Overview

A cloud service is an abstraction of a compute service that corresponds to a cloud platform that provides access to virtualized compute resources, i.e., virtual machines (VMs). The cloud service provides all necessary functions to manage VMs (create, suspend/resume, shutdown). Jobs are never submitted directly to a cloud service. Instead, a VM instance behaves as a bare-metal service, to which jobs can be submitted.

The main difference between a cloud service and a virtualized cluster service is that the latter does expose the underlying physical infrastructure (e.g., it is possible to instantiate a VM on a particular physical host, or to migrate a VM between two particular physical hosts).

Creating a cloud compute service

In WRENCH, a cloud service is defined by the wrench::CloudComputeService class. An instantiation of a cloud 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 are available to the cloud service);
A mount point (corresponding to a disk attached to the host) for the scratch space, i.e., storage local to the cloud service (used to store workflow files, as needed, during job executions); and
Maps (std::map) of configurable properties (wrench::CloudComputeServiceProperty) and configurable message payloads (wrench::CloudComputeServiceMessagePayload).

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

auto cloud_cs = simulation.add(
          new wrench::CloudComputeService("cloud_gateway", {"host1", "host2", "host3", "host4"}, "/scratch/",
                                   {{wrench::CloudServiceProperty::VM_BOOT_OVERHEAD_IN_SECONDS, "10"}},
                                   {{wrench::BareMetalComputeServiceMessagePayload::RESOURCE_DESCRIPTION_ANSWER_MESSAGE_PAYLOAD, 1024}}));

See the documentation of wrench::CloudComputeServiceProperty and wrench::CloudComputeServiceMessagePayload for all possible configuration options.

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