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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 OSG, which in most cases means that the jobs will have far more resources available to run on than locally. If your local batch system frequently has many jobs waiting to run for a long time, you do not have a local batch system, or if you simply want to provide a local entry point for OSG-bound jobs, adding a path to OSG may result in less waiting for your users.

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 the OSG 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 a access point (i.e., submit node, submit host) to submit their jobs to HTCondor, where the jobs wait ("are queued") until computing resources are 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 an OSG-managed pool. 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 resources are unavailable, have their jobs automatically flock to OSG. If you do not have an HTCondor batch system, following these instructions will install the HTCondor submit service and configure it only to forward jobs to the OSG. In other words, you do not need a whole HTCondor batch system just to have a local OSG access point.

System Requirements

The hardware requirement for an OSG access point 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 OSG, either as a computational resource 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 resource 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 be part of OSG, your access point should be registered with the OSG. 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

Next is to retrive a token so that the new submit host can authenticate with the Open Science Pool manager. Please use your COManage registered and approved identity to log into the OSG Token Registration. Once logged in, select Token on Docker, and find your registered submit node in the list. Follow the instructions (you probably have to do the steps on a host with Docker and as root), and once you have the token generated, keep that for later steps.

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. Note that you have to use OSG 3.6. Earlier versions will not work.

Once the YUM repositories are setup, install the osg-flock convenience RPM that installs all required packages. Example on a RHEL 7 host:

# yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
# yum install https://repo.opensciencegrid.org/osg/3.6/osg-3.6-el7-release-latest.rpm
# yum install osg-flock

Upgrading

Upgrading from previous versions should be as simple as switching to OSG 3.6, and then issuing yum upgrade. If you made local config changes, please verify that the files under /etc/condor/config.d were renamed/disabled during the upgrade.

Note that in some older versions of the package, the Gratia config was kept in /etc/gratia/condor/ProbeConfig. The new location is /etc/gratia/condor-ap/ProbeConfig.

The Open Science Pool will no longer accept GSI authentcation. Access points still configured with GSI, will have to be upgraded to OSG 3.6 and switched over to token authentication as described in this document.

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

Create a file named /etc/condor/tokens.d/ospool.token with the IDTOKEN you received earlier. 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 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 OSG

If your users are accustomed to running jobs locally, they may encounter some significant differences when running jobs in OSG. Users should be aware that OSG 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

OSG 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 double quotes are necessary. If not quoted, My_Project will be interpreted as an expression, and most likely evaluate to undefined, and prevent your job from running.

Get Help

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

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