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Resource Models

The Resource Models define the policy for allocating computational resources such as cpu_quota and mem_limit within containers.

Each resource model has max_cu and max_mu values, representing the maximum computing and memory units that the VirtualInstance can have.

There are three types of resource models in Fogbed: EdgeResourceModel, FogResourceModel and CloudResourceModel.

EdgeResourceModel

The Edge resource model follows a fixed limit strategy. If a container requests resources, and all of them have already been allocated, an exception is raised to alert that no more resources can be allocated for new containers. 

from fogbed import (
    FogbedExperiment, Container, Resources, EdgeResourceModel
)
exp  = FogbedExperiment()

edge_model = EdgeResourceModel(max_cu=2, max_mu=256)
edge = exp.add_virtual_instance('edge',  edge_model)

exp.add_docker(Container('d1', resources=Resources.SMALL), datacenter=edge)
exp.add_docker(Container('d2', resources=Resources.SMALL), datacenter=edge)
exp.add_docker(Container('d3', resources=Resources.SMALL), datacenter=edge)


d3: Allocation of container was blocked by resource model.

CloudResourceModel and FogResourceModel

The Fog and Cloud resource models are identical, employing an over-provisioning strategy. If a container requests HardwareResources, and all of the resources of the VirtualInstance have already been allocated to other containers, the new container starts regardless. Subsequently, the CPU time and memory limit for each container is recalculated. 

from fogbed import (
    FogbedExperiment, Container, Resources, CloudResourceModel
)
exp  = FogbedExperiment()

cloud_model = CloudResourceModel(max_cu=2, max_mu=256)
cloud = exp.add_virtual_instance('cloud',  cloud_model)

exp.add_docker(Container('d1', resources=Resources.TINY),   datacenter=cloud)
exp.add_docker(Container('d2', resources=Resources.SMALL),  datacenter=cloud)
exp.add_docker(Container('d3', resources=Resources.SMALL),  datacenter=cloud)
exp.add_docker(Container('d4', resources=Resources.MEDIUM), datacenter=cloud)

print(cloud)


[cloud]
Container(name=d1, cpu_quota=76923,  cpu_period=1000000)
Container(name=d2, cpu_quota=153846, cpu_period=1000000)
Container(name=d3, cpu_quota=153846, cpu_period=1000000)
Container(name=d4, cpu_quota=615384, cpu_period=1000000)

Predefined Resources

Below is the list of the predefined HardwareResources: 

from fogbed import Resources

>>> Resources.TINY
'HardwareResources(cu=0.5,  mu=32)'

>>> Resources.SMALL
'HardwareResources(cu=1.0,  mu=128)'

>>> Resources.MEDIUM
'HardwareResources(cu=4.0,  mu=256)'

>>> Resources.LARGE
'HardwareResources(cu=8.0,  mu=512)'

>>> Resources.XLARGE
'HardwareResources(cu=16.0, mu=1024)'