ssh: fix flakey ssh errors on BSD systems

There's been a persistent issue with flakiness on BSD systems (like OSX) where
the 'no suitable response from remote hg' message would sometimes not appear.
This was caused by one of the earlier calls failing with a "IOError: Broken
pipe". Catching those errors and printing the same message removes the
flakiness.

Differential Revision: https://phab.mercurial-scm.org/D687

mercurial/sshpeer.py

@@ -1,349 +1,359 b''
 # sshpeer.py - ssh repository proxy class for mercurial
 #
 # Copyright 2005, 2006 Matt Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from __future__ import absolute_import
 
 import re
 
 from .i18n import _
 from . import (
     error,
     pycompat,
     util,
     wireproto,
 )
 
 def _serverquote(s):
     if not s:
         return s
     '''quote a string for the remote shell ... which we assume is sh'''
     if re.match('[a-zA-Z0-9@%_+=:,./-]*$', s):
         return s
     return "'%s'" % s.replace("'", "'\\''")
 
 def _forwardoutput(ui, pipe):
     """display all data currently available on pipe as remote output.
 
     This is non blocking."""
     s = util.readpipe(pipe)
     if s:
         for l in s.splitlines():
             ui.status(_("remote: "), l, '\n')
 
 class doublepipe(object):
     """Operate a side-channel pipe in addition of a main one
 
     The side-channel pipe contains server output to be forwarded to the user
     input. The double pipe will behave as the "main" pipe, but will ensure the
     content of the "side" pipe is properly processed while we wait for blocking
     call on the "main" pipe.
 
     If large amounts of data are read from "main", the forward will cease after
     the first bytes start to appear. This simplifies the implementation
     without affecting actual output of sshpeer too much as we rarely issue
     large read for data not yet emitted by the server.
 
     The main pipe is expected to be a 'bufferedinputpipe' from the util module
     that handle all the os specific bits. This class lives in this module
     because it focus on behavior specific to the ssh protocol."""
 
     def __init__(self, ui, main, side):
         self._ui = ui
         self._main = main
         self._side = side
 
     def _wait(self):
         """wait until some data are available on main or side
 
         return a pair of boolean (ismainready, issideready)
 
         (This will only wait for data if the setup is supported by `util.poll`)
         """
         if getattr(self._main, 'hasbuffer', False): # getattr for classic pipe
             return (True, True) # main has data, assume side is worth poking at.
         fds = [self._main.fileno(), self._side.fileno()]
         try:
             act = util.poll(fds)
         except NotImplementedError:
             # non supported yet case, assume all have data.
             act = fds
         return (self._main.fileno() in act, self._side.fileno() in act)
 
     def write(self, data):
         return self._call('write', data)
 
     def read(self, size):
         r = self._call('read', size)
         if size != 0 and not r:
             # We've observed a condition that indicates the
             # stdout closed unexpectedly. Check stderr one
             # more time and snag anything that's there before
             # letting anyone know the main part of the pipe
             # closed prematurely.
             _forwardoutput(self._ui, self._side)
         return r
 
     def readline(self):
         return self._call('readline')
 
     def _call(self, methname, data=None):
         """call <methname> on "main", forward output of "side" while blocking
         """
         # data can be '' or 0
         if (data is not None and not data) or self._main.closed:
             _forwardoutput(self._ui, self._side)
             return ''
         while True:
             mainready, sideready = self._wait()
             if sideready:
                 _forwardoutput(self._ui, self._side)
             if mainready:
                 meth = getattr(self._main, methname)
                 if data is None:
                     return meth()
                 else:
                     return meth(data)
 
     def close(self):
         return self._main.close()
 
     def flush(self):
         return self._main.flush()
 
 class sshpeer(wireproto.wirepeer):
     def __init__(self, ui, path, create=False):
         self._url = path
         self._ui = ui
         self._pipeo = self._pipei = self._pipee = None
 
         u = util.url(path, parsequery=False, parsefragment=False)
         if u.scheme != 'ssh' or not u.host or u.path is None:
             self._abort(error.RepoError(_("couldn't parse location %s") % path))
 
         util.checksafessh(path)
 
         if u.passwd is not None:
             self._abort(error.RepoError(_("password in URL not supported")))
 
         self._user = u.user
         self._host = u.host
         self._port = u.port
         self._path = u.path or '.'
 
         sshcmd = self.ui.config("ui", "ssh")
         remotecmd = self.ui.config("ui", "remotecmd")
 
         args = util.sshargs(sshcmd, self._host, self._user, self._port)
 
         if create:
             cmd = '%s %s %s' % (sshcmd, args,
                 util.shellquote("%s init %s" %
                     (_serverquote(remotecmd), _serverquote(self._path))))
             ui.debug('running %s\n' % cmd)
             res = ui.system(cmd, blockedtag='sshpeer')
             if res != 0:
                 self._abort(error.RepoError(_("could not create remote repo")))
 
         self._validaterepo(sshcmd, args, remotecmd)
 
     # Begin of _basepeer interface.
 
     @util.propertycache
     def ui(self):
         return self._ui
 
     def url(self):
         return self._url
 
     def local(self):
         return None
 
     def peer(self):
         return self
 
     def canpush(self):
         return True
 
     def close(self):
         pass
 
     # End of _basepeer interface.
 
     # Begin of _basewirecommands interface.
 
     def capabilities(self):
         return self._caps
 
     # End of _basewirecommands interface.
 
     def _validaterepo(self, sshcmd, args, remotecmd):
         # cleanup up previous run
         self._cleanup()
 
         cmd = '%s %s %s' % (sshcmd, args,
             util.shellquote("%s -R %s serve --stdio" %
                 (_serverquote(remotecmd), _serverquote(self._path))))
         self.ui.debug('running %s\n' % cmd)
         cmd = util.quotecommand(cmd)
 
