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class %SYSTEM.WorkMgr extends %Library.SystemBase

This class provides an interface to the work queue manager code that allows work to be distributed to multiple processes in order to improve performance. In order to use this you need to divide the work up into units that can be processed independently then you initialize the worker jobs, then queue each unit of work and finally you wait for the work to be completed. The units of work can output to the current device which will be buffered up and output to the main job's device when that unit of work is signalled as complete. Also all units of work by default are expected to return a %Status value so it can indicate errors, these are displayed and returned by the WaitForComplete() method.

A typical calling sequence is:

  Set queue=$system.WorkMgr.Initialize("/multicompile=1",.sc) If $$$ISERR(sc) ; Report Error
  For i=1:1:100 {
  	Set sc=queue.Queue("##class(MyClass).ClassMethod",i) If $$$ISERR(sc) ; Report Error
  Set sc=queue.WaitForComplete() If $$$ISERR(sc) ; Report Error
The call to Initialize() will allocate some worker jobs from the pool to the work group you are creating, if there are not enough worker jobs in the pool then a daemon process will start additional worker automatically. The number of worker jobs we start determined by the work queue manager based on current machine load and characteristics of the CPU the machine is running on. If '/multicompile=0' then we will not use any worker jobs at all and will do all the processing in the current job in the WaitForComplete() call.

Then you call Queue() to queue a unit of work to be completed, this takes either a class method call, or a '$$func^rtn' reference and then any arguments you need to pass to this function. As soon as the first Queue() is called a worker will start processing this item of work. It is important to make sure that all the units of work are totally independent and they do not rely on other work units. You can not rely on the order in which the units of work are processed. If the units may be changing a common global you will need to add locking to ensure one worker can not change a global while another worker is in the middle of reading this global. When a unit of work is queued the current security context is stored so when the work is run it will use the current security context. Note that the worker jobs are started by the super server and so will run as the operating system user that the super server process is setup to use, this may be different to your current logged in operating system user.

Finally you call WaitForComplete() to wait for all the units of work to be complete, display any output each unit produced and report any errors reported from the work units. The WaitForComplete() will use the qualifiers provided in the Initialize().

Worker jobs are owned by the master process while they are performing work in this group, so when the master exits the worker jobs will be released immediately. When the object returned by Initialize is destroyed this will remove all work associated with this group automatically, and release any workers.

Note that the work queued should not use exclusive news, kills or unlocks as this will interfere with the framework. Also if you use process private globals to store data during the processing note that as multiple Cache jobs will be processing each chunk you can not rely on accessing these from the master process (or even from another chunk). The size of each chunk should be on the order of thousands of lines of COS code to ensure the overhead of the framework is not a significant factor, also rather than a few very large chunks (e.g. 4 big chunks) if possible it is better to have a fairly large number (100 say) of chunks as this allows us to scale with CPU cores. Worker jobs once started will remain until they time out given a long enough period of inactivity.

Property Inventory

Method Inventory


property NumActiveWorkers as %Integer [ Calculated ];
Number of active workers attached to this group. If the system is at the limit then we limit the number of worker jobs so you may need to wait for existing worker jobs to become free in order to attach to your work group.
property NumWorkers as %Integer;
After the work group is created the number of workers allocated to this group. Note this is the number of jobs we requested, not the number actively working for this group at this moment. The active number is NumActiveWorkers.


