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Job Router Configuration Overview

The HTCondor Job Router is at the heart of HTCondor-CE and allows admins to transform and direct jobs to specific batch systems. Customizations are made in the form of job routes where each route corresponds to a separate job transformation: If an incoming job matches a job route's requirements, the route creates a transformed job (referred to as the 'routed job') that is then submitted to the batch system. The CE package comes with default routes located in /etc/condor-ce/config.d/02-ce-*.conf that provide enough basic functionality for a small site.

If you have needs beyond delegating all incoming jobs to your batch system as they are, this document provides an overview of how to configure your HTCondor-CE Job Router

Definitions

  • Incoming Job: A job which was submitted to HTCondor-CE from an external source.
  • Routed Job: A job that has been transformed by the Job Router.

Route Syntaxes

HTCondor-CE 5 introduces the ability to write job routes using ClassAd transform syntax in addition to the existing configuration syntax. The old route configuration syntax continues to be the default in HTCondor-CE 5 but there are benefits to transitioning to the new syntax as outlined below.

ClassAd transforms

The HTCondor ClassAd transforms were originally introduced to HTCondor to perform in-place transformations of user jobs submitted to an HTCondor pool. In the HTCondor 8.9 series, the Job Router was updated to support transforms and HTCondor-CE 5 adds the configuration necessary to support routes written as ClassAd transforms. If configured to use trasnform-based routes, HTCondor-CE routes and transforms jobs that by chaining ClassAd transforms in the following order:

  1. Each transform in JOB_ROUTER_PRE_ROUTE_TRANSFORM_NAMES whose requirements are met by the job
  2. The first transform from JOB_ROUTER_ROUTE_NAMES whose requirements are met by the job. See the section on route matching below.
  3. Each transform in JOB_ROUTER_PRE_ROUTE_TRANSFORM_NAMES whose requirements are met by the job

New Job Router Transform Syntax

In HTCondor-CE 5.1.0 and 5.1.1, sites using the new Job Router transform syntax may run into issues with CPU and memory requests. This issue can be worked around by adding some extra lines to your job routes as described in the Maximum memory and Number of cores to request examples.

Deprecated syntax

Since the inception of HTCondor-CE, job routes have been written as a list of ClassAds. Each job route’s ClassAd is constructed by combining each entry from the JOB_ROUTER_ENTRIES with the JOB_ROUTER_DEFAULTS:

  • JOB_ROUTER_ENTRIES is a configuration variable whose default is set in /etc/condor-ce/config.d/02-ce-*.conf but may be overriden by the administrator in subsequent files in /etc/condor-ce/config.d/.
  • JOB_ROUTER_DEFAULTS is a generated configuration variable that sets default job route values that are required for HTCondor-CE's functionality. To view its contents in a readable format, run the following command:
    user@host $ condor_ce_config_val JOB_ROUTER_DEFAULTS | sed 's/;/;\n/g'
    

Take care when modifying attributes in JOB_ROUTER_DEFAULTS: you may add new attributes and override attributes that are set_* in JOB_ROUTER_DEFAULTS.

The following may break your HTCondor-CE

  • Do not set the JOB_ROUTER_DEFAULTS configuration variable yourself. This will cause the CE to stop functioning.
  • If a value is set in JOB_ROUTER_DEFAULTS with eval_set_<variable>, override it by using eval_set_<variable> in the JOB_ROUTER_ENTRIES. Do this at your own risk as it may cause the CE to break.

Choosing a syntax

For existing HTCondor-CEs, it's recommended that administrators continue to use the deprecated syntax (the default) and transition to ClassAd transforms at their own pace.

For new HTCondor-CEs, it's recommended that administrators start with ClassAd transforms. The ClassAd transform syntax provides many benefits including:

  • Statements being evaluated in the order they are written
  • Use of variables that are not included in the resultant job ad
  • Use of simple case statements

Additionally, it is now easier to include job transformations that should be evaluated before or after your routes by including transforms in the lists of JOB_ROUTER_PRE_ROUTE_TRANSFORM_NAMES and JOB_ROUTER_PRE_ROUTE_TRANSFORM_NAMES, respectively.

New Job Router Transform Syntax

In HTCondor-CE 5.1.0 and 5.1.1, sites using the new Job Router transform syntax may run into issues with CPU and memory requests. This issue can be worked around by adding some extra lines to your job routes as described in the Maximum memory and Number of cores to request examples.

How Jobs Match to Routes

The Job Router considers incoming jobs in the HTCondor-CE SchedD (i.e., jobs visible in condor_ce_q) that meet the following constraints:

  • The job has not already been considered by the Job Router
  • The job's universe is standard or vanilla

If the incoming job meets the above constraints, then the job is matched to the first route in JOB_ROUTER_ROUTE_NAMES whose requirements are satisfied by the job's ClassAd. Additionally:

  • If you are using the ClassAd transform syntax, transforms in JOB_ROUTER_PRE_ROUTE_TRANSFORM_NAMES and JOB_ROUTER_PRE_ROUTE_TRANSFORM_NAMES may also have their own requirements that determine whether or not that transform is applied.
  • If you are using the deprecated syntax, you may configure the Job Router to evenly distribute jobs across all matching routes (i.e., round-robin matching). To do so, add the following configuration to a file in /etc/condor-ce/config.d/:
    JOB_ROUTER_ROUND_ROBIN_SELECTION = True
    

Getting Help

If you have any questions or issues with configuring job routes, please contact us for assistance.