Add Windows support

[amigo00678]

Running 'python -m pip install asyncpg' causes an error on Windows:
`
running build_ext
building 'asyncpg.protocol.protocol' extension
creating build\temp.win32-3.5
creating build\temp.win32-3.5\Release
creating build\temp.win32-3.5\Release\asyncpg
creating build\temp.win32-3.5\Release\asyncpg\protocol
creating build\temp.win32-3.5\Release\asyncpg\protocol\record
C:\Program Files\Microsoft Visual Studio 14.0\VC\BIN\cl.exe /c /nologo /Ox /
W3 /GL /DNDEBUG /MD -IC:\Python35\include -IC:\Python35\include "-IC:\Program Files\Microsoft Visual Studio 14.0\VC\INCLUDE" "-IC:\Program Files\Windows Kits\10\include\10.0.10240.0\ucrt" "-IC:\Program Files\Windows Kits\8.1\include\shared" "-IC:\Program Files\Windows Kits\8.1\include\um" "-IC:\Program Files\Windows Kits\8.1\include\winrt" /Tcasyncpg/protocol/record/recordobj.c Fobuild\temp.win32-3.5\Release\asyncpg/protocol/record/recordobj.obj -O2
recordobj.c
C:\Program Files\Microsoft Visual Studio 14.0\VC\BIN\cl.exe /c /nologo /Ox /W3 /GL /DNDEBUG /MD -IC:\Python35\include -IC:\Python35\include "-IC:\Program Files\Microsoft Visual Studio 14.0\VC\INCLUDE" "-IC:\Program Files\Windows Kits\10\include\10.0.10240.0\ucrt" "-IC:\Program Files\Windows Kits\8.1\include\shared" "-IC:\Program Files\Windows Kits\8.1\include\um" "-IC:\Program Files\Windows Kits\8.1\include\winrt" /Tcasyncpg/protocol/protocol.c /Fobuild\temp.win32-3.5\Rel
ease\asyncpg/protocol/protocol.obj -O2
protocol.c
asyncpg/protocol/protocol.c(276): fatal error C1083: Cannot open include file: 'arpa/inet.h': No such file or directory
error: command 'C:\Program Files\Microsoft Visual Studio 14.0\VC\BIN\cl.exe' failed with exit status 2

[espositofulvio]

This is because asyncpg is not supported on windows. I've got a separate branch here https://github.com/espositofulvio/asyncpg/tree/windows which allows me to compile the extension and run a simple test

import asyncio
import asyncpg

async def init_app():
    connection = await asyncpg.connect(host='127.0.0.1', database='postgres', user='postgres', password='postgres' )
    async with connection.transaction():
        res = await connection.fetchval( 'select 2 ^ 5' )
        print( 'result is {0}'.format( res ) )

loop = asyncio.get_event_loop()
app = loop.run_until_complete(init_app())

But 99 tests out of 103 fail with the error "cluster is not running". I'm not sure what Cluster represents as I can find usages only in tests. Maybe someone from the core team can explain so I can try and make all tests pass on Windows as well.

[elprans]

There are some issues with starting the Postgres cluster on Windows that fails the tests. I haven't really looked into what exactly is wrong, but you can probably get that by putting subprocess.PIPE here.

[espositofulvio]

There are some issues with starting the Postgres cluster on Windows that fails the tests. I haven't really looked into what exactly is wrong, but you can probably get that by putting subprocess.PIPE here.

I've also got to conditionally add the local entry in pg_hba.conf because it doesn't work on windows and add an entry for "::1/128" as well.
I've reduced the failing tests to 34, most of which are:

ConnectionResetError: [WinError 10054] An existing connection was forcibly closed by the remote host

Any hunch what might cause that?

[espositofulvio]

This is the first error from tests:

