Change in vdsm[master]: qemuimg: Memoize _supports_qcow2_compat

[Nir Soffer]

Nir Soffer has uploaded a new change for review.

Change subject: qemuimg: Memoize _supports_qcow2_compat
......................................................................

qemuimg: Memoize _supports_qcow2_compat

We used to run qemu-img twice when creating or converting qcow2 images.
The first run check if qemu-img supports the qcow2 "comapt" option, and
the second run uses the result to format the qemu-img command.

Now we run qemu-img once for "create" and "convert" to learn about
its
capabilities, and use the cached value on the next runs. If qemu-img
executable is modified, we drop the cache, in case a new version was
installed with different capabilities.

Change-Id: Ic63f5e8c06993df8e4066bf7ac2dabfb4b4bdbfb
Signed-off-by: Nir Soffer <nsoffer(a)redhat.com&gt;
---
M lib/vdsm/qemuimg.py
M tests/qemuimgTests.py
2 files changed, 8 insertions(+), 0 deletions(-)


  git pull ssh://gerrit.ovirt.org:29418/vdsm refs/changes/11/34711/1

diff --git a/lib/vdsm/qemuimg.py b/lib/vdsm/qemuimg.py
index cf428b2..f295acc 100644
--- a/lib/vdsm/qemuimg.py
+++ b/lib/vdsm/qemuimg.py
@@ -23,6 +23,7 @@
 import signal
 
 from . import utils
+from . import cache
 
 _qemuimg = utils.CommandPath("qemu-img",
                              "/usr/bin/qemu-img",)  # Fedora, EL6
@@ -221,6 +222,7 @@
         raise QImgError(rc, out, err)
 
 
+(a)cache.memoized(cache.file_validator(_qemuimg.cmd))
 def _supports_qcow2_compat(command):
     """
     qemu-img "create" and "convert" commands support a
"compat" option in
diff --git a/tests/qemuimgTests.py b/tests/qemuimgTests.py
index 813a497..a642374 100644
--- a/tests/qemuimgTests.py
+++ b/tests/qemuimgTests.py
@@ -118,6 +118,9 @@
 
 class CreateTests(TestCaseBase):
 
+    def setUp(self):
+        qemuimg._supports_qcow2_compat.invalidate()
+
     def test_no_format(self):
         def create(cmd, **kw):
             expected = [QEMU_IMG, 'create', 'image']
@@ -161,6 +164,9 @@
 
 class ConvertTests(TestCaseBase):
 
+    def setUp(self):
+        qemuimg._supports_qcow2_compat.invalidate()
+
     def test_no_format(self):
         def convert(cmd, **kw):
             expected = [QEMU_IMG, 'convert', '-t', 'none',
'src', 'dst']


-- 
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Gerrit-MessageType: newchange
Gerrit-Change-Id: Ic63f5e8c06993df8e4066bf7ac2dabfb4b4bdbfb
Gerrit-PatchSet: 1
Gerrit-Project: vdsm
Gerrit-Branch: master
Gerrit-Owner: Nir Soffer <nsoffer(a)redhat.com&gt;