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libxl: add hooks support

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Introduce libxl hook and use it for start, prepare, started,
stop, stopped, migrate events.
This commit is contained in:
Cédric Bosdonnat
2016-07-11 13:55:53 +02:00
parent a9aafc0aa0
commit 7d3b2eb58f
6 changed files with 232 additions and 3 deletions
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53
docs/hooks.html.in
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@@ -17,8 +17,10 @@
(<span class="since">since 0.8.0</span>)<br/><br/></li>
<li>A QEMU guest is started or stopped
(<span class="since">since 0.8.0</span>)<br/><br/></li>
<li>An LXC guest is started or stopped
<li>An LXC guest is started or stopped
(<span class="since">since 0.8.0</span>)<br/><br/></li>
<li>A libxl-handled Xen guest is started or stopped
(<span class="since">since 2.1.0</span>)<br/><br/></li>
<li>A network is started or stopped or an interface is
plugged/unplugged to/from the network
(<span class="since">since 1.2.2</span>)<br/><br/></li>
@@ -41,7 +43,7 @@
<br/>
<h2><a name="names">Script names</a></h2>
<p>At present, there are three hook scripts that can be called:</p>
<p>At present, there are five hook scripts that can be called:</p>
<ul>
<li><code>/etc/libvirt/hooks/daemon</code><br/><br/>
Executed when the libvirt daemon is started, stopped, or reloads
@@ -50,6 +52,9 @@
Executed when a QEMU guest is started, stopped, or migrated<br/><br/></li>
<li><code>/etc/libvirt/hooks/lxc</code><br /><br/>
Executed when an LXC guest is started or stopped</li>
<li><code>/etc/libvirt/hooks/libxl</code><br/><br/>
Executed when a libxl-handled Xen guest is started, stopped, or
migrated<br/><br/></li>
<li><code>/etc/libvirt/hooks/network</code><br/><br/>
Executed when a network is started or stopped or an
interface is plugged/unplugged to/from the network</li>
@@ -235,6 +240,50 @@
</li>
</ul>
<h5><a name="libxl">/etc/libvirt/hooks/libxl</a></h5>
<ul>
<li>Before a Xen guest is started using libxl driver, the libxl hook
script is called in three locations; if any location fails, the guest
is not started. The first location, <span class="since">since
2.1.0</span>, is before libvirt performs any resource
labeling, and the hook can allocate resources not managed by
libvirt. This is called as:<br/>
<pre>/etc/libvirt/hooks/libxl guest_name prepare begin -</pre>
The second location, available <span class="since">Since
2.1.0</span>, occurs after libvirt has finished labeling
all resources, but has not yet started the guest, called as:<br/>
<pre>/etc/libvirt/hooks/libxl guest_name start begin -</pre>
The third location, <span class="since">2.1.0</span>,
occurs after the domain has successfully started up:<br/>
<pre>/etc/libvirt/hooks/libxl guest_name started begin -</pre>
</li>
<li>When a libxl-handled Xen guest is stopped, the libxl hook script
is called in two locations, to match the startup.
First, <span class="since">since 2.1.0</span>, the hook is
called before libvirt restores any labels:<br/>
<pre>/etc/libvirt/hooks/libxl guest_name stopped end -</pre>
Then, after libvirt has released all resources, the hook is
called again, <span class="since">since 2.1.0</span>, to allow
any additional resource cleanup:<br/>
<pre>/etc/libvirt/hooks/libxl guest_name release end -</pre></li>
<li><span class="since">Since 2.1.0</span>, the libxl hook script
is also called at the beginning of incoming migration. It is called
as: <pre>/etc/libvirt/hooks/libxl guest_name migrate begin -</pre>
with domain XML sent to standard input of the script. In this case,
the script acts as a filter and is supposed to modify the domain
XML and print it out on its standard output. Empty output is
identical to copying the input XML without changing it. In case the
script returns failure or the output XML is not valid, incoming
migration will be canceled. This hook may be used, e.g., to change
location of disk images for incoming domains.</li>
<li><span class="since">Since 2.1.0</span>, the libxl hook script
is also called when the libvirtd daemon restarts and reconnects
to previously running Xen domains. If the script fails, the
existing Xen domains will be killed off. It is called as:
<pre>/etc/libvirt/hooks/libxl guest_name reconnect begin -</pre>
</li>
</ul>
<h5><a name="network">/etc/libvirt/hooks/network</a></h5>
<ul>
<li><span class="since">Since 1.2.2</span>, before a network is started,