ERROR:  canceling statement due to user request                                                                                                                                                                                               
STATEMENT:  SELECT pg_sleep(20)                                                                                                                                                                                                               
Task exception was never retrieved                                                                                                                                                                                                            
future: <Task finished coro=<Connection._cancel_current_command.<locals>.cancel() done, defined at d:\Work\Lasco\asyncpg\asyncpg\connection.py:388> exception=InvalidStateError("FINISHED: <Future finished exception=ConnectionResetError(100
54, 'An existing connection was forcibly closed by the remote host', None, 10054, None) created at D:\\Programs\\Python\\lib\\asyncio\\base_events.py:252>",) created at d:\Work\Lasco\asyncpg\asyncpg\connection.py:419>                     
source_traceback: Object created at (most recent call last):                                                                                                                                                                                  
  File "D:\Programs\Python\lib\runpy.py", line 184, in _run_module_as_main                                                                                                                                                                    
    "__main__", mod_spec)                                                                                                                                                                                                                     
  File "D:\Programs\Python\lib\runpy.py", line 85, in _run_code                                                                                                                                                                               
    exec(code, run_globals)                                                                                                                                                                                                                   
  File "D:\Programs\Python\lib\unittest\__main__.py", line 18, in <module>                                                                                                                                                                    
    main(module=None)                                                                                                                                                                                                                         
  File "D:\Programs\Python\lib\unittest\main.py", line 94, in __init__                                                                                                                                                                        
    self.runTests()                                                                                                                                                                                                                           
  File "D:\Programs\Python\lib\unittest\main.py", line 255, in runTests                                                                                                                                                                       
    self.result = testRunner.run(self.test)                                                                                                                                                                                                   
  File "D:\Programs\Python\lib\unittest\runner.py", line 176, in run                                                                                                                                                                          
    test(result)                                                                                                                                                                                                                              
  File "D:\Programs\Python\lib\unittest\suite.py", line 84, in __call__                                                                                                                                                                       
    return self.run(*args, **kwds)                                                                                                                                                                                                            
  File "D:\Programs\Python\lib\unittest\suite.py", line 122, in run                                                                                                                                                                           
    test(result)                                                                                                                                                                                                                              
  File "D:\Programs\Python\lib\unittest\suite.py", line 84, in __call__                                                                                                                                                                       
    return self.run(*args, **kwds)                                                                                                                                                                                                            
  File "D:\Programs\Python\lib\unittest\suite.py", line 122, in run                                                                                                                                                                           
    test(result)                                                                                                                                                                                                                              
  File "D:\Programs\Python\lib\unittest\suite.py", line 84, in __call__                                                                                                                                                                       
    return self.run(*args, **kwds)                                                                                                                                                                                                            
  File "D:\Programs\Python\lib\unittest\suite.py", line 122, in run                                                                                                                                                                           
    test(result)                                                                                                                                                                                                                              
  File "D:\Programs\Python\lib\unittest\case.py", line 648, in __call__                                                                                                                                                                       
    return self.run(*args, **kwds)                                                                                                                                                                                                            
  File "D:\Programs\Python\lib\unittest\case.py", line 600, in run                                                                                                                                                                            
    testMethod()                                                                                                                                                                                                                              
  File "d:\Work\Lasco\asyncpg\asyncpg\_testbase.py", line 65, in wrapper                                                                                                                                                                      
    self.loop.run_until_complete(__meth__(self, *args, **kwargs))                                                                                                                                                                             
  File "D:\Programs\Python\lib\asyncio\base_events.py", line 375, in run_until_complete                                                                                                                                                       
    self.run_forever()                                                                                                                                                                                                                        
  File "D:\Programs\Python\lib\asyncio\base_events.py", line 345, in run_forever                                                                                                                                                              
    self._run_once()                                                                                                                                                                                                                          
  File "D:\Programs\Python\lib\asyncio\base_events.py", line 1304, in _run_once                                                                                                                                                               
    handle._run()                                                                                                                                                                                                                             
  File "D:\Programs\Python\lib\asyncio\events.py", line 125, in _run                                                                                                                                                                          
    self._callback(*self._args)                                                                                                                                                                                                               
  File "d:\Work\Lasco\asyncpg\asyncpg\connection.py", line 419, in _cancel_current_command                                                                                                                                                    
    self._loop.create_task(cancel())    

[nursike]

@espositofulvio @amigo00678 I have the same problem with asyncpg on Windows. Did you figure out how to solve this issue?

[espositofulvio]

@Nursik91 unfortunately not yet. It's not very clear to me, I had a look at a couple of cases and I couldn't find a reason as to why that exceptions are thrown. It looks like await is not called on the future but I can actually see it in the test case, so I'm dead in the water. If you want to try it by yourself, have a look at https://github.com/espositofulvio/asyncpg/tree/windows where I'm developing windows support. I'm using cmder as shell, but make is not supported so I had to type each build command to compile the extension, you need VisualC++ 2015 installed by the way.

By the way, I've also tried switching to a ProactorLoopEvent as it is suggested for higher performance, but then there are loads of exceptions so I won't recommend using asyncpg in production on Windows until uvloop by MagickStack is ported to Windows as well.

[espositofulvio]

@elprans by the way, is there an internal effort at MagickStack to support Windows? I mean for uvloop and asyncpg mainly.

[elprans]

@espositofulvio I will try to look into asyncpg Windows issues this week.

[1st1]

Closing this issue now.