— qcount is the number of work queues the WIS process is currently processing.

The number of items in a work queue is taken from data that has been persisted to the wqs_index database table. If, for example, a new queue has been added to iProcess Engine after it has been started, it means the allocation of the work queues may not reflect the actual count of work items in the work queue. To overcome this, restart iProcess Engine. This results in the work queues being re-allocated according to the latest work item count.

To control how work queues are allocated to WIS processes, you can adjust the WQS_QUEUE_WEIGHTING parameter. This parameter changes the cost of a work queue to a WIS process. For example, the larger the value, the more that the number of work queues rather than the number of work items in the work queues determines whether a work queue is allocated to a WIS process. Therefore, if you have lots of work queues with an even amount of work items in each, you may want to increase the value of the WQS_QUEUE_WEIGHTING parameter. If you only have a few work queues that contain large amounts of work items, you may want to lower the value.

The effect of the on-demand assignment is that work queues are distributed across WIS processes based on their cost, so a more even distribution of work queues is achieved.

However, there are two additional methods you can use to customize the assignment process to better reflect your system requirements, and so optimize performance.

The following sections describe these methods.

Using Different WIS Processes to Handle User and Group Queues

User queues and group queues frequently have different characteristics, in terms of the amount of load they carry.

For example, if group queues are far more active than user queues on your system, you may want to give them higher priority for WIS process allocation.

You can do this by specifying the WQS_WIS_USER_COUNT process attribute for the WQS process. This attribute defines the number of WIS processes that should be dedicated to handling user queues and group queues respectively (either as a fixed number or as a percentage of the available processes). See WQS_WIS_USER_COUNT for more information.

Assigning a Queue Explicitly to a WIS Process

If you have certain queues that are very large or very busy, you may find it useful to dedicate specific WIS processes to handling only those queues (leaving the remaining queues to be dynamically assigned to the remaining WIS processes).

To dedicate a specific WIS process to handling a specific queue:

1. Start the Process Administrator, and then start the User Manager. (See “Using TIBCO iProcess Administrator” in TIBCO iProcess Workspace (Windows) Manager's Guide for more information.)
2. To make it possible to allocate queues to specific WIS processes, define a new attribute called SW_WISINST. This should have a Type of Numeric, with a Decimal value of 0.

See “Adding a New Attribute” in TIBCO iProcess Workspace (Windows) Manager's Guide for more information.

3. To assign a queue to a specific WIS process, assign the WIS instance number that you want the queue to use as the value of the SW_WISINST attribute for that queue. (You can use the swadm show_processes command to list the available WIS instances - see Show Server Processes.)

See “Setting User Values for an Attribute” in TIBCO iProcess Workspace (Windows) Manager's Guide for more information.

4. Save your changes, exit from User Manager, and perform a MoveSysInfo event to register your changes on iProcess Engine.

See “Moving System Information” in TIBCO iProcess Workspace (Windows) Manager's Guide for more information.

5. If the queue is already in use (and therefore already allocated to a WIS process), you will need to stop and restart iProcess Engine before the change takes effect.

Once a WIS process has been dedicated to handling a specific queue or queues, it will handle only those queues. It is no longer available for dynamic queue allocation.

There is one exception to this: if all the available WIS processes are dedicated to handling specific queues, and a new queue is added, the queues are no longer treated as dedicated. This means that:

• the new queue will be dynamically assigned to the appropriate WIS process, according to the current dynamic allocation rules. All dedicated WIS processes are considered to be available to handle the queue. See Using Different WIS Processes to Handle User and Group Queues.
• the dedicated WIS processes continue to handle their assigned queues (but they may also have to handle the newly assigned queue as well).

An Example of How to Use These Assignment Methods

By using the methods described above, you can configure your system to operate more efficiently under load. For example, consider a system that has 6 WIS processes (WIS 1-6), 8 group queues (GQ1-8), and 500 users (UQ1-500). Queue characteristics are:

• GQ1 has 100K items and is a holding queue (sometimes searched).
• GQ2 has 50K items and is the most active queue.
• GQ3-8 are all fairly busy with up 10K items in each.
• User queues are not used extensively.

The system is now configured as follows:

• GQ1 is assigned to WIS 1.
• GQ2 is assigned to WIS 2.
• WQS_WIS_USER_COUNT is set to 2

This means that:

• The two biggest queues, GQ1 and GQ2, are each handled by their own dedicated WIS process, WIS 1 and WIS 2.
• The remaining 6 group queues, GQ3 to GQ8, are handled by 2 of the 4 remaining WIS processes. The queues are dynamically assigned to WIS processes.
• The remaining 2 WIS processes handle the 500 user queues. The queues are dynamically assigned to WIS processes.