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Pay-per-Use licensing model counts the use of credits associated with licenses. User buys one or more licenses for a certain total amount of credits, credits are written off according to the reported use. At any time user can get more credits by buying additional licenses.

The credits may be tied to a various metrics such as CPU load, network bandwidth utilization, or anything else related to the nature of your application.

The billing is accordingly tied to the chosen model, which can be for instance:

  • Time based: billing on the duration of use
  • Count based: billing on the number of uses
  • Volume based: billing on the amount of resource use

In either case, NetLicensing keeps track of credits by a simple integer counters, stored in quantity and usedQuantity properties of each license. You decide what actual metric to associate with the credits.

For better adapting to various scenarios, Pay-per-Use supports two modes of operation: pre-payment and post-payment. The mode is decided by arguments passed to the validate call, see the validation section below for details.

License Templates

To use this licensing model you must define one or more license templates of type QUANTITY, each specifying the credits amount (via quantity property) and a purchase price. Multiple license templates allow to configure discounts, e.g.:

  • 10 credits for 5 EUR
  • 100 credits for 45 EUR
  • 1000 credits for 400 EUR

Additional properties specific to the QUANTITY license templates:

  • Integer quantity (required) - specifies credits amount, which is assigned by default to the licenses created off this template.


Additional properties specific to the QUANTITY licenses:

  • Integer quantity (required) - specifies the credits amount, provided by this license. Normally it is copied from the corresponding property of the license template, but can be changed later for each license individually. When multiple QUANTITY licenses purchased, the total amount of credits is the sum of quantity of all active licenses.
  • Integer usedQuantity (optional) - specifies the amount of used credits. When not present, it is equivalent to usedQuantity=0. This property is updated automatically according to the parameters passed to the validate call (see below). usedQuantity equal to quantity means all credits of this license are used up.


On validation, this licensing model uses the following validate parameters:

  • productModuleNumber=<productModuleNumber> - specifies the product module, that uses Pay-per-Use licensing model
  • usedQuantity=<non-negative integer> - specifies how many credits has been used by the application since previous validate call (post-payment mode). In case more credits were used than the remaining credits, remaining credits get negative.
  • reserveQuantity=<non-negative integer> - specifies the credits amount that the application attempts to reserve for use until next validate call (pre-payment mode). It is not possible to reserve more than the remaining credits.

usedQuantity and reserveQuantity parameters are mutually exclusive - use only one of them depending on the mode you need. If both usedQuantity and reserveQuantity parameters to validate are omitted, it is equivalent to usedQuantity=0. However, if you need to call validate just for reading-out the remaining credits, it is suggested to pass usedQuantity=0 explicitly. This helps better traceability of the call by explicit declaration of intent.

Validation returns values:

  • Boolean valid - true if the sum of quantity of all active licenses (given credits) is bigger than the sum of usedQuantity of these licenses (used credits).
  • Integer remainingQuantity - the amount of credits still available for use. It is the difference between the sum of quantity and the sum of usedQuantity of all active licenses.

Post-payment mode

This mode is activated by passing usedQuantity validate parameter. Provided value is written off from the remaining credits. valid=true in the response indicates that some credits still remain after writing off passed value. The application should take care that the remainingQuantity returned by the previous validate call is not exceeded, however in this mode overdraft is allowed, in which case remainingQuantity in the response will get negative. When all remaining credits are used up (validate has returned valid=false), the application would normally direct the user to the appropriate step for getting more credits, or disable corresponding functionality.

Validation response examples:

 Some credits still remain
 All remaining credits are used up by this validate call
 Attempt to use more than the remaining credits

Pre-payment mode

This mode is activated by passing reserveQuantity validate parameter. If provided value is less than or equal to the remaining credits, it is written off from the remaining credits, and valid=true returned in the response. In case provided value exceeds remaining credits, remaining credits stay unchanged, and valid=false returned in the response.

Validation response examples:

 Enough credits available
 Enough remaining credits available, all are used up by this validate call
 Attempt to reserve more than the remaining credits