--- layout: documentation title: DDI-API --- {% include base.html %} This API is based on HTTP standards and based on a polling mechanism. The _hawkbit_ [update server](https://github.com/eclipse/hawkbit) provides REST resources which are consumed by the device to retrieve software update tasks. Note: in DDI the target is identified using a **controllerId**. Controller is used as a term for the actual service/client on the device. That allows users to have in some cases even multiple clients on the same target for different tasks, e.g. Firmware update and App management. # State Machine Mapping For historical reasons the DDI has a different state machine and status messages than the [Target State Machine](../architecture/targetstate.html) of the _hawkBit_ update server. This is kept in order to ensure that _DDI_ stays compatible for devices out there in the field. A future version "2" of _DDI_ might change that. _DDI_ also defines more states than the update server, e.g. multiple DDI states are currently mapped by the _DDI_ implementation to _RUNNING_ state. It is possible that in the future _hawkBit_ will fully leverage these additional states. The _DDI_ API allows the device to provide the following feedback messages: DDI `status.execution` type | handling by update server | Mapped ActionStatus type --------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------- CANCELED | This is send by the target as confirmation of a cancelation request by the update server. | CANCELED REJECTED | This is send by the target in case an update of a cancelation is rejected, i.e. cannot be fulfilled at this point in time. Note: the target should send a CLOSED->ERROR if it believes it will not be able to proceed the action at all. | WARNING CLOSED | Target completes the action either with `status.result.finished` SUCCESS or FAILURE as result. Note: DDI defines also a status NONE which will not be interpreted by the update server and handled like SUCCESS. | ERROR (DDI FAILURE) or FINISHED (DDI SUCCESS or NONE) PROCEEDING | This can be used by the target to inform that it is working on the action. | RUNNING SCHEDULED | This can be used by the target to inform that it scheduled on the action. | RUNNING RESUMED | This can be used by the target to inform that it continued to work on the action. | RUNNING # Resource Overview