method Clear(timeout As %Integer = 0) as %Status
Clear any existing work from this work queue, it does this by removing the queue and creating a new one. The timeout is not used.
classmethod DefaultNumWorkers() as %Integer
Return the default number of worker jobs we will use if no specific number is specified
classmethod Flush() as %Status
Called from a worker job to flush any output produced so far to the master process. Without this all output from a worker job is buffered until this unit of work is complete and only then is it displayed in the master process.
method Free() as %Status
Free any workers associated with this group to put them back into general pool. You can do this after you have queued all the work.
classmethod Help(method As %String = "") as %String
Write out a list of the methods of this object to the console. Pass the method name as an argument to see the full description for this item.
classmethod Initialize(qspec As %String = "", ByRef sc As %Status, numberjobs As %Integer) as WorkMgr
Initialize the worker jobs so they are ready to start accepting work items. In the qspec that is passed you can determine if you want output with the 'd' flag and if you wish to disable multiple jobs and process the work in this master process with '/multicompile=0'. This returns an instance of the worker queue manager which you can then queue work against. If you wish to specify how many workers you require then pass the numberjobs equal to the number you require. You may also pass the number in the /multicompile=NUM as long as NUM is greater than 1 or for 1 worker specify '-1' i.e. /multicompile=-1.
classmethod IsWorkerJob() as %Boolean
If you do not pass in any arguments returns true/false based on if the current process is a worker job or not.
method NumActiveWorkersGet() as %Integer
method NumberWorkers() as %Integer
After the Initialize() is called this will return the current number of worker jobs that are active for this group.
method Pause() as %Status
Pause any work in this work queue, this stops any workers from picking up additional items from this specific queue, but leaves the work itself so you can call Resume().
method Queue(work As %String, args... As %String) as %Status
Queues a specific unit of work, you pass the entry point to call in 'work' argument. This can be either '##class(Classname).ClassMethod' or '$$entry^rtn' and it is expected to return a %Status code on completion. If you want to call a function that does not return any value on completion then prepend the class syntax with '=' such as '=##class(Classname).ClassMethod' or for calling a function do not include the '$$' for example 'entry^rtn'. The item being called may also throw exceptions in order to indicate an error happened which is trapped and converted to a %Status value to be returned in the master process. You can also pass additional arguments including arrays by reference. Note that the size of the data passed in these arguments should be kept relatively small, if there is a large amount of information that needs to be passed then put this in a global. The security context of the caller is also recorded when this function is called so it can be used when the work is executed.
method QueueCallback(work As %String, callback As %String, args... As %String) as %Status
Similar to Queue() except you can also pass in a 'callback' which is a function or class method that is called in the master process when this unit of work is complete. This function is called with the same arguments the original 'work' is called with so it knows which unit of work is complete. Also the callback function can access the '%job' public variable which is the $job of the process which really did the work, the '%status' public variable which is the %Status return code from the work unit this is the callback for and '%workqueue' public variable which is the oref of the work queue instance. If using the Wait() to wait for the work to be completed the callback can signal that it should return to the caller rather than waiting for more events by setting the public variable '%exit' to 1.
method Resume() as %Status
Resume any work in this work queue which was paused with a call to Pause().
method Setup(work As %String, args... As %String) as %Status
If this queue needs some setup work before we process the first item in this queue or if switching from processing items in another queue to one in this queue then specify the function to call here. The arguments are the same as for Queue(). This must be called before you queue work.
method TearDown(work As %String, args... As %String) as %Status
If this queue needs some work done to restore a process to the previous state before we process the first item in another queue when switching from processing items in this queue then specify the function to call here. The arguments are the same as for Queue(). This must be called before you queue work.
method Wait(qspec As %String, ByRef AtEnd As %Boolean) as %Status
After work has been queued this will wait for a signal from a callback to exit back to the caller. This is done by in the callback queued with QueueCallback() setting the public variable '%exit' to 1. This method returns AtEnd to show if all the work is complete or if there are still items outstanding. Note that in the function/method called in the QueueCallback() callback you can reference the public variable '%workqueue' which is the oref of the instance of the work queue class in order to queue additional work.
method WaitForComplete(qspec As %String, errorlog As %String) as %Status
After work has been queued this will wait for all the workers to complete. It will display any output the work writes to the current device and it will also combine all the %Status codes that the units of work report and return this combined %Status. If there are no workers then this will execute all the work in this main job during this phase. When this returns all the work queued up to this point has been completed. Also this is the phase that will run the QueueCallback() callbacks as the workers jobs report that various units are complete. Note that in the function/method called in the QueueCallback() callback you can reference the public variable '%workqueue' which is the oref of the instance of the work queue class in order to queue additional work.

Inherited Members

Inherited Methods


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