Now that we have the temdir context manager I was thinking something like:
diff --git a/nova/utils.py b/nova/utils.py
index e375f11..a3ac896 100644
--- a/nova/utils.py
+++ b/nova/utils.py
@@ -61,9 +61,11 @@ ISO_TIME_FORMAT = "%Y-%m-%dT%H:%M:%S"
PERFECT_TIME_FORMAT = "%Y-%m-%dT%H:%M:%S.%f"
FLAGS = flags.FLAGS
-FLAGS.register_opt(
+FLAGS.register_opts([
cfg.BoolOpt('disable_process_locking', default=False,
- help='Whether to disable inter-process locks'))
+ help='Whether to disable inter-process locks'),
+ cfg.StrOpt('tempdir_location', default=None,
+ help='Path where tempdirs will be created')])
def import_class(import_str):
@@ -1611,6 +1613,7 @@ def temporary_chown(path, owner_uid=None):
@contextlib.contextmanager
def tempdir(**kwargs):
+ kwargs['dir'] = kwargs.get('dir', FLAGS.tempdir_location)
tmpdir = tempfile.mkdtemp(**kwargs)
try:
yield tmpdir
And get rid of the other flags that are used.
Vish
On Mar 16, 2012, at 5:51 PM, Pádraig Brady wrote:
> On 03/16/2012 11:57 PM, Justin Shepherd wrote:
>>
>>
>> On Mar 16, 2012, at 12:26, "Pádraig Brady" <p...@draigbrady.com> wrote:
>>
>>> On 03/16/2012 04:11 PM, Jay Pipes wrote:
>>>> Hi Stackers,
>>>>
>>>> So, in diagnosing a few things on TryStack yesterday, I ran into an
>>>> interesting problem with snapshotting that I'm hoping to get some advice
>>>> on.
>>>>
>>>> == The Problem ==
>>>>
>>>
>>>> QEMU was unhelpfully returning a vague error message of "error while
>>>> writing".
>>>
>>> That could be improved.
>>> As an aside, since qemu-img is mainly dealing with large files,
>>> it would be a prime candidate to call fallocate() from
>>> to get good layout for the files and immediate feedback
>>> if there isn't enough space.
>>>
>>> On a related note, I've a patch pending for after RC1
>>> that should auto clean any of these partially written files:
>>> https://review.openstack.org/#change,5442
>>>
>>>> As it turns out, the base operating system we install on our compute nodes
>>>> in TryStack has a (very) small root partition
>>>
>>>> == Possible Solutions ==
>>>>
>>>> So, there are a number of solutions that we can work on here, and I'm
>>>> wondering what the preference would be. Here are the solutions I have come
>>>> up with, along with a no-brainer improvement to Nova that would help in
>>>> diagnosing this problem:
>>>>
>>>> The no-brainer: Detect before attempting a snapshot that there is enough
>>>> space on a device to perform the operation, and if not, throw a useful
>>>> error message up the stack
>>>
>>> The space can change while writing, so you could still get the same error
>>> above.
>>>
>>>>
>>>> Solutions to the disk space problem:
>>>>
>>>> (1) Silly Jay, change the damn size of the root partition in your PXE base
>>>> OS install!
>>>>
>>>> Now, I'm no expert in creating customized base disk images, but from
>>>> looking at the build_pxe_env.sh script in devstack [1], it seems pretty
>>>> trivial to change the ramdisk_size parameter in the startup options to
>>>> something larger than 2109600. We could do this and reimage the compute
>>>> nodes one by one.
>>>>
>>>> (2) Make the location in which the snapshot is made configurable.
>>>>
>>>> Right now, as mentioned above, tempfile.mkdtemp() is used, which creates a
>>>> directory in the user's TMPDIR (typically /tmp, which is usually on the
>>>> root partition).
>>>>
>>>> We could add an option (--libvirt-snapshot-dir?) that would allow
>>>> nova-compute to override where that snapshot is built.
>>>>
>>>> (3) Change the user (running nova-compute) TMPDIR setting to something
>>>> different than /tmp on the root partition).
>>>
>>> I'd lean towards (3).
>>> That's something that depends on the environment (as you've nicely
>>> demonstrated),
>>> and also for security reasons the admin should be able to set TMPDIR.
>>> That's the standard way to do it, and it works already (hopefully).
>>
>> Actually I would argue that the best way to accomplish this would be option
>> #2. That way an admin/operator has control over the location. Not
>> manipulating this by messing around with a users environment variable.
>
> Well one can set the TMPDIR in the init script for the service.
> That's a fairly standard mechanism.
>
> (2) is good though if you would ever want to separate
> --libvirt-snapshot-dir from, $TMPDIR
>
> Now I can definitely see the need for changing TMPDIR from /tmp
> for Jay's reasons and /tmp being tmpfs by default on debian for example:
> http://lists.debian.org/debian-devel/2011/11/msg00281.html
> I'm not sure if you'd need to separate them?
> Though I'm always biased towards avoiding new config variables.
> I suppose one could argue you might want /tmp for small fast accesses,
> and something large and separate for manipulating large files.
>
> Now that I look at the existing nova uses of tmp dirs
> to store/stage large images, I see existing config vars:
>
> FLAGS.xenapi_sr_base_path # xens default Storage Repo
> FLAGS.image_decryption_dir # nova/image/s3.py
>
> So if you were following that you would implement (2) with:
>
> FLAGS.libvirt_snapshot_dir
>
> There might be opportunity to merge all three to:
>
> FLAGS.nova_image_staging_dir
>
> cheers,
> Pádraig.
>
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