git-remote-fd problem

git-remote-fd problem

[Jiri Sevcik]

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Hi!
I have problem with using git-remote-fd function. I create two local
pipes for communication for locally running process git pull. Then I
start git-upload-pack on remote side (this process is started in
different part of my code  and it works correctly). Communication runs
successfully and when remote side finish, I want to close local pipes
to finish local process. I call close function to all of these pipes,
but unfortunatelly local process doesnt finish (in this moment
transfered data aresaved in /.git/object/pack folder in .pack files)
and hanging on. But if I kill child of this local process, downloaded
files are unpacked and files are created sucessfully. I think this way
is not so correct. Can someone help me and tell me what am I doing
wrong? Thank You. Code is in an attachement (its part of big system).

[-- Attachment #2: git_remote.py --]
[-- Type: text/x-python, Size: 2644 bytes --]

    #create local pipes for cimmunication
    local_r, local_w = os.pipe()
    remote_r, remote_w = os.pipe()

    #start local git process
    client_process = subprocess.Popen("/usr/bin/git pull fd::{0},{1}".format(remote_r, local_w,), shell=True)
    
    #start git process on remote side 
    remoteGit = proc.runDaemon("sudo git-upload-pack /tmp/testGit")

    #set
    epoll = select.epoll()

    epoll.register(local_r, select.EPOLLIN)
    #register from remote side
    epoll.register(proc.fd, select.EPOLLIN)

    while True:
        events = epoll.poll(1)

        for fd, event in events:
            if fd == local_r:
                #event on local process
                if event & select.EPOLLIN:
                    rd = os.read(local_r, 5000)

                    if rd:
                        #write data to remote side
                        remoteGit.writeToChannel(rd)
                    else:
                        proc.writeError("Local socket write error")
                        client_process.kill()
                        return 1
                else:
                    proc.writeError("Local socket error")
                    client_process.kill()
                    return 1

            else:
                if event & select.EPOLLIN:
                    #get all data from remote side
                    data = remoteGit.getAll()
                    remoteGit.stderrWrite()

                    if not data:
                        #remote side finished - close local pipes - local process wouldnt finish 
                        os.close(local_r) 
                        os.close(local_w)
                        os.close(remote_r)
                        os.close(remote_w)

                        #get local process pid and kill his child to finish git-remote-fd
                        gitPid = psutil.Process(client_process.pid).children()[0].pid
                        os.kill(gitPid, signal.SIGTERM)

                        return 0


                    want = len(data)
                    writed = 0
                    offset = 0

                    while(writed != want):
                        #write data from remote side to local process
                        wr = os.write(remote_w, data[offset:])

                        if(wr < 0):
                            proc.writeError("Local socket write error")

                            return 1

                        writed += wr
                        offset += wr

                else:
                    proc.writeError("Remote socket error")
                    client_process.kill()
                    return -1

Re: git-remote-fd problem

[Ilari Liusvaara]

On Wed, Sep 10, 2014 at 03:29:00PM +0200, Jiri Sevcik wrote:
> Hi!
> I have problem with using git-remote-fd function. I create two local
> pipes for communication for locally running process git pull. Then I
> start git-upload-pack on remote side (this process is started in
> different part of my code  and it works correctly). Communication runs
> successfully and when remote side finish, I want to close local pipes
> to finish local process. I call close function to all of these pipes,
> but unfortunatelly local process doesnt finish (in this moment
> transfered data aresaved in /.git/object/pack folder in .pack files)
> and hanging on. But if I kill child of this local process, downloaded
> files are unpacked and files are created sucessfully. I think this way
> is not so correct. Can someone help me and tell me what am I doing
> wrong? Thank You. Code is in an attachement (its part of big system).

The remote-fd expects the transport to pass half-closes. So you can't
close all at once.

Let there be pipes W and R and transport connection C.

- W-read should be closed after being passed to remote-fd.
- R-write should be closed after being passed to remote-fd.
- Upon receiving "no more data" from C, close W-write.
- Upon receiving EOF from R-read, close it and signal "no more data"
  to C.

If you have server end, the same applies, but with remote-fd replaced
by upload-pack/upload-archive/receive-pack.


-Ilari

Fwd: git-remote-fd problem

[Jiri Sevcik]

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> The remote-fd expects the transport to pass half-closes. So you can't
> close all at once.
>
> Let there be pipes W and R and transport connection C.
>
> - W-read should be closed after being passed to remote-fd.
> - R-write should be closed after being passed to remote-fd.
> - Upon receiving "no more data" from C, close W-write.
> - Upon receiving EOF from R-read, close it and signal "no more data"
>   to C.

Hi, I followed your advices, correctly close pipes but git clone still
doesnt finish and hanging on.
Code is in an attachement (its part of big system).

