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Detaching and Attaching a Work Queue

Typically, when using the Work Queue Manager, you initialize a set of worker jobs, queue work items, and then wait for the worker jobs to complete the work items. However, you may encounter situations where worker jobs are taking longer than expected to complete work items or you cannot dedicate a single process to waiting. Consequently, the Work Queue Manager enables you to detach a work queue from a process and subsequently attach the work queue to the same process or to a different process.

For example, suppose that queue references a work queue that you initialized. Also suppose that you added several work items to the work queue. Before calling the Wait() or WaitForComplete() to determine the status of the work being processed, you could employ the following methods.

Detaching a Work Queue

method Detach(ByRef token As %String, timeout As %Integer=86400) as Status

Detaches the work queue object from the object reference that you created when you initialized the work queue. The Detach() method enables any work in progress to continue and preserves the current state of the work queue.

The token argument represents a secure token that you can use to subsequently attach the work queue to another process. The timeout argument is optional and indicates the amount of time in seconds that the system retains the detached work queue object. After the timeout period has elapsed, the system removes any worker jobs and information associated with the work queue. The default value of timeout is one day.

After you call the Detach() method, most calls on the detached object reference return errors. However, the NumActiveWorkers() and NumWorkers() methods return -1.

Attaching a Work Queue

method Attach(token, ByRef sc As %Status) as WorkMgr

Attaches a new object reference to a previously detached work queue object if the work queue object is still in memory. The Attach() method returns a new instance of the Work Queue Manager associated with the work queue. You can subsequently call methods on the work queue. For example, you can call the Wait() method with a timeout value of 0 to determine whether the queue had completed any work items before being detached.

The token argument represents the secure token returned by the Detach() method that you previously called on the work queue.


For example, you could detach and then attach a work queue as follows:

Set sc=queue.Detach(.token,60)
If $$$ISERR(sc) {
       Return sc
Set queue=$system.WorkMgr.Attach(token,.sc)
If $$$ISERR(sc) {
       Return sc

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