[libvirt] [PATCH 2/2] qemu: Add pre-migration hook
Jiri Denemark
jdenemar at redhat.com
Tue Feb 28 21:49:10 UTC 2012
This hook is called during the Prepare phase on destination host and may
be used for changing domain XML.
---
docs/hooks.html.in | 35 +++++++++++++++++++++++------------
src/qemu/qemu_migration.c | 40 ++++++++++++++++++++++++++++++++++++++++
src/util/hooks.c | 3 ++-
src/util/hooks.h | 1 +
4 files changed, 66 insertions(+), 13 deletions(-)
diff --git a/docs/hooks.html.in b/docs/hooks.html.in
index 890359e..6c82c6d 100644
--- a/docs/hooks.html.in
+++ b/docs/hooks.html.in
@@ -120,6 +120,16 @@
called again, <span class="since">since 0.9.0</span>, to allow
any additional resource cleanup:<br/>
<pre>/etc/libvirt/hooks/qemu guest_name release end -</pre></li>
+ <li><span class="since">Since 0.9.11</span>, the qemu hook script
+ is also called at the beginning of incoming migration. It is called
+ as: <pre>/etc/libvirt/hooks/qemu 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 to, e.g., change
+ location of disk images for incoming domains.</li>
</ul>
<h5><a name="lxc">/etc/libvirt/hooks/lxc</a></h5>
@@ -161,19 +171,20 @@
source and destination hosts:</p>
<ol>
<li>At the beginning of the migration, the <i>qemu</i> hook script on
- the <b>destination</b> host is executed with the "start"
- operation.<br/><br/></li>
- <li>If this hook script returns indicating success (error code 0), the
- migration continues. Any other return code indicates failure, and
- the migration is aborted.<br/><br/></li>
- <li>The QEMU guest is then migrated to the destination host.<br/>
- <br/></li>
+ the <b>destination</b> host is executed with the "migrate"
+ operation.</li>
+ <li>Before QEMU process is spawned, the two operations ("prepare" and
+ "start") called for domain start are executed on
+ <b>destination</b> host.</li>
+ <li>If any of these hook script executions returns indicating success
+ (error code 0), the migration continues. Any other return code
+ indicates failure, and the migration is aborted.</li>
+ <li>The QEMU guest is then migrated to the destination host.</li>
<li>Unless an error occurs during the migration process, the <i>qemu</i>
- hook script on the <b>source</b> host is then executed with the "stopped"
- operation, to indicate it is no longer running on this
- host.<br/><br/>
- Regardless of the return code from this hook script, the migration
- is not aborted as it has already been performed.</li>
+ hook script on the <b>source</b> host is then executed with the
+ "stopped" and "release" operations to indicate it is no longer
+ running on this host. Regardless of the return codes, the
+ migration is not aborted as it has already been performed.</li>
</ol>
<br/>
diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
index 7df2d4f..d00bd61 100644
--- a/src/qemu/qemu_migration.c
+++ b/src/qemu/qemu_migration.c
@@ -47,6 +47,7 @@
#include "rpc/virnetsocket.h"
#include "storage_file.h"
#include "viruri.h"
+#include "hooks.h"
#define VIR_FROM_THIS VIR_FROM_QEMU
@@ -1130,6 +1131,7 @@ qemuMigrationPrepareAny(struct qemud_driver *driver,
qemuMigrationCookiePtr mig = NULL;
bool tunnel = !!st;
char *origname = NULL;
+ char *xmlout = NULL;
if (virTimeMillisNow(&now) < 0)
return -1;
@@ -1150,6 +1152,43 @@ qemuMigrationPrepareAny(struct qemud_driver *driver,
goto cleanup;
}
+ /* Let migration hook filter domain XML */
+ if (virHookPresent(VIR_HOOK_DRIVER_QEMU)) {
+ char *xml = virDomainDefFormat(def, VIR_DOMAIN_XML_SECURE);
+ int hookret;
+
+ hookret = virHookCall(VIR_HOOK_DRIVER_QEMU, def->name,
+ VIR_HOOK_QEMU_OP_MIGRATE, VIR_HOOK_SUBOP_BEGIN,
+ NULL, xml, &xmlout);
+ VIR_FREE(xml);
+
+ if (hookret < 0) {
+ goto cleanup;
+ } else if (hookret == 0) {
+ if (!*xmlout) {
+ VIR_DEBUG("Migrate hook filter returned nothing; using the"
+ " original XML");
+ } else {
+ virDomainDefPtr newdef;
+
+ VIR_DEBUG("Using hook-filtered domain XML: %s", xmlout);
+ newdef = virDomainDefParseString(driver->caps, xmlout,
+ QEMU_EXPECTED_VIRT_TYPES,
+ VIR_DOMAIN_XML_INACTIVE);
+ if (!newdef)
+ goto cleanup;
+
+ if (!virDomainDefCheckABIStability(def, newdef)) {
+ virDomainDefFree(newdef);
+ goto cleanup;
+ }
+
+ virDomainDefFree(def);
+ def = newdef;
+ }
+ }
+ }
+
if (virDomainObjIsDuplicate(&driver->domains, def, 1) < 0)
goto cleanup;
@@ -1244,6 +1283,7 @@ qemuMigrationPrepareAny(struct qemud_driver *driver,
cleanup:
VIR_FREE(origname);
+ VIR_FREE(xmlout);
virDomainDefFree(def);
VIR_FORCE_CLOSE(dataFD[0]);
VIR_FORCE_CLOSE(dataFD[1]);
diff --git a/src/util/hooks.c b/src/util/hooks.c
index 8c16a3a..b0c15fd 100644
--- a/src/util/hooks.c
+++ b/src/util/hooks.c
@@ -73,7 +73,8 @@ VIR_ENUM_IMPL(virHookQemuOp, VIR_HOOK_QEMU_OP_LAST,
"start",
"stopped",
"prepare",
- "release")
+ "release",
+ "migrate")
VIR_ENUM_IMPL(virHookLxcOp, VIR_HOOK_LXC_OP_LAST,
"start",
diff --git a/src/util/hooks.h b/src/util/hooks.h
index a53ac2c..7fd29f6 100644
--- a/src/util/hooks.h
+++ b/src/util/hooks.h
@@ -56,6 +56,7 @@ enum virHookQemuOpType {
VIR_HOOK_QEMU_OP_STOPPED, /* domain has stopped */
VIR_HOOK_QEMU_OP_PREPARE, /* domain startup initiated */
VIR_HOOK_QEMU_OP_RELEASE, /* domain destruction is over */
+ VIR_HOOK_QEMU_OP_MIGRATE, /* domain is being migrated */
VIR_HOOK_QEMU_OP_LAST,
};
--
1.7.8.5
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