Re: [PATCH v2 2/4] iotests: Make qemu_nbd_popen() a contextmanager

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

28.07.2020 00:58, Nir Soffer wrote:
> Instead of duplicating the code to wait until the server is ready and
> remember to terminate the server and wait for it, make it possible to
> use like this:
> 
>      with qemu_nbd_popen('-k', sock, image):
>          # Access image via qemu-nbd socket...
> 
> Only test 264 used this helper, but I had to modify the output since it
> did not consistently when starting and stopping qemu-nbd.
> 
> Signed-off-by: Nir Soffer <nsoffer@redhat.com>
> ---
>   tests/qemu-iotests/264        | 76 +++++++++++++----------------------
>   tests/qemu-iotests/264.out    |  2 +
>   tests/qemu-iotests/iotests.py | 28 ++++++++++++-
>   3 files changed, 56 insertions(+), 50 deletions(-)
> 
> diff --git a/tests/qemu-iotests/264 b/tests/qemu-iotests/264
> index 304a7443d7..666f164ed8 100755
> --- a/tests/qemu-iotests/264
> +++ b/tests/qemu-iotests/264
> @@ -36,48 +36,32 @@ wait_step = 0.2
>   
>   qemu_img_create('-f', iotests.imgfmt, disk_a, str(size))
>   qemu_img_create('-f', iotests.imgfmt, disk_b, str(size))
> -srv = qemu_nbd_popen('-k', nbd_sock, '-f', iotests.imgfmt, disk_b)
>   
> -# Wait for NBD server availability
> -t = 0
> -ok = False
> -while t < wait_limit:
> -    ok = qemu_io_silent_check('-f', 'raw', '-c', 'read 0 512', nbd_uri)
> -    if ok:
> -        break
> -    time.sleep(wait_step)
> -    t += wait_step
> +with qemu_nbd_popen('-k', nbd_sock, '-f', iotests.imgfmt, disk_b):
> +    vm = iotests.VM().add_drive(disk_a)
> +    vm.launch()
> +    vm.hmp_qemu_io('drive0', 'write 0 {}'.format(size))
> +
> +    vm.qmp_log('blockdev-add', filters=[iotests.filter_qmp_testfiles],
> +               **{'node_name': 'backup0',
> +                  'driver': 'raw',
> +                  'file': {'driver': 'nbd',
> +                           'server': {'type': 'unix', 'path': nbd_sock},
> +                           'reconnect-delay': 10}})
> +    vm.qmp_log('blockdev-backup', device='drive0', sync='full', target='backup0',
> +               speed=(1 * 1024 * 1024))
> +
> +    # Wait for some progress
> +    t = 0
> +    while t < wait_limit:
> +        jobs = vm.qmp('query-block-jobs')['return']
> +        if jobs and jobs[0]['offset'] > 0:
> +            break
> +        time.sleep(wait_step)
> +        t += wait_step
>   
> -assert ok
> -
> -vm = iotests.VM().add_drive(disk_a)
> -vm.launch()
> -vm.hmp_qemu_io('drive0', 'write 0 {}'.format(size))
> -
> -vm.qmp_log('blockdev-add', filters=[iotests.filter_qmp_testfiles],
> -           **{'node_name': 'backup0',
> -              'driver': 'raw',
> -              'file': {'driver': 'nbd',
> -                       'server': {'type': 'unix', 'path': nbd_sock},
> -                       'reconnect-delay': 10}})
> -vm.qmp_log('blockdev-backup', device='drive0', sync='full', target='backup0',
> -           speed=(1 * 1024 * 1024))
> -
> -# Wait for some progress
> -t = 0
> -while t < wait_limit:
> -    jobs = vm.qmp('query-block-jobs')['return']
>       if jobs and jobs[0]['offset'] > 0:
> -        break
> -    time.sleep(wait_step)
> -    t += wait_step
> -
> -if jobs and jobs[0]['offset'] > 0:
> -    log('Backup job is started')
> -
> -log('Kill NBD server')
> -srv.kill()
> -srv.wait()
> +        log('Backup job is started')
>   
>   jobs = vm.qmp('query-block-jobs')['return']
>   if jobs and jobs[0]['offset'] < jobs[0]['len']:
> @@ -88,12 +72,8 @@ vm.qmp_log('block-job-set-speed', device='drive0', speed=0)
