Request a usage slot with the given priority. PutQueue ¶Īlias of builtins.list request ( priority: int = 0, preempt: bool = True ) → ¶ Order by their priority (that means lower values are more important). Pending requests in the queue are sorted in ascending PriorityResource ( env:, capacity: int = 1 ) ¶ Number of users currently using the resource. List of Request events for the processes that are currently The env parameter is the Environment instance the Released, a pending request will be triggered. If all slots are taken, requests are enqueued. Resource with capacity of usage slots that can be requested by Whose resource users can be preempted by requests with a higher priority. Processes can define a request priority, and a PreemptiveResource Note, that releasing a resource willĪlways succeed immediately, no matter if a process is actually using a resourceīesides Resource, there is a PriorityResource, where Thus, calling request()/ release() isĮquivalent to calling put()/ get(). Resources” and releasing a resources correspondingly as “getting a process’ Requesting a resource is modelled as “putting a process’ token into the For example, a gas station with a limited number of fuel Processes request these resources to become a user and have to release them These resources can be used by a limited number of processes at a time. In use, the vehicle needs to wait until one of the users has finished refueling VehiclesĪrrive at the gas station and request to use a fuel-pump. A gas stationĬan be modelled as a resource with a limited amount of fuel-pumps. The usage right is not needed anymore it has to be released. A process needs to request the usage right to a resource. These resources can be used to limit the number of processes using themĬoncurrently. Shared resources supporting priorities and preemption.