Re: [Qemu-devel] [Qemu-block] [PATCH 3/3] iotests: Allow 147 to be run concurrently

[Max Reitz]

On 21.01.19 21:50, John Snow wrote:
> 
> 
> On 12/21/18 6:47 PM, Max Reitz wrote:
>> To do this, we need to allow creating the NBD server on various ports
>> instead of a single one (which may not even work if you run just one
>> instance, because something entirely else might be using that port).
>>
>> So we just pick a random port in [32768, 32768 + 1024) and try to create
>> a server there.  If that fails, we just retry until something sticks.
>>
>> For the IPv6 test, we need a different range, though (just above that
>> one).  This is because "localhost" resolves to both 127.0.0.1 and ::1.
>> This means that if you bind to it, it will bind to both, if possible, or
>> just one if the other is already in use.  Therefore, if the IPv6 test
>> has already taken [::1]:some_port and we then try to take
>> localhost:some_port, that will work -- only the second server will be
>> bound to 127.0.0.1:some_port alone and not [::1]:some_port in addition.
>> So we have two different servers on the same port, one for IPv4 and one
>> for IPv6.
>>
>> But when we then try to connect to the server through
>> localhost:some_port, we will always end up at the IPv6 one (as long as
>> it is up), and this may not be the one we want.
>>
>> Thus, we must make sure not to create an IPv6-only NBD server on the
>> same port as a normal "dual-stack" NBD server -- which is done by using
>> distinct port ranges, as explained above.
>>
>> Signed-off-by: Max Reitz <address@hidden>
>> ---
>>  tests/qemu-iotests/147 | 98 +++++++++++++++++++++++++++++-------------
>>  1 file changed, 68 insertions(+), 30 deletions(-)
>>
>> diff --git a/tests/qemu-iotests/147 b/tests/qemu-iotests/147
>> index 3e10a9969e..82513279b0 100755
>> --- a/tests/qemu-iotests/147
>> +++ b/tests/qemu-iotests/147
>> @@ -19,13 +19,17 @@
>>  #
>>  
>>  import os
>> +import random
>>  import socket
>>  import stat
>>  import time
>>  import iotests
>> -from iotests import cachemode, imgfmt, qemu_img, qemu_nbd
>> +from iotests import cachemode, imgfmt, qemu_img, qemu_nbd, qemu_nbd_pipe
>>  
>> -NBD_PORT = 10811
>> +NBD_PORT_START      = 32768
>> +NBD_PORT_END        = NBD_PORT_START + 1024
>> +NBD_IPV6_PORT_START = NBD_PORT_END
>> +NBD_IPV6_PORT_END   = NBD_IPV6_PORT_START + 1024
>>  
>>  test_img = os.path.join(iotests.test_dir, 'test.img')
>>  unix_socket = os.path.join(iotests.test_dir, 'nbd.socket')
>> @@ -88,17 +92,29 @@ class QemuNBD(NBDBlockdevAddBase):
>>          except OSError:
>>              pass
>>  
>> +    def _try_server_up(self, *args):
>> +        status, msg = qemu_nbd_pipe('-f', imgfmt, test_img, *args)
>> +        if status == 0:
>> +            return True
>> +        if 'Address already in use' in msg:
>> +            return False
> 
> My only half-empty question is if we are guaranteed to have a locale and
> environment such that this string will always be present when we
> encounter that specific error?
> 
> I suppose even if not, that it'll just fail hard and it's no worse than
> what we had before.

I can tell you at least that my locale is de_DE.UTF-8.

>> +        self.fail(msg)
>> +
>>      def _server_up(self, *args):
>> -        self.assertEqual(qemu_nbd('-f', imgfmt, test_img, *args), 0)
>> +        self.assertTrue(self._try_server_up(*args))
>>  
>>      def test_inet(self):
>> -        self._server_up('-b', 'localhost', '-p', str(NBD_PORT))
>> +        while True:
>> +            nbd_port = random.randrange(NBD_PORT_START, NBD_PORT_END)
>> +            if self._try_server_up('-b', 'localhost', '-p', str(nbd_port)):
>> +                break
> 
> Why not just iterate over the range so that once the range is exhausted
> we're guaranteed to fail?

Hm.  With this approach chances are higher that the first port you try
works, so it does have a benefit.  I'm not sure whether it's actually a
problem that this will pretty much break down if everything in the range
is allocated, because I can't see that happening.

