Lifecycle of a work item

The Status field of a work item records the current state of its lifecycle. The work queue framework manages this field and the lifecycle of work items for your writer and workers. The following diagram illustrates the lifecycle.

A work item begins life after the writer selects the units of work for a batch and returns an iterator for the collection. The framework then creates work items that reference the units of work for a batch. The initial state of a work item is available. At the time the framework checks out a quota of work items for a worker, the state of the work items becomes checkedout. The framework then hands the quota of work items to the worker one at a time. After a worker finishes processing a work item successfully, the framework deletes it from the work queue and updates the statistics in the process history for the batch.

Returning work items to the work queue

Sometimes a worker cannot finish processing a work item successfully. For example, a network resource may be temporarily unavailable. Or, a concurrent data change exception (CDCE) can occur if multiple workers simultaneously update common entity data in the domain graphs of two separate units of work. Whenever errors occur, the worker throws an exception to return the work item to the work queue as available again.

Whenever a worker returns a work item to the work queue, PolicyCenter increments the Attempts property on the work item. If the value of Attempts remains below the retry limit for the worker, the state of the work item remains available. The work item is subsequently checked out in a quota for the same or another worker. If the temporary error condition clears, the next worker completes it successfully and PolicyCenter removes the work item from the work queue.

Work items that fail

Whenever a worker returns a checked out work item and the Attempts property exceeds the work item retry limit, the state of the work item becomes failed. Failed work items end their lifecycle in this state. Workers ignore items with a status of failed and no longer attempt to process them. Someone must determine the reason for the failure of a work item and take corrective action. They can then remove the failed work item from the work queue.