doc/html/preemption_plugins.shtml

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<h1><a name="top">SLURM Preemption Plugin API</a></h1>

<h2> Overview</h2>
<p> This document describes SLURM preemption plugins and the API that defines
them. It is intended as a resource to programmers wishing to write their own
SLURM preemption plugins. This is version 100 of the API.</p>

<p>SLURM preemption plugins are SLURM plugins that identify which jobs
can be preempted by a pending job. They must conform to the SLURM Plugin
API with the following specifications:</p>

<p><span class="commandline">const char
plugin_type[]="<i>major/minor</i>"</span><br>
The major type must be &quot;preempt.&quot; The minor type can be any
recognizable abbreviation for the type of preemption.
We recommend, for example:</p>

<ul>
<li><b>none</b>&#151;This plugin prevents any job preemption.</li>
<li><b>partition_prio</b>&#151;This plugin permit pending jobs from one
partition to preempt jobs from a lower priority partition.</li>
<li><b>qos</b>&#151;This plugin permits jobs to preempt others based
upon their Quality Of Service values as defined in the SLURM database.</li>
</ul>

<p>The <span class="commandline">plugin_name</span> and
<span class="commandline">plugin_version</span> symbols required by the SLURM
Plugin API require no specialization for job preemption support.
Note carefully, however, the versioning discussion below.</p>

<p>The programmer is urged to study
<span class="commandline">src/plugins/preempt/partition_prio/preempt_partition_prio.c</span>
for an example implementation of a SLURM preemption plugin.</p>

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<h2>API Functions</h2>
<p>The following functions must appear. Functions which are not implemented
should be stubbed.</p>

<p class="commandline">List find_preemptable_jobs(
struct job_record *job_ptr)</p>
<p style="margin-left:.2in"><b>Description</b>: Identifies the jobs
which can be preempted by a specific pending job.</p>
<p style="margin-left:.2in"><b>Arguments</b>:<br>
<span class="commandline">job_ptr</span> (input) a pointer to the
pending job which is attempting to be started</p>
<p style="margin-left:.2in"><b>Returns</b>: A list of pointers to
jobs which may be preempted.
The list should be be released using the <i>list_destroy</i> function when
no longer required.
This list should be sorted in order from most attractive to
preempt to least attractive to preempt (e.g. lowest to highest priority).
For example, even within a given partition or QOS one might want to
smaller jobs first.</p>

<h2>Versioning</h2>
<p> This document describes version 100 of the SLURM Preemption API. Future
releases of SLURM may revise this API. A preemption plugin conveys its ability
to implement a particular API version using the mechanism outlined for SLURM
plugins.</p>

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<p style="text-align:center;">Last modified 5 October 2009</p>

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