Iterating over a range wouldn't make the code easier because I would
have to account for the error case. O:-)

>> +
>>          address = { 'type': 'inet',
>>                      'data': {
>>                          'host': 'localhost',
>> -                        'port': str(NBD_PORT)
>> +                        'port': str(nbd_port)
>>                      } }
>> -        self.client_test('nbd://localhost:%i' % NBD_PORT,
>> +        self.client_test('nbd://localhost:%i' % nbd_port,
>>                           flatten_sock_addr(address))
>>  
>>      def test_unix(self):
>> @@ -130,8 +146,13 @@ class BuiltinNBD(NBDBlockdevAddBase):
>>          except OSError:
>>              pass
>>  
>> -    def _server_up(self, address, export_name=None, export_name2=None):
>> +    # Returns False on EADDRINUSE; fails an assertion on other errors.
>> +    # Returns True on success.
>> +    def _try_server_up(self, address, export_name=None, export_name2=None):
>>          result = self.server.qmp('nbd-server-start', addr=address)
>> +        if 'error' in result and \
>> +           'Address already in use' in result['error']['desc']:
>> +            return False
>>          self.assert_qmp(result, 'return', {})
>>  
>>          if export_name is None:
>> @@ -146,20 +167,28 @@ class BuiltinNBD(NBDBlockdevAddBase):
>>                                       name=export_name2)
>>              self.assert_qmp(result, 'return', {})
>>  
>> +        return True
>> +
>> +    def _server_up(self, address, export_name=None, export_name2=None):
>> +        self.assertTrue(self._try_server_up(address, export_name, 
>> export_name2))
>>  
>>      def _server_down(self):
>>          result = self.server.qmp('nbd-server-stop')
>>          self.assert_qmp(result, 'return', {})
>>  
>>      def do_test_inet(self, export_name=None):
>> -        address = { 'type': 'inet',
>> -                    'data': {
>> -                        'host': 'localhost',
>> -                        'port': str(NBD_PORT)
>> -                    } }
>> -        self._server_up(address, export_name)
>> +        while True:
>> +            nbd_port = random.randrange(NBD_PORT_START, NBD_PORT_END)
>> +            address = { 'type': 'inet',
>> +                        'data': {
>> +                            'host': 'localhost',
>> +                            'port': str(nbd_port)
>> +                        } }
>> +            if self._try_server_up(address, export_name):
>> +                break
>> +
>>          export_name = export_name or 'nbd-export'
>> -        self.client_test('nbd://localhost:%i/%s' % (NBD_PORT, export_name),
>> +        self.client_test('nbd://localhost:%i/%s' % (nbd_port, export_name),
>>                           flatten_sock_addr(address), export_name)
>>          self._server_down()
>>  
>> @@ -173,15 +202,19 @@ class BuiltinNBD(NBDBlockdevAddBase):
>>          self.do_test_inet('shadow')
>>  
>>      def test_inet_two_exports(self):
>> -        address = { 'type': 'inet',
>> -                    'data': {
>> -                        'host': 'localhost',
>> -                        'port': str(NBD_PORT)
>> -                    } }
>> -        self._server_up(address, 'exp1', 'exp2')
>> -        self.client_test('nbd://localhost:%i/%s' % (NBD_PORT, 'exp1'),
>> +        while True:
>> +            nbd_port = random.randrange(NBD_PORT_START, NBD_PORT_END)
>> +            address = { 'type': 'inet',
>> +                        'data': {
>> +                            'host': 'localhost',
>> +                            'port': str(nbd_port)
>> +                        } }
>> +            if self._try_server_up(address, 'exp1', 'exp2'):
>> +                break
>> +
>> +        self.client_test('nbd://localhost:%i/%s' % (nbd_port, 'exp1'),
>>                           flatten_sock_addr(address), 'exp1', 'node1', False)
>> -        self.client_test('nbd://localhost:%i/%s' % (NBD_PORT, 'exp2'),
>> +        self.client_test('nbd://localhost:%i/%s' % (nbd_port, 'exp2'),
>>                           flatten_sock_addr(address), 'exp2', 'node2', False)
>>          result = self.vm.qmp('blockdev-del', node_name='node1')
>>          self.assert_qmp(result, 'return', {})
>> @@ -197,20 +230,25 @@ class BuiltinNBD(NBDBlockdevAddBase):
>>          except socket.gaierror:
>>              # IPv6 not available, skip
>>              return
>> -        address = { 'type': 'inet',
>> -                    'data': {
>> -                        'host': '::1',
>> -                        'port': str(NBD_PORT),
>> -                        'ipv4': False,
>> -                        'ipv6': True
>> -                    } }
>> +
>> +        while True:
>> +            nbd_port = random.randrange(NBD_IPV6_PORT_START, 
>> NBD_IPV6_PORT_END)
>> +            address = { 'type': 'inet',
>> +                        'data': {
>> +                            'host': '::1',
>> +                            'port': str(nbd_port),
>> +                            'ipv4': False,
>> +                            'ipv6': True
>> +                        } }
>> +            if self._try_server_up(address):
>> +                break
>> +
>>          filename = { 'driver': 'raw',
>>                       'file': {
>>                           'driver': 'nbd',
>>                           'export': 'nbd-export',
>>                           'server': flatten_sock_addr(address)
>>                       } }
>> -        self._server_up(address)
>>          self.client_test(filename, flatten_sock_addr(address), 'nbd-export')
>>          self._server_down()
>>  
>>
> 
> I guess my only other observation is that we have a lot of "while True"
> loops now, is it worth creating some kind of helper that does the dirty
> work of finding a serviceable port or nah?

Seems reasonable, I'll see how it looks.

> If none of my observations spark joy:
> 
> 1-3: Reviewed-By: John Snow <address@hidden>

Thanks!

Max

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