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Installing an Open Science Pool Access Point

This document explains how to add a path for user jobs to flow from your local site out to the Open Science Pool (OSPool), which in most cases means that the jobs will have far more capacity available to run on than locally. This is useful if:

  • your local batch system frequently has many jobs waiting to run for a long time
  • you do not have a local batch system
  • you want to provide a local entry point for OSPool-bound jobs

Note that if you do not have a local batch system, consider having your users use OSG Connect, which will require less infrastructure work at your site.

Note

Flocking to OSPool resources requires some modification to user workflows. After installation, see the usage section for instructions on what your users will need to do.

Background

Every batch computing system has one or more entry points that users log on to and use to hand over their computing work to the batch system for completion. For the HTCondor batch system, we say that users log on to an Access Point (AP) (also known as a submit node or submit host) to submit their jobs to HTCondor, where the jobs wait ("are queued") until computing capacity is available to run them. In a purely local HTCondor system, there are one to a few Access Points and many computing resources.

An HTCondor Access Point can also be configured to forward excess jobs to the OSPool. This process is called flocking. If you already have an HTCondor pool, we recommend that you install this software on top of one of your existing HTCondor Access Points. This approach allows a user to submit locally and have their jobs run locally or, if the user chooses and if local capacity is unavailable, have their jobs automatically flock to the OSPool. If you do not have an HTCondor batch system, following these instructions will install the HTCondor AP software and configure it only to forward jobs to the OSPool. In other words, you do not need a whole HTCondor batch system just to have a local OSPool Access Point.

System Requirements

The hardware requirement for an OSPool Access Pool depends on several factors such as number of users, number of jobs and for example how I/O intensity of those jobs. Our minimum recommended configuration is 6 cores, 12 GB RAM and 1 TB of local disk. The hardware can be bare metal or virtual machine, but we do not recommend containers as these submit host are running many system services which can be difficult to configure in a container.

Also consider the following configuration requirements:

  • Operating system: Ensure the host has a supported operating system
  • Software repositories: Install the appropriate EPEL and OSG Yum repositories for your operating system
  • User IDs: If it does not exist already, the installation will create the Linux user ID condor.
  • Network:
    • Inbound TCP port 9618 must be open.
    • The access point must have a public IP address with both forward and reverse DNS configured.

Scheduling a Planning Consultation

Before participating in the OSPool, either as a computational capacity contributor or consumer, we ask that you contact us to set up a consultation. During this consultation, OSG staff will introduce you and your team to the OSG and develop a plan to meet your capacity contribution and/or research goals.

Initial Steps

Read the Acceptable Usage Policy

Be aware that hosting an access point comes with responsibilities, both for the administrators as well as end users of the system. The polices can be found in the Acceptable Usage Policy document.

Register your Access Point in OSG Topology

To make use of OSPool capacity, your AP must be registered in the OSG Topology system. You will need information like the hostname, and the administrative and security contacts. Follow the general registration instructions. For historical reasons, the service type is Submit Node. We also request that you tag the resources with OSPool. An example of a registration is the osg-vo.isi.edu entry

Register with COManage

The adminstrative contact from the the Topology entry needs to register with COManage. Instructions can be found here

Obtain an Authentication Token

The new Access Point will need an authentication token to authenticate to the OSPool Central Manager. Once your Access Point is registered in OSG Topology and you are registered with COManage, you can obtain a token from the OSG Token Registration page.

You will need a host with Docker to run the software used for retrieving the token. Use your COManage registered and approved identity to log into the OSG Token Registration page. Follow the instructions on the website; in the list of hosts, select the hostname of the Access Point that you registered earlier.

Save this token file; you will use it later when configuring authentication.

Installing Required Software

Flocking requires HTCondor software as well as software for reporting to the OSG accounting system. Start by setting up the EPEL and OSG YUM repositories following the Installing Yum Repositories document.

Once the Yum repositories are setup, install the osg-flock convenience RPM that installs all required packages. Example on a RHEL 9 host:

# yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-9.noarch.rpm
# yum install https://repo.opensciencegrid.org/osg/23/osg-23-el9-release-latest.rpm
# yum install osg-flock

Configuring Reporting via Gratia

Reporting to the OSG accounting system is done using the Gratia service, which consists of probes. HTCondor uses the "condor-ap" probe, which is configured in /etc/gratia/condor-ap/ProbeConfig: see this section for more details.

Configuring Authentication

Copy the token that you obtained from the authentication token step above, to the location /etc/condor/tokens.d/ospool.token on the Access Point. Ensure that there aren't any line breaks in this file (i.e., the entire token should only take up one line).

Change the ownership of the ospool.token file to condor:condor and the permissions to 0600. Verify this with ls -l /etc/condor/tokens.d/ospool.token:

# ls -l /etc/condor/tokens.d/ospool.token
-rw------- 1 condor condor 288 Nov 11 09:03 /etc/condor/tokens.d/ospool.token

You can also list the token with the condor_token_list command:

# condor_token_list 
Header: {"alg":"HS256","kid":"POOL"} Payload: {"iat":1234,"iss":"flock.opensciencegrid.org","jti":"...","scope":"condor:\/READ condor:\/ADVERTISE_SCHEDD","sub":"[email protected]"} File: /etc/condor/tokens.d/ospool.token

Managing Services

The only service which is required to be running is condor. Enable and restart the sevice:

# systemctl enable condor
# systemctl restart condor

Usage

Running jobs in the OSPool

If your users are accustomed to running jobs locally, they may encounter some significant differences when running jobs in the OSPool. Users should be aware that OSPool jobs are distributed across multiple institutions across a large geographical area. Each institution will have its own policy about the kinds of jobs that are allowed to run, and data transfer may be more complicated. The OSG Helpdesk Solutions page has information about what users should know; the Organizing and Submitting HTC Workloads Tutorial and

Policies for Using OSG Services and the OSPool are particularly relevant.

Specifying a project

OSPool Execution Points (EPs) will only run jobs that have a registered project associated with them. Users must follow the instructions for starting a project in OSG-Connect to register a project.

A project is associated with a job by adding a +ProjectName line to the user's submit file. For example:

+ProjectName = "My_Project"

The + and the double quotes are necessary. Otherwise, the job will fail to submit or it will not run in the OSPool.

Get Help

If you need help with setup or troubleshooting, see our help procedure.

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