Re: [PATCH v3 2/4] iotests: Switch nbd tests to use Unix rather than TCP

[Max Reitz]

On 18.11.19 18:42, Eric Blake wrote:
> On 11/18/19 11:29 AM, Max Reitz wrote:
>> On 14.11.19 22:34, Eric Blake wrote:
>>> Up to now, all it took to cause a lot of iotest failures was to have a
>>> background process such as 'nbdkit -p 10810 null' running, because we
>>> hard-coded the TCP port.  Switching to a Unix socket eliminates this
>>> contention.  We still have TCP coverage in test 233, and that test is
>>> more careful to not pick a hard-coded port.
>>
>> For me, all it took was to run qcow2 and nbd tests in parallel (some
>> qcow2 tests create nbd servers, too), so this is great.
>>
>>> Signed-off-by: Eric Blake <address@hidden>
>>> ---
>>>   tests/qemu-iotests/common.filter | 6 ++++--
>>>   tests/qemu-iotests/common.rc     | 8 ++++----
>>>   2 files changed, 8 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/tests/qemu-iotests/common.filter
>>> b/tests/qemu-iotests/common.filter
>>> index f870e00e4421..5367deea398e 100644
>>> --- a/tests/qemu-iotests/common.filter
>>> +++ b/tests/qemu-iotests/common.filter
>>> @@ -127,7 +127,8 @@ _filter_img_create()
>>>           -e "s#$TEST_DIR#TEST_DIR#g" \
>>>           -e "s#$SOCK_DIR#SOCK_DIR#g" \
>>>           -e "s#$IMGFMT#IMGFMT#g" \
>>> -        -e 's#nbd:127.0.0.1:10810#TEST_DIR/t.IMGFMT#g' \
>>> +        -e 's#nbd:127.0.0.1:[0-9]\\+#TEST_DIR/t.IMGFMT#g' \
>>> +        -e 's#nbd+unix:///\??socket=SOCK_DIR/nbd#TEST_DIR/t.IMGFMT#g' \
>>
>> Why the second question mark?  I thought the ? after the /// was
>> mandatory.
> 
> Some of our code outputs:
> 
> nbd+unix://?socket=...
> 
> when there is no export name, while other outputs:
> 
> nbd+unix:///?socket=...
> 
> When there IS an export name, it outputs
> 
> nbd+unix:///name?socket=...
> 
> So the regex is matching 2 or 3 / (using \? to make the third optional),
> then a mandatory ?.

Ah, I mixed up the escaping, as I often do when dealing with regexes.

>>> +++ b/tests/qemu-iotests/common.rc
>>> @@ -217,7 +217,7 @@ if [ "$IMGOPTSSYNTAX" = "true" ]; then
>>>           TEST_IMG="$DRIVER,file.filename=$TEST_DIR/t.$IMGFMT"
>>>       elif [ "$IMGPROTO" = "nbd" ]; then
>>>           TEST_IMG_FILE=$TEST_DIR/t.$IMGFMT
>>> -       
>>> TEST_IMG="$DRIVER,file.driver=nbd,file.host=127.0.0.1,file.port=10810"
>>> +       
>>> TEST_IMG="$DRIVER,file.driver=nbd,file.type=unix,file.path=$SOCKDIR/$IMGFMT"
>>>
>>
>> Maybe nbd.$IMGFMT?
> 
> At first glance, it seems reasonable.  But reading further,
> 
>>
>>>       elif [ "$IMGPROTO" = "ssh" ]; then
>>>           TEST_IMG_FILE=$TEST_DIR/t.$IMGFMT
>>>          
>>> TEST_IMG="$DRIVER,file.driver=ssh,file.host=127.0.0.1,file.path=$TEST_IMG_FILE"
>>>
>>> @@ -233,7 +233,7 @@ else
>>>           TEST_IMG=$TEST_DIR/t.$IMGFMT
>>>       elif [ "$IMGPROTO" = "nbd" ]; then
>>>           TEST_IMG_FILE=$TEST_DIR/t.$IMGFMT
>>> -        TEST_IMG="nbd:127.0.0.1:10810"
>>> +        TEST_IMG="nbd+unix:///?socket=$SOCK_DIR/nbd"
>>
>> Shouldn’t this be $IMGFMT, too (instead of nbd)?  (Or maybe nbd.$IMGFMT)
> 
> Now I'm starting to wonder.  With NBD and non-raw, there are two places
> to do the image format:
> 
> qcow2 file -> qemu-nbd -f qcow2 -> raw bytes over NBD -> qemu client -f
> raw -> guest  (our typical usage)
> 
> qcow2 file -> qemu-nbd -f raw -> qcow2 bytes over NBD -> qemu client -f
> qcow2 -> guest  (limited use, since NBD does not [yet] have resize support]
> 
> so naming the socket $SOCK_DIR/nbd.qcow2 when the socket carries raw
> data (our typical use) seems awkward.  But then again, running './check
> -qcow2 -nbd' shows that we seldom test qcow2 format over nbd protocol
> (precisely because nbd does not yet have resize).

Yes, the socket would carry qcow2 data.  Which doesn’t work (and I don’t
see a reason why we’d want it), but, well.

> If anything, I'm inclined to use $SOCK_DIR/nbd.raw to indicate that the
> NBD client sees raw format, regardless of the format in use by the
> server, to leave the door open for $SOCK_DIR/nbd.qcow2 when we finally
> are happy to test qcow2 format over NBD.

Sure, works for me.

> Or stick to just $SOCK_DIR/nbd hard-coded everywhere, and quit trying to
> use $IMGFMT in the socket name, to make all the usage consistent.

Works for me, too.

Max

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