Overview

A virtualized cluster service is an abstraction of a compute service that corresponds to a platform of physical resources on which Virtual Machine (VM) instances can be created. A virtualized cluster service is very similar to a a cloud service, the only difference being that the former exposes the underlying physical resources, while the latter does not. More specifically, it is possible to instantiate a VM on a particular physical host, and to migrate a VM between two physical hosts.

Creating a virtualized cluster compute service

In WRENCH, a virtualized cluster service is defined by the wrench::VirtualizedClusterComputeService class. An instantiation of a virtualized cluster service requires the following parameters:

The name of a host on which to start the service;
A list (std::vector) of hostnames (all cores and all RAM of each host is available to the virtualized cluster service);
A mount point (corresponding to a disk attached to the host) for the scratch space, i.e., storage local to the virtualized cluster service (used to store workflow files, as needed, during job executions); and
Maps (std::map) of configurable properties (wrench::VirtualizedClusterComputeServiceProperty) and configurable message payloads (wrench::VirtualizedClusterComputeServiceMessagePayload).

The example below creates an instance of a virtualized cluster service that runs on host vc_gateway, provides access to 4 execution hosts, and has a scratch space on the disk mounted at path /scratch at host vc_gateway. Furthermore, the VM boot time is configured to be 10 second, and the message with which the service answers resource description requests is configured to be 1KiB:

auto virtualized_cluster_cs = simulation.add(
          new wrench::VirtualizedClusterComputeService("vc_gateway", {"host1", "host2", "host3", "host4"}, 
                                                "/scratch/", {{wrench::VirtualClusterComputeServiceProperty::VM_BOOT_OVERHEAD_IN_SECONDS, "10"}}, {{wrench::VirtualClusterComputeServiceMessagePayload::RESOURCE_DESCRIPTION_ANSWER_MESSAGE_PAYLOAD, 1024}}));

See the documentation of wrench::VirtualizedClusterComputeServiceProperty and wrench::VirtualizedClusterComputeServiceMessagePayload for all possible configuration options.

Also see the simulators in the examples/basic-examples/virtualized-cluster-*/ directories, which use virtualized cluster services.