>   # Emulate server down time for 1 second
>   time.sleep(1)
>   
> -log('Start NBD server')
> -srv = qemu_nbd_popen('-k', nbd_sock, '-f', iotests.imgfmt, disk_b)
> -
> -e = vm.event_wait('BLOCK_JOB_COMPLETED')
> -log('Backup completed: {}'.format(e['data']['offset']))
> -
> -vm.qmp_log('blockdev-del', node_name='backup0')
> -srv.kill()
> -vm.shutdown()
> +with qemu_nbd_popen('-k', nbd_sock, '-f', iotests.imgfmt, disk_b):
> +    e = vm.event_wait('BLOCK_JOB_COMPLETED')
> +    log('Backup completed: {}'.format(e['data']['offset']))
> +    vm.qmp_log('blockdev-del', node_name='backup0')
> +    vm.shutdown()
> diff --git a/tests/qemu-iotests/264.out b/tests/qemu-iotests/264.out
> index 3000944b09..c45b1e81ef 100644
> --- a/tests/qemu-iotests/264.out
> +++ b/tests/qemu-iotests/264.out
> @@ -1,3 +1,4 @@
> +Start NBD server
>   {"execute": "blockdev-add", "arguments": {"driver": "raw", "file": {"driver": "nbd", "reconnect-delay": 10, "server": {"path": "TEST_DIR/PID-nbd-sock", "type": "unix"}}, "node-name": "backup0"}}
>   {"return": {}}
>   {"execute": "blockdev-backup", "arguments": {"device": "drive0", "speed": 1048576, "sync": "full", "target": "backup0"}}
> @@ -11,3 +12,4 @@ Start NBD server
>   Backup completed: 5242880
>   {"execute": "blockdev-del", "arguments": {"node-name": "backup0"}}
>   {"return": {}}
> +Kill NBD server
> diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
> index 3590ed78a0..8f79668435 100644
> --- a/tests/qemu-iotests/iotests.py
> +++ b/tests/qemu-iotests/iotests.py
> @@ -28,10 +28,13 @@ import signal
>   import struct
>   import subprocess
>   import sys
> +import time
>   from typing import (Any, Callable, Dict, Iterable,
>                       List, Optional, Sequence, Tuple, TypeVar)
>   import unittest
>   
> +from contextlib import contextmanager
> +
>   # pylint: disable=import-error, wrong-import-position
>   sys.path.append(os.path.join(os.path.dirname(__file__), '..', '..', 'python'))
>   from qemu import qtest
> @@ -270,9 +273,30 @@ def qemu_nbd_early_pipe(*args):
>   
>       return subp.returncode, output if subp.returncode else ''
>   
> +@contextmanager
>   def qemu_nbd_popen(*args):
> -    '''Run qemu-nbd in daemon mode and return the parent's exit code'''
> -    return subprocess.Popen(qemu_nbd_args + ['--persistent'] + list(args))
> +    '''Context manager running qemu-nbd within the context'''

PEP8 (or some another PEP referenced in PEP8) asks to use """ for doc-strings

> +    pid_file = file_path("pid")
> +
> +    cmd = list(qemu_nbd_args)
> +    cmd.extend(('--persistent', '--pid-file', pid_file))
> +    cmd.extend(args)
> +
> +    log('Start NBD server')
> +    p = subprocess.Popen(cmd)
> +    try:
> +        while not os.path.exists(pid_file):
> +            if p.poll() is not None:
> +                raise RuntimeError(
> +                    "qemu-nbd terminated with exit code {}: {}"
> +                    .format(p.returncode, ' '.join(cmd)))
> +
> +            time.sleep(0.01)
> +        yield
> +    finally:
> +        log('Kill NBD server')
> +        p.kill()
> +        p.wait()

why do we need try-finally? I think, the only possible exception is your "raise RuntimeError", and in this case the process is alredy dead, no need to kill it (and print the log message)

>   
>   def compare_images(img1, img2, fmt1=imgfmt, fmt2=imgfmt):
>       '''Return True if two image files are identical'''
> 

anyway:
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

-- 
Best regards,
Vladimir