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

[John Snow]

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.

> +        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?

> +
>          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?


If none of my observations spark joy:

1-3: Reviewed-By: John Snow <address@hidden>