hgext/inotify/client.py

inotify: Separate query sending logic from Server starting.

Use a decorator around the public statusquery method of Client:

start_server(query_to_server):
    try:
        query_to_server()
    except QueryFailed:
        [error recovery, inotify Server (re)starting]
        query_to_server()

This way, introducing a new xxxquery Client method is easy:
one has only to code the protocol part of xxxquery, ignoring errors,
and decorating it using start_server to handle server recovery
and (re)starts

# client.py - inotify status client
#
# Copyright 2006, 2007, 2008 Bryan O'Sullivan <[e-mail]>
# Copyright 2007, 2008 Brendan Cully <[e-mail]>
# Copyright 2009 Nicolas Dumazet <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2, incorporated herein by reference.

from mercurial.i18n import _
import common, server
import errno, os, socket, struct

class QueryFailed(Exception): pass

def start_server(function):
    """
    Decorator.
    Tries to call function, if it fails, try to (re)start inotify server.
    Raise QueryFailed if something went wrong
    """
    def decorated_function(self, *args):
        result = None
        try:
            return function(self, *args)
        except (OSError, socket.error), err:
            autostart = self.ui.configbool('inotify', 'autostart', True)

            if err[0] == errno.ECONNREFUSED:
                self.ui.warn(_('(found dead inotify server socket; '
                               'removing it)\n'))
                os.unlink(self.repo.join('inotify.sock'))
            if err[0] in (errno.ECONNREFUSED, errno.ENOENT) and autostart:
                self.ui.debug(_('(starting inotify server)\n'))
                try:
                    try:
                        server.start(self.ui, self.repo)
                    except server.AlreadyStartedException, inst:
                        # another process may have started its own
                        # inotify server while this one was starting.
                        self.ui.debug(str(inst))
                except Exception, inst:
                    self.ui.warn(_('could not start inotify server: '
                                   '%s\n') % inst)
                else:
                    try:
                        return function(self, *args)
                    except socket.error, err:
                        self.ui.warn(_('could not talk to new inotify '
                                       'server: %s\n') % err[-1])
            elif err[0] in (errno.ECONNREFUSED, errno.ENOENT):
                # silently ignore normal errors if autostart is False
                self.ui.debug(_('(inotify server not running)\n'))
            else:
                self.ui.warn(_('failed to contact inotify server: %s\n')
                         % err[-1])

        self.ui.traceback()
        raise QueryFailed('inotify query failed')

    return decorated_function


class client(object):
    def __init__(self, ui, repo):
        self.ui = ui
        self.repo = repo
        self.sock = socket.socket(socket.AF_UNIX)

    def _connect(self):
        sockpath = self.repo.join('inotify.sock')
        try:
            self.sock.connect(sockpath)
        except socket.error, err:
            if err[0] == "AF_UNIX path too long":
                sockpath = os.readlink(sockpath)
                self.sock.connect(sockpath)
            else:
                raise

    def _send(self, data):
        """Sends protocol version number, and the data"""
        self.sock.sendall(chr(common.version) + data)

        self.sock.shutdown(socket.SHUT_WR)

    def _receive(self):
        """
        Read data, check version number, extract headers,
        and returns a tuple (data descriptor, header)
        Raises QueryFailed on error
        """
        cs = common.recvcs(self.sock)
        version = ord(cs.read(1))
        if version != common.version:
            self.ui.warn(_('(inotify: received response from incompatible '
                      'server version %d)\n') % version)
            raise QueryFailed('incompatible server version')

        # only one type of request is supported for now
        type = 'STAT'
        hdrfmt = common.resphdrfmts[type]
        hdrsize = common.resphdrsizes[type]
        try:
            resphdr = struct.unpack(hdrfmt, cs.read(hdrsize))
        except struct.error:
            raise QueryFailed('unable to retrieve query response headers')

        return cs, resphdr

    def query(self, req):
        self._connect()

        self._send(req)

        return self._receive()

    @start_server
    def statusquery(self, names, match, ignored, clean, unknown=True):

        def genquery():
            for n in names:
                yield n
            states = 'almrx!'
            if ignored:
                raise ValueError('this is insanity')
            if clean: states += 'c'
            if unknown: states += '?'
            yield states

        req = '\0'.join(genquery())

        cs, resphdr = self.query(req)

        def readnames(nbytes):
            if nbytes:
                names = cs.read(nbytes)
                if names:
                    return filter(match, names.split('\0'))
            return []

        return map(readnames, resphdr)