8. Using Local and Remote HPC Resources

8.1. Introduction

RADICAL-Pilot allows you to launch a ComputePilot allocating a large number of cores on a remote HPC cluster. The ComputePilot is then used to run multiple ComputeUnits with small core-counts. This separates resource allocation and management from resource usage, and avoids HPC cluster queue policies and waiting times which can significantly reduce the total time to completion of your application.

If you want to use a remote HPC resource (in this example a cluster named “Archer”, located at EPSRC, UK) you have to define it in the ComputePilotDescription like this:

pdesc = radical.pilot.ComputePilotDescription()
pdesc.resource = "epsrc.archer"
pdesc.project  = "e1234"
pdesc.runtime  = 60
pdesc.cores    = 128

Using a resource key other than “local.localhost” implicitly tells RADICAL-Pilot that it is targeting a remote resource. RADICAL-Pilot is using the SSH/GSISSH (and SFTP/GSISFTP) protocols to communicate with remote resources. The next section, Configuring SSH Access provides some details about SSH set-up. Pre-Configured Resources lists the resource keys that are already defined and ready to be used in RADICAL-Pilot.

8.2. Configuring SSH Access

If you can manually SSH into the target resource, RADICAL-Pilot can do the same. While RADICAl-Pilot supports username and password authentication, it is highly-advisable to set-up password-less ssh keys for the resource you want to use. If you are not familiar with how to setup password-less ssh keys, check out this link.

All SSH-specific informations, like remote usernames, passwords, and keyfiles, are set in a Context object. For example, if you want to tell RADICAL-Pilot your user-id on the remote resource, use the following construct:

session = radical.pilot.Session()

c = radical.pilot.Context('ssh')
c.user_id = "tg802352"
session.add_context(c)

Note

Tip: You can create an empty file called .hushlogin in your home directory to turn off the system messages you see on your screen at every login. This can help if you encounter random connection problems with RADICAL-Pilot.

8.3. Pre-Configured Resources

Resource configurations are a set of key/value dictionaries with details of a remote resource like queuing-, file-system-, and environment-. Once a configuration file is available for a given resource, a user chooses that pre-configured resource in her code like this:

pdesc = radical.pilot.ComputePilotDescription()
pdesc.resource   = "epsrc.archer"
pdesc.project    = "e1234"
pdesc.runtime    = 60
pdesc.cores      = 128
pdesc.queue      = "large"

The RADICAL-Pilot developer team maintains a growing set of resource configuration files. Several of the settings included there can be overridden in the ComputePilotDescription object. For example, the snipped above replaces the default queue standard with the queue large. For a list of supported configurations, see List of Pre-Configured Resources - those resource files live under radical/pilot/configs/.

8.4. Writing a Custom Resource Configuration File

If you want to use RADICAL-Pilot with a resource that is not in any of the provided resource configuration files, you can write your own, and drop it in $HOME/.radical/pilot/configs/<your_resource_configuration_file_name>.json.

Note

Be advised that you may need specific knowledge about the target resource to do so. Also, while RADICAL-Pilot can handle very different types of systems and batch system, it may run into trouble on specific configurations or software versions we did not encounter before. If you run into trouble using a resource not in our list of officially supported ones, please drop us a note on the RADICAL-Pilot users mailing list.

A configuration file has to be valid JSON. The structure is as follows:

# filename: lrz.json
{
    "supermuc":
    {
        "description"                 : "The SuperMUC petascale HPC cluster at LRZ.",
        "notes"                       : "Access only from registered IP addresses.",
        "schemas"                     : ["gsissh", "ssh"],
        "ssh"                         :
        {
            "job_manager_endpoint"    : "loadl+ssh://supermuc.lrz.de/",
            "filesystem_endpoint"     : "sftp://supermuc.lrz.de/"
        },
        "gsissh"                      :
        {
            "job_manager_endpoint"    : "loadl+gsissh://supermuc.lrz.de:2222/",
            "filesystem_endpoint"     : "gsisftp://supermuc.lrz.de:2222/"
        },
        "default_queue"               : "test",
        "lrms"                        : "LOADL",
        "task_launch_method"          : "SSH",
        "mpi_launch_method"           : "MPIEXEC",
        "forward_tunnel_endpoint"     : "login03",
        "global_virtenv"              : "/home/hpc/pr87be/di29sut/pilotve",
        "pre_bootstrap_1"             : ["source /etc/profile",
                                         "source /etc/profile.d/modules.sh",
                                         "module load python/2.7.6",
                                         "module unload mpi.ibm", "module load mpi.intel",
                                         "source /home/hpc/pr87be/di29sut/pilotve/bin/activate"
                                        ],
        "valid_roots"                 : ["/home", "/gpfs/work", "/gpfs/scratch"],
        "agent_type"                  : "multicore",
        "agent_scheduler"             : "CONTINUOUS",
        "agent_spawner"               : "POPEN",
        "pilot_agent"                 : "radical-pilot-agent-multicore.py"
    },
    "ANOTHER_KEY_NAME":
    {
        ...
    }
}

The name of your file (here lrz.json) together with the name of the resource (supermuc) form the resource key which is used in the class:ComputePilotDescription resource attribute (lrz.supermuc).

All fields are mandatory, unless indicated otherwise below.

  • description: a human readable description of the resource.
  • notes: information needed to form valid pilot descriptions, such as what parameter are required, etc.
  • schemas: allowed values for the access_schema parameter of the pilot description. The first schema in the list is used by default. For each schema, a subsection is needed which specifies job_manager_endpoint and filesystem_endpoint.
  • job_manager_endpoint: access url for pilot submission (interpreted by SAGA).
  • filesystem_endpoint: access url for file staging (interpreted by SAGA).
  • default_queue: queue to use for pilot submission (optional).
  • lrms: type of job management system. Valid values are: LOADL, LSF, PBSPRO, SGE, SLURM, TORQUE, FORK.
  • task_launch_method: type of compute node access, required for non-MPI units. Valid values are: SSH,``APRUN`` or LOCAL.
  • mpi_launch_method: type of MPI support, required for MPI units. Valid values are: MPIRUN, MPIEXEC, APRUN, IBRUN or POE.
  • python_interpreter: path to python (optional).
  • pre_bootstrap_1: list of commands to execute for initialization of main agent (optional).
  • pre_bootstrap_2: list of commands to execute for initialization of sub-agent (optional).
  • valid_roots: list of shared file system roots (optional). Note: pilot sandboxes must lie under these roots.
  • pilot_agent: type of pilot agent to use. Currently: radical-pilot-agent-multicore.py.
  • forward_tunnel_endpoint: name of the host which can be used to create ssh tunnels from the compute nodes to the outside world (optional).

Several configuration files are part of the RADICAL-Pilot installation, and live under radical/pilot/configs/.

8.5. Customizing Resource Configurations Programatically

The set of resource configurations available to the RADICAL-Pilot session is accessible programmatically. The example below changes the default_queue for the epsrc.archer resource.

import radical.pilot as rp
import pprint

RESOURCE = 'epsrc.archer'

# get a pre-installed resource configuration
session = rp.Session()
cfg = session.get_resource_config(RESOURCE)
pprint.pprint (cfg)

# create a new config based on the old one, and set a different launch method
new_cfg = rp.ResourceConfig(RESOURCE, cfg)
new_cfg.default_queue = 'royal_treatment'

# now add the entry back.  As we did not change the config name, this will
# replace the original configuration.  A completely new configuration would
# need a unique label.
session.add_resource_config(new_cfg)
pprint.pprint (session.get_resource_config(RESOURCE))