[-- Attachment #2: git_test_improved.py --]
[-- Type: text/x-python, Size: 2018 bytes --]


    #create pipes
    w_pipe = os.pipe()
    r_pipe = os.pipe()

    client_process = subprocess.Popen("/usr/bin/git clone fd::{0},{1} /tmp/gittest".format(r_pipe[0], w_pipe[1]), shell=True)
    #closing pipes
    os.close(r_pipe[0]) 
    os.close(w_pipe[1])

    epoll = select.epoll()
    epoll.register(w_pipe[0], select.EPOLLIN)
    epoll.register(proc.fd, select.EPOLLIN)

    remoteGit = proc.runDaemon("git-upload-pack /tmp/testgit")
    
    while True:
        events = epoll.poll(1)

        for fd, event in events:
            if fd == w_pipe[0]:
                if event & select.EPOLLIN:
                    rd = os.read(w_pipe[0], 10000)
                    if rd:
                        #write data to remove git server
                        remoteGit.writeToChannel(rd)
                    else:
                        proc.writeError("Local socket write error")
                        return 1
                else:
                    proc.writeError("Local socket error")
                    return 1

            elif fd == proc.fd:
                if event & select.EPOLLIN:
                    #read data from remote git server
                    data = remoteGit.getAll()
                    remoteGit.stderrWrite()

                    if not data:
                        #remote server send EOF, close local pipe
                        #but git clone is still running
                        os.close(r_pipe[1])
                        return 0
                    
                    want = len(data)

                    writed = 0
                    offset = 0
                    
                    while(writed != want):
                        #write data from remote git server to local pipe
                        wr = os.write(r_pipe[1], data[offset:])

                        if(wr < 0):
                            return 1

                        writed += wr
                        offset += wr

                else:
                    return -1              

Re: Fwd: git-remote-fd problem

[Ilari Liusvaara]

On Mon, Dec 29, 2014 at 10:47:58AM +0100, Jiri Sevcik wrote:
> > The remote-fd expects the transport to pass half-closes. So you can't
> > close all at once.
> >
> > Let there be pipes W and R and transport connection C.
> >
> > - W-read should be closed after being passed to remote-fd.
> > - R-write should be closed after being passed to remote-fd.
> > - Upon receiving "no more data" from C, close W-write.
> > - Upon receiving EOF from R-read, close it and signal "no more data"
> >   to C.
> 
> Hi, I followed your advices, correctly close pipes but git clone still
> doesnt finish and hanging on.
> Code is in an attachement (its part of big system).

Few ideas:
- Check that git clone (and its subprocesses) don't inherit
w_pipe[0] (/proc/<pid>/fd on Linux might be handy). If they do, that
prevents this program from closing the pipe.

- Setting environment variable GIT_TRANSLOOP_DEBUG to 1 might make
  git spew lots of messages to stderr about reads, writes and closes.

> 
>     #create pipes
>     w_pipe = os.pipe()
>     r_pipe = os.pipe()
> 
>     client_process = subprocess.Popen("/usr/bin/git clone fd::{0},{1} /tmp/gittest".format(r_pipe[0], w_pipe[1]), shell=True)
>     #closing pipes
>     os.close(r_pipe[0]) 
>     os.close(w_pipe[1])
> 
>     epoll = select.epoll()
>     epoll.register(w_pipe[0], select.EPOLLIN)
>     epoll.register(proc.fd, select.EPOLLIN)
> 
>     remoteGit = proc.runDaemon("git-upload-pack /tmp/testgit")
>     
>     while True:
>         events = epoll.poll(1)
> 
>         for fd, event in events:
>             if fd == w_pipe[0]:
>                 if event & select.EPOLLIN:
>                     rd = os.read(w_pipe[0], 10000)
>                     if rd:
>                         #write data to remove git server
>                         remoteGit.writeToChannel(rd)
>                     else:
>                         proc.writeError("Local socket write error")
>                         return 1
>                 else:
>                     proc.writeError("Local socket error")
>                     return 1
> 
>             elif fd == proc.fd:
>                 if event & select.EPOLLIN:
>                     #read data from remote git server
>                     data = remoteGit.getAll()
>                     remoteGit.stderrWrite()
> 
>                     if not data:
>                         #remote server send EOF, close local pipe
>                         #but git clone is still running
>                         os.close(r_pipe[1])
>                         return 0
>                     
>                     want = len(data)
> 
>                     writed = 0
>                     offset = 0
>                     
>                     while(writed != want):
>                         #write data from remote git server to local pipe
>                         wr = os.write(r_pipe[1], data[offset:])
> 
>                         if(wr < 0):
>                             return 1
> 
>                         writed += wr
>                         offset += wr
> 
>                 else:
>                     return -1              

-Ilari