Handling Status Updates

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This page collects information how to enable a status query for algorithms running the the 52°North WPS.

Specification Features

WPS 1.0.0

In the WPS 1.0.0 specification, the following aspects are used for status handling. Status elemeent is defined to carry information about the execution state of a process.

Process Description

"The statusSupported parameter is used to support asynchronous requests via a type of polling. [...]"

For details see section 9.3.1.

Execute Response

"The status element [..] has five possible subelements (choice): ProcessAccepted, ProcessStarted, ProcessPaused, ProcessFailed and ProcessSucceeded [..]".

See section 10.3.1 for details.

Inf short, you can add messages to the different status elements, e.g. <wps:ProcessAcceptedProcess>Accepted</wps:ProcessAccepted>, or provide numerical status information in the percentCompleted attribute like this: <wps:ProcessStarted percentCompleted="42" />.

Alternatively, looking at the schema for Execute responses: The Status element cannot be extended, but the ProcessOutputs can hold any content and has the following description: "List of values of the Process output parameters. [..] If the process has not finished executing, the implementer can choose to include whatever final results are ready at the time the Execute response is provided.[..]"

So from the specification perspective, one could also provide extended status information there as an intermediate result.

WPS 2.0

to be updated once the WPS 2.0 specification is completed.

Processing Backends

Java Algorithm

If you use the 52°North WPS and let your process implement ISubject, you can update the status of a running process (i.e. wps:ProcessStarteddddd element).

• Integer values will be added to the percentCompleted attribute, e.g. <wps:ProcessStarted percentCompleted="21"/>
• String messages will be added to the element, e.g: <wps:ProcessStarted>Executed step 1 of 3</wps:ProcessStarted>.

The AbstractObservableAlgorithm shows how the same class implements IAlgorithm and ISubject.

check if the statusSupported for process descriptions is supported.

R Algorithm

tbd.