Mercurial > hg
view mercurial/commandserver.py @ 39559:07b58266bce3
wireprotov2: implement commands as a generator of objects
Previously, wire protocol version 2 inherited version 1's model of
having separate types to represent the results of different wire
protocol commands.
As I implemented more powerful commands in future commits, I found
I was using a common pattern of returning a special type to hold a
generator. This meant the command function required a closure to
do most of the work. That made logic flow more difficult to follow.
I also noticed that many commands were effectively a sequence of
objects to be CBOR encoded.
I think it makes sense to define version 2 commands as generators.
This way, commands can simply emit the data structures they wish to
send to the client. This eliminates the need for a closure in
command functions and removes encoding from the bodies of commands.
As part of this commit, the handling of response objects has been
moved into the serverreactor class. This puts the reactor in the
driver's seat with regards to CBOR encoding and error handling.
Having error handling in the function that emits frames is
particularly important because exceptions in that function can lead
to things getting in a bad state: I'm fairly certain that uncaught
exceptions in the frame generator were causing deadlocks.
I also introduced a dedicated error type for explicit error reporting
in command handlers. This will be used in subsequent commits.
There's still a bit of work to be done here, especially around
formalizing the error handling "protocol." I've added yet another
TODO to track this so we don't forget.
Test output changed because we're using generators and no longer know
we are at the end of the data until we hit the end of the generator.
This means we can't emit the end-of-stream flag until we've exhausted
the generator. Hence the introduction of 0-sized end-of-stream frames.
Differential Revision: https://phab.mercurial-scm.org/D4472
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Wed, 05 Sep 2018 09:06:40 -0700 |
parents | afc4ad706f9c |
children | 24e493ec2229 |
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# commandserver.py - communicate with Mercurial's API over a pipe # # Copyright Matt Mackall <mpm@selenic.com> # # 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 errno import gc import os import random import signal import socket import struct import traceback try: import selectors selectors.BaseSelector except ImportError: from .thirdparty import selectors2 as selectors from .i18n import _ from . import ( encoding, error, pycompat, util, ) from .utils import ( procutil, ) logfile = None def log(*args): if not logfile: return for a in args: logfile.write(str(a)) logfile.flush() class channeledoutput(object): """ Write data to out in the following format: data length (unsigned int), data """ def __init__(self, out, channel): self.out = out self.channel = channel @property def name(self): return '<%c-channel>' % self.channel def write(self, data): if not data: return # single write() to guarantee the same atomicity as the underlying file self.out.write(struct.pack('>cI', self.channel, len(data)) + data) self.out.flush() def __getattr__(self, attr): if attr in ('isatty', 'fileno', 'tell', 'seek'): raise AttributeError(attr) return getattr(self.out, attr) class channeledinput(object): """ Read data from in_. Requests for input are written to out in the following format: channel identifier - 'I' for plain input, 'L' line based (1 byte) how many bytes to send at most (unsigned int), The client replies with: data length (unsigned int), 0 meaning EOF data """ maxchunksize = 4 * 1024 def __init__(self, in_, out, channel): self.in_ = in_ self.out = out self.channel = channel @property def name(self): return '<%c-channel>' % self.channel def read(self, size=-1): if size < 0: # if we need to consume all the clients input, ask for 4k chunks # so the pipe doesn't fill up risking a deadlock size = self.maxchunksize s = self._read(size, self.channel) buf = s while s: s = self._read(size, self.channel) buf += s return buf else: return self._read(size, self.channel) def _read(self, size, channel): if not size: return '' assert size > 0 # tell the client we need at most size bytes self.out.write(struct.pack('>cI', channel, size)) self.out.flush() length = self.in_.read(4) length = struct.unpack('>I', length)[0] if not length: return '' else: return self.in_.read(length) def readline(self, size=-1): if size < 0: size = self.maxchunksize s = self._read(size, 'L') buf = s # keep asking for more until there's either no more or # we got a full line while s and s[-1] != '\n': s = self._read(size, 'L') buf += s return buf else: return self._read(size, 'L') def __iter__(self): return self def next(self): l = self.readline() if not l: raise StopIteration return l def __getattr__(self, attr): if attr in ('isatty', 'fileno', 'tell', 'seek'): raise AttributeError(attr) return getattr(self.in_, attr) class server(object): """ Listens for commands on fin, runs them and writes the output on a channel based stream to fout. """ def __init__(self, ui, repo, fin, fout): self.cwd = pycompat.getcwd() # developer config: cmdserver.log logpath = ui.config("cmdserver", "log") if logpath: global logfile if logpath == '-': # write log on a special 'd' (debug) channel logfile = channeledoutput(fout, 'd') else: logfile = open(logpath, 'a') if repo: # the ui here is really the repo ui so take its baseui so we don't # end up with its local configuration self.ui = repo.baseui self.repo = repo self.repoui = repo.ui else: self.ui = ui self.repo = self.repoui = None self.cerr = channeledoutput(fout, 'e') self.cout = channeledoutput(fout, 'o') self.cin = channeledinput(fin, fout, 'I') self.cresult = channeledoutput(fout, 'r') self.client = fin def cleanup(self): """release and restore resources taken during server session""" def _read(self, size): if not size: return '' data = self.client.read(size) # is the other end closed? if not data: raise EOFError return data def _readstr(self): """read a string from the channel format: data length (uint32), data """ length = struct.unpack('>I', self._read(4))[0] if not length: return '' return self._read(length) def _readlist(self): """read a list of NULL separated strings from the channel""" s = self._readstr() if s: return s.split('\0') else: return [] def runcommand(self): """ reads a list of \0 terminated arguments, executes and writes the return code to the result channel """ from . import dispatch # avoid cycle args = self._readlist() # copy the uis so changes (e.g. --config or --verbose) don't # persist between requests copiedui = self.ui.copy() uis = [copiedui] if self.repo: self.repo.baseui = copiedui # clone ui without using ui.copy because this is protected repoui = self.repoui.__class__(self.repoui) repoui.copy = copiedui.copy # redo copy protection uis.append(repoui) self.repo.ui = self.repo.dirstate._ui = repoui self.repo.invalidateall() for ui in uis: ui.resetstate() # any kind of interaction must use server channels, but chg may # replace channels by fully functional tty files. so nontty is # enforced only if cin is a channel. if not util.safehasattr(self.cin, 'fileno'): ui.setconfig('ui', 'nontty', 'true', 'commandserver') req = dispatch.request(args[:], copiedui, self.repo, self.cin, self.cout, self.cerr) try: ret = dispatch.dispatch(req) & 255 self.cresult.write(struct.pack('>i', int(ret))) finally: # restore old cwd if '--cwd' in args: os.chdir(self.cwd) def getencoding(self): """ writes the current encoding to the result channel """ self.cresult.write(encoding.encoding) def serveone(self): cmd = self.client.readline()[:-1] if cmd: handler = self.capabilities.get(cmd) if handler: handler(self) else: # clients are expected to check what commands are supported by # looking at the servers capabilities raise error.Abort(_('unknown command %s') % cmd) return cmd != '' capabilities = {'runcommand': runcommand, 'getencoding': getencoding} def serve(self): hellomsg = 'capabilities: ' + ' '.join(sorted(self.capabilities)) hellomsg += '\n' hellomsg += 'encoding: ' + encoding.encoding hellomsg += '\n' hellomsg += 'pid: %d' % procutil.getpid() if util.safehasattr(os, 'getpgid'): hellomsg += '\n' hellomsg += 'pgid: %d' % os.getpgid(0) # write the hello msg in -one- chunk self.cout.write(hellomsg) try: while self.serveone(): pass except EOFError: # we'll get here if the client disconnected while we were reading # its request return 1 return 0 class pipeservice(object): def __init__(self, ui, repo, opts): self.ui = ui self.repo = repo def init(self): pass def run(self): ui = self.ui # redirect stdio to null device so that broken extensions or in-process # hooks will never cause corruption of channel protocol. with procutil.protectedstdio(ui.fin, ui.fout) as (fin, fout): try: sv = server(ui, self.repo, fin, fout) return sv.serve() finally: sv.cleanup() def _initworkerprocess(): # use a different process group from the master process, in order to: # 1. make the current process group no longer "orphaned" (because the # parent of this process is in a different process group while # remains in a same session) # according to POSIX 2.2.2.52, orphaned process group will ignore # terminal-generated stop signals like SIGTSTP (Ctrl+Z), which will # cause trouble for things like ncurses. # 2. the client can use kill(-pgid, sig) to simulate terminal-generated # SIGINT (Ctrl+C) and process-exit-generated SIGHUP. our child # processes like ssh will be killed properly, without affecting # unrelated processes. os.setpgid(0, 0) # change random state otherwise forked request handlers would have a # same state inherited from parent. random.seed() def _serverequest(ui, repo, conn, createcmdserver): fin = conn.makefile('rb') fout = conn.makefile('wb') sv = None try: sv = createcmdserver(repo, conn, fin, fout) try: sv.serve() # handle exceptions that may be raised by command server. most of # known exceptions are caught by dispatch. except error.Abort as inst: ui.error(_('abort: %s\n') % inst) except IOError as inst: if inst.errno != errno.EPIPE: raise except KeyboardInterrupt: pass finally: sv.cleanup() except: # re-raises # also write traceback to error channel. otherwise client cannot # see it because it is written to server's stderr by default. if sv: cerr = sv.cerr else: cerr = channeledoutput(fout, 'e') traceback.print_exc(file=cerr) raise finally: fin.close() try: fout.close() # implicit flush() may cause another EPIPE except IOError as inst: if inst.errno != errno.EPIPE: raise class unixservicehandler(object): """Set of pluggable operations for unix-mode services Almost all methods except for createcmdserver() are called in the main process. You can't pass mutable resource back from createcmdserver(). """ pollinterval = None def __init__(self, ui): self.ui = ui def bindsocket(self, sock, address): util.bindunixsocket(sock, address) sock.listen(socket.SOMAXCONN) self.ui.status(_('listening at %s\n') % address) self.ui.flush() # avoid buffering of status message def unlinksocket(self, address): os.unlink(address) def shouldexit(self): """True if server should shut down; checked per pollinterval""" return False def newconnection(self): """Called when main process notices new connection""" def createcmdserver(self, repo, conn, fin, fout): """Create new command server instance; called in the process that serves for the current connection""" return server(self.ui, repo, fin, fout) class unixforkingservice(object): """ Listens on unix domain socket and forks server per connection """ def __init__(self, ui, repo, opts, handler=None): self.ui = ui self.repo = repo self.address = opts['address'] if not util.safehasattr(socket, 'AF_UNIX'): raise error.Abort(_('unsupported platform')) if not self.address: raise error.Abort(_('no socket path specified with --address')) self._servicehandler = handler or unixservicehandler(ui) self._sock = None self._oldsigchldhandler = None self._workerpids = set() # updated by signal handler; do not iterate self._socketunlinked = None def init(self): self._sock = socket.socket(socket.AF_UNIX) self._servicehandler.bindsocket(self._sock, self.address) if util.safehasattr(procutil, 'unblocksignal'): procutil.unblocksignal(signal.SIGCHLD) o = signal.signal(signal.SIGCHLD, self._sigchldhandler) self._oldsigchldhandler = o self._socketunlinked = False def _unlinksocket(self): if not self._socketunlinked: self._servicehandler.unlinksocket(self.address) self._socketunlinked = True def _cleanup(self): signal.signal(signal.SIGCHLD, self._oldsigchldhandler) self._sock.close() self._unlinksocket() # don't kill child processes as they have active clients, just wait self._reapworkers(0) def run(self): try: self._mainloop() finally: self._cleanup() def _mainloop(self): exiting = False h = self._servicehandler selector = selectors.DefaultSelector() selector.register(self._sock, selectors.EVENT_READ) while True: if not exiting and h.shouldexit(): # clients can no longer connect() to the domain socket, so # we stop queuing new requests. # for requests that are queued (connect()-ed, but haven't been # accept()-ed), handle them before exit. otherwise, clients # waiting for recv() will receive ECONNRESET. self._unlinksocket() exiting = True ready = selector.select(timeout=h.pollinterval) if not ready: # only exit if we completed all queued requests if exiting: break continue try: conn, _addr = self._sock.accept() except socket.error as inst: if inst.args[0] == errno.EINTR: continue raise pid = os.fork() if pid: try: self.ui.debug('forked worker process (pid=%d)\n' % pid) self._workerpids.add(pid) h.newconnection() finally: conn.close() # release handle in parent process else: try: selector.close() self._sock.close() self._runworker(conn) conn.close() os._exit(0) except: # never return, hence no re-raises try: self.ui.traceback(force=True) finally: os._exit(255) selector.close() def _sigchldhandler(self, signal, frame): self._reapworkers(os.WNOHANG) def _reapworkers(self, options): while self._workerpids: try: pid, _status = os.waitpid(-1, options) except OSError as inst: if inst.errno == errno.EINTR: continue if inst.errno != errno.ECHILD: raise # no child processes at all (reaped by other waitpid()?) self._workerpids.clear() return if pid == 0: # no waitable child processes return self.ui.debug('worker process exited (pid=%d)\n' % pid) self._workerpids.discard(pid) def _runworker(self, conn): signal.signal(signal.SIGCHLD, self._oldsigchldhandler) _initworkerprocess() h = self._servicehandler try: _serverequest(self.ui, self.repo, conn, h.createcmdserver) finally: gc.collect() # trigger __del__ since worker process uses os._exit