DRM4G Use Cases

Implemented features

Use case: Creating cloud credentials
Description	Creates the proxy certificate that will be used to access the Federated Cloud's services
Primary Actor	User
Preconditions	The DRM4G must be running on a terminal The user must have edited correctly the configuration file The user must have a valid grid certificate
Basic Flow	The user executes the command drm4g id <resource_name> init
Postconditions	A proxy valid for 7 days will have been generated
Alternate Flow	The user uses the option --lifetime to create an identity for a specific period of time

Use case: Creating VMs
Description	An active and accessible Virtual Machine (VM) will be created. It will be considered a host to whom the user can submit jobs to have executed
Primary Actor	User
Preconditions	The DRM4G must be running on a terminal The user must have edited correctly the configuration file The user must have already created his x509 certificate proxy
Basic Flow	The user executes the command drm4g resource create The program will read the configuration file For every resource defined to create VMs, it will create as many VMs as nodes were specified
Postconditions	As many VMs as nodes specified in the configuration file will have been created The VM's public IP direction will be shown Submitted jobs will also be sent to the VM
Alternate Flow	If for some reason there's a problem creating a VM, an error message is displayed The program will continue creating the rest of the specified VMs

Use case: Adding VMs
Description	Adds more VMs to those previously created
Primary Actor	User
Preconditions	User must have previously created VMs
Basic Flow	The user executes the command drm4g resource create
Postconditions	As many VMs as nodes specified in the configuration file will have been added The VM's public IP direction will be shown Submitted jobs will also be sent to the VM
Alternate Flow	If for some reason there's a problem creating a VM, an error message is displayed The program will continue creating the rest of the specified VMs

Use case: Listing VMs
Description	A list of all the accessible VMs will be displayed
Primary Actor	User
Preconditions	User must have previously created VMs
Basic Flow	User runs the commands drm4g host list
Postconditions	A list with information from every host will be shown, including from all of the active VMs created
Alternate Flow

Use case: Listing resources
Description	A list with every defined resource will be displayed. That includes the ones defined by the user and the ones created by the program for every VM created
Primary Actor	User
Preconditions	The DRM4G must be running on a terminal
Basic Flow	The user runs the command drm4g resource list --all
Postconditions	A list with information from every resource will be displayed
Alternate Flow	If there aren't any defined resources, none will appear

Use case: Sending jobs
Description	Jobs will be sent to all available hosts to be executed
Primary Actor	User
Preconditions	The DRM4G must be running on a terminal The user must have edited correctly the configuration file The user must have edited correctly a job template
Basic Flow	The user runs the command drm4g job submit path/to/job/template.job
Postconditions	The job is executed by one of the available host. This includes those defined in the configuration file with the purpose of executing jobs and VMs that may have been previously created
Alternate Flow	The user uses the option --ntasks to determine how many times he wants to have the same job executed The user uses the option --dep to define the job dependency list of the job

Use case: Destroying all VMs
Description	Regardless whether they are being used o not, every VM created by the DRM4G will be destroyed
Primary Actor	User
Preconditions	The user must have previously created VMs
Basic Flow	The user runs the command drm4g resource destroy The program will eliminate all created VMs one by one
Postconditions	There won't be any VM left
Alternate Flow	If for some reason there's a problem destroying a VM, an error message is displayed The program will continue destroying the rest of the VMs

Forthcoming features

Use case: Listing VMs with IDs
Description	When running the command drm4g resource list --all, the program will detect if the resource it's listing is a VM and list its ID
Primary Actor	User
Preconditions	The user must have previously created VMs
Basic Flow	The user runs the command drm4g resource list --all If the program detects that the resource it's listing is a VM, it will add to the rest of its information it displays its VM ID.
Postconditions	A list with information from every resource will be displayed VMs' information will display its ID
Alternate Flow

Use case: Creating VMs dynamically
Description	The user will indicate in the "resources.conf" with the configuration keys "max_nodes" and "min_nodes" how many VMs he wants created
Primary Actor	User
Preconditions	There must be a resource in the configuration defined with the purpose for the creation of VMs The user must have already created his x509 certificate proxy
Basic Flow	The program checks how may VMs are already available If the total number of created VMs is the same as "min_nodes" it does nothing If the total number of created VMs is less than "min_nodes" it creates as many VMs necessary to reach "min_nodes" After "min_nodes" VMs have been created, if there are still a certain number of jobs in a pending state for a hard-coded period of time, an additional VM will be created This will go on for every cycle until either the number of VMs has reached "max_nodes" or until the number of pending jobs goes below the aforementioned limit If the number of pending jobs is below the aforementioned limit but the amount of time they have been pending is larger than several times the aforementioned limit, an additional VM will be created as long as the number of created VMs is smaller than "max_nodes"
Postconditions	As long as the billing hasn't reached it's limit, there will always be a VM available for use
Alternate Flow	If the user hasn't specified "max_nodes" or "min_nodes" "min_nodes" will be given a value of zero "max_nodes" won't be given a limit If only "min_nodes" has been specified, "max_nodes" will be given the same value If only "max_nodes" has been specified, "min_nodes" will be given a value of zero

Use case: Destroying VMs dynamically
Description	The DRM4G will check if certain parameters have been met and then will proceed to destroy the VMs
Primary Actor	DRM4G
Preconditions	There must be a resource in the configuration defined with the purpose for the creation of VMs The user must have already created his x509 certificate proxy
Basic Flow	For each VM, the DRM4G will check how many jobs it's currently running If there aren't any jobs, the VM will be given an idle state It will remain in this state until it's assigned a job If a VM stays idle for a certain amount of time, it will be destroyed If a VM has been marked to be destroyed but the user has already been charged for it, it won't be destroyed until the time it has been hired for has passed If a VM has been marked to be destroyed but a job is assigned to it, it will be given a second chance, but the the second time it gets marked it will be destroyed
Postconditions	The VMs will be correctly destroyed until the number of available VMs reaches "min_nodes"
Alternate Flow	If the user has run out of money, all VMs will be destroyed It will wait for the last paid hour to pass before destroying the VM