         # while self._subprocess isn't used, having it allows the subprocess to
         # to clean up correctly later
         #
         # no buffer allow the use of 'select'
         # feel free to remove buffering and select usage when we ultimately
         # move to threading.
         sub = util.popen4(cmd, bufsize=0)
         self._pipeo, self._pipei, self._pipee, self._subprocess = sub
 
         self._pipei = util.bufferedinputpipe(self._pipei)
         self._pipei = doublepipe(self.ui, self._pipei, self._pipee)
         self._pipeo = doublepipe(self.ui, self._pipeo, self._pipee)
 
-        # skip any noise generated by remote shell
-        self._callstream("hello")
-        r = self._callstream("between", pairs=("%s-%s" % ("0"*40, "0"*40)))
+        def badresponse():
+            self._abort(error.RepoError(_('no suitable response from '
+                                          'remote hg')))
+
+        try:
+            # skip any noise generated by remote shell
+            self._callstream("hello")
+            r = self._callstream("between", pairs=("%s-%s" % ("0"*40, "0"*40)))
+        except IOError:
+            badresponse()
+
         lines = ["", "dummy"]
         max_noise = 500
         while lines[-1] and max_noise:
-            l = r.readline()
-            self._readerr()
-            if lines[-1] == "1\n" and l == "\n":
-                break
-            if l:
-                self.ui.debug("remote: ", l)
-            lines.append(l)
-            max_noise -= 1
+            try:
+                l = r.readline()
+                self._readerr()
+                if lines[-1] == "1\n" and l == "\n":
+                    break
+                if l:
+                    self.ui.debug("remote: ", l)
+                lines.append(l)
+                max_noise -= 1
+            except IOError:
+                badresponse()
         else:
-            self._abort(error.RepoError(_('no suitable response from '
-                                          'remote hg')))
+            badresponse()
 
         self._caps = set()
         for l in reversed(lines):
             if l.startswith("capabilities:"):
                 self._caps.update(l[:-1].split(":")[1].split())
                 break
 
     def _readerr(self):
         _forwardoutput(self.ui, self._pipee)
 
     def _abort(self, exception):
         self._cleanup()
         raise exception
 
     def _cleanup(self):
         if self._pipeo is None:
             return
         self._pipeo.close()
         self._pipei.close()
         try:
             # read the error descriptor until EOF
             for l in self._pipee:
                 self.ui.status(_("remote: "), l)
         except (IOError, ValueError):
             pass
         self._pipee.close()
 
     __del__ = _cleanup
 
     def _submitbatch(self, req):
         rsp = self._callstream("batch", cmds=wireproto.encodebatchcmds(req))
         available = self._getamount()
         # TODO this response parsing is probably suboptimal for large
         # batches with large responses.
         toread = min(available, 1024)
         work = rsp.read(toread)
         available -= toread
         chunk = work
         while chunk:
             while ';' in work:
                 one, work = work.split(';', 1)
                 yield wireproto.unescapearg(one)
             toread = min(available, 1024)
             chunk = rsp.read(toread)
             available -= toread
             work += chunk
         yield wireproto.unescapearg(work)
 
     def _callstream(self, cmd, **args):
         args = pycompat.byteskwargs(args)
         self.ui.debug("sending %s command\n" % cmd)
         self._pipeo.write("%s\n" % cmd)
         _func, names = wireproto.commands[cmd]
         keys = names.split()
         wireargs = {}
         for k in keys:
             if k == '*':
                 wireargs['*'] = args
                 break
             else:
                 wireargs[k] = args[k]
                 del args[k]
         for k, v in sorted(wireargs.iteritems()):
             self._pipeo.write("%s %d\n" % (k, len(v)))
             if isinstance(v, dict):
                 for dk, dv in v.iteritems():
                     self._pipeo.write("%s %d\n" % (dk, len(dv)))
                     self._pipeo.write(dv)
             else:
                 self._pipeo.write(v)
         self._pipeo.flush()
 
         return self._pipei
 
     def _callcompressable(self, cmd, **args):
         return self._callstream(cmd, **args)
 
     def _call(self, cmd, **args):
         self._callstream(cmd, **args)
         return self._recv()
 
     def _callpush(self, cmd, fp, **args):
         r = self._call(cmd, **args)
         if r:
             return '', r
         for d in iter(lambda: fp.read(4096), ''):
             self._send(d)
         self._send("", flush=True)
         r = self._recv()
         if r:
             return '', r
         return self._recv(), ''
 
     def _calltwowaystream(self, cmd, fp, **args):
         r = self._call(cmd, **args)
         if r:
             # XXX needs to be made better
             raise error.Abort(_('unexpected remote reply: %s') % r)
         for d in iter(lambda: fp.read(4096), ''):
             self._send(d)
         self._send("", flush=True)
         return self._pipei
 
     def _getamount(self):
         l = self._pipei.readline()
         if l == '\n':
             self._readerr()
             msg = _('check previous remote output')
             self._abort(error.OutOfBandError(hint=msg))
         self._readerr()
         try:
             return int(l)
         except ValueError:
             self._abort(error.ResponseError(_("unexpected response:"), l))
 
     def _recv(self):
         return self._pipei.read(self._getamount())
 
     def _send(self, data, flush=False):
         self._pipeo.write("%d\n" % len(data))
         if data:
             self._pipeo.write(data)
         if flush:
             self._pipeo.flush()
         self._readerr()
 
 instance = sshpeer