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  <div class="section" id="ganeti-bulk-create">
<h1><a class="toc-backref" href="#id1">Ganeti Bulk Create</a><a class="headerlink" href="#ganeti-bulk-create" title="Permalink to this headline"></a></h1>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Created:</th><td class="field-body">2012-Sep-03</td>
</tr>
<tr class="field-even field"><th class="field-name">Status:</th><td class="field-body">Implemented</td>
</tr>
<tr class="field-odd field"><th class="field-name">Ganeti-Version:</th><td class="field-body">2.7.0</td>
</tr>
</tbody>
</table>
<div class="contents topic" id="contents">
<p class="topic-title first">Contents</p>
<ul class="simple">
<li><a class="reference internal" href="#ganeti-bulk-create" id="id1">Ganeti Bulk Create</a><ul>
<li><a class="reference internal" href="#current-state-and-shortcomings" id="id2">Current state and shortcomings</a><ul>
<li><a class="reference internal" href="#proposed-changes" id="id3">Proposed changes</a></li>
<li><a class="reference internal" href="#problems" id="id4">Problems</a></li>
</ul>
</li>
<li><a class="reference internal" href="#implementation" id="id5">Implementation</a><ul>
<li><a class="reference internal" href="#iallocator" id="id6">IAllocator</a></li>
<li><a class="reference internal" href="#opinstancebulkadd" id="id7">OpInstanceBulkAdd</a></li>
</ul>
</li>
</ul>
</li>
</ul>
</div>
<div class="section" id="current-state-and-shortcomings">
<h2><a class="toc-backref" href="#id2">Current state and shortcomings</a><a class="headerlink" href="#current-state-and-shortcomings" title="Permalink to this headline"></a></h2>
<p>Creation of instances happens a lot. A fair load is done by just
creating instances and due to bad allocation shifting them around later
again. Additionally, if you turn up a new cluster you already know a
bunch of instances, which need to exists on the cluster. Doing this
one-by-one is not only cumbersome but might also fail, due to lack of
resources or lead to badly balanced clusters.</p>
<p>Since the early Ganeti 2.0 alpha version there is a <code class="docutils literal"><span class="pre">gnt-instance</span>
<span class="pre">batch-create</span></code> command to allocate a bunch of instances based on a json
file. This feature, however, doesn’t take any advantages of iallocator
and submits jobs in a serialized manner.</p>
<div class="section" id="proposed-changes">
<h3><a class="toc-backref" href="#id3">Proposed changes</a><a class="headerlink" href="#proposed-changes" title="Permalink to this headline"></a></h3>
<p>To overcome this shortcoming we would extend the current iallocator
interface to allow bulk requests. On the Ganeti side, a new opcode is
introduced to handle the bulk creation and returning the resulting
placement from the <a class="reference internal" href="#iallocator">IAllocator</a>.</p>
</div>
<div class="section" id="problems">
<h3><a class="toc-backref" href="#id4">Problems</a><a class="headerlink" href="#problems" title="Permalink to this headline"></a></h3>
<p>Due to the design of chained jobs, we can guarantee, that with the state
at which the <code class="docutils literal"><span class="pre">multi-alloc</span></code> opcode is run, all of the instances will
fit (or all won’t). But we can’t guarantee that once the instance
creation requests were submit, no other jobs have sneaked in between.
This might still lead to failing jobs because the resources have changed
in the meantime.</p>
</div>
</div>
<div class="section" id="implementation">
<h2><a class="toc-backref" href="#id5">Implementation</a><a class="headerlink" href="#implementation" title="Permalink to this headline"></a></h2>
<div class="section" id="iallocator">
<h3><a class="toc-backref" href="#id6">IAllocator</a><a class="headerlink" href="#iallocator" title="Permalink to this headline"></a></h3>
<p>A new additional <code class="docutils literal"><span class="pre">type</span></code> will be added called <code class="docutils literal"><span class="pre">multi-allocate</span></code> to
distinguish between normal and bulk operation. For the bulk operation
the <code class="docutils literal"><span class="pre">request</span></code> will be a finite list of request dicts.</p>
<p>If <code class="docutils literal"><span class="pre">multi-allocate</span></code> is declared, <code class="docutils literal"><span class="pre">request</span></code> must exist and is a list
of <code class="docutils literal"><span class="pre">request</span></code> dicts as described in <a class="reference internal" href="iallocator.html"><span class="doc">Operation specific input</span></a>. The <code class="docutils literal"><span class="pre">result</span></code> then is a list of instance name and node
placements in the order of the <code class="docutils literal"><span class="pre">request</span></code> field.</p>
<p>In addition, the old <code class="docutils literal"><span class="pre">allocate</span></code> request type will be deprecated and at
latest in Ganeti 2.8 incorporated into this new request. Current code
will need slight adaption to work with the new request. This needs
careful testing.</p>
</div>
<div class="section" id="opinstancebulkadd">
<h3><a class="toc-backref" href="#id7">OpInstanceBulkAdd</a><a class="headerlink" href="#opinstancebulkadd" title="Permalink to this headline"></a></h3>
<p>We add a new opcode <code class="docutils literal"><span class="pre">OpInstanceBulkAdd</span></code>. It receives a list of
<code class="docutils literal"><span class="pre">OpInstanceCreate</span></code> on the <code class="docutils literal"><span class="pre">instances</span></code> field. This is done to make
sure, that these two loosely coupled opcodes do not get out of sync. On
the RAPI side, however, this just is a list of instance create
definitions. And the client is adapted accordingly.</p>
<p>The opcode itself does some sanity checks on the instance creation
opcodes which includes:</p>
<ul class="simple">
<li><code class="docutils literal"><span class="pre">mode</span></code> is not set</li>
<li><code class="docutils literal"><span class="pre">pnode</span></code> and <code class="docutils literal"><span class="pre">snodes</span></code> is not set</li>
<li><code class="docutils literal"><span class="pre">iallocator</span></code> is not set</li>
</ul>
<p>Any of the above error will be aborted with <code class="docutils literal"><span class="pre">OpPrereqError</span></code>. Once the
list has been verified it is handed to the <code class="docutils literal"><span class="pre">iallocator</span></code> as described
in <a class="reference internal" href="#iallocator">IAllocator</a>. Upon success we then return the result of the
<a class="reference internal" href="#iallocator">IAllocator</a> call.</p>
<p>At this point the current instance allocation would work with the
resources available on the cluster as perceived upon
<code class="docutils literal"><span class="pre">OpInstanceBulkAdd</span></code> invocation. However, there might be corner cases
where this is not true as described in <a class="reference internal" href="#problems">Problems</a>.</p>
</div>
</div>
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  <h3><a href="index.html">Table Of Contents</a></h3>
  <ul>
<li><a class="reference internal" href="#">Ganeti Bulk Create</a><ul>
<li><a class="reference internal" href="#current-state-and-shortcomings">Current state and shortcomings</a><ul>
<li><a class="reference internal" href="#proposed-changes">Proposed changes</a></li>
<li><a class="reference internal" href="#problems">Problems</a></li>
</ul>
</li>
<li><a class="reference internal" href="#implementation">Implementation</a><ul>
<li><a class="reference internal" href="#iallocator">IAllocator</a></li>
<li><a class="reference internal" href="#opinstancebulkadd">OpInstanceBulkAdd</a></li>
</ul>
</li>
</ul>
</li>
</ul>

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