view mercurial/commandserver.py @ 30779:38aa1ca97b6a

repair: migrate revlogs during upgrade

Our next step for in-place upgrade is to migrate store data. Revlogs
are the biggest source of data within the store and a store is useless
without them, so we implement their migration first.

Our strategy for migrating revlogs is to walk the store and call
`revlog.clone()` on each revlog. There are some minor complications.

Because revlogs have different storage options (e.g. changelog has
generaldelta and delta chains disabled), we need to obtain the
correct class of revlog so inserted data is encoded properly for its
type.

Various attempts at implementing progress indicators that didn't lead
to frustration from false "it's almost done" indicators were made.

I initially used a single progress bar based on number of revlogs.
However, this quickly churned through all filelogs, got to 99% then
effectively froze at 99.99% when it got to the manifest.

So I converted the progress bar to total revision count. This was a
little bit better. But the manifest was still significantly slower
than filelogs and it took forever to process the last few percent.

I then tried both revision/chunk bytes and raw bytes as the
denominator. This had the opposite effect: because so much data is in
manifests, it would churn through filelogs without showing much
progress. When it got to manifests, it would fill in 90+% of the
progress bar.

I finally gave up having a unified progress bar and instead implemented
3 progress bars: 1 for filelog revisions, 1 for manifest revisions, and
1 for changelog revisions. I added extra messages indicating the total
number of revisions of each so users know there are more progress bars
coming.

I also added extra messages before and after each stage to give extra
details about what is happening. Strictly speaking, this isn't
necessary. But the numbers are impressive. For example, when converting
a non-generaldelta mozilla-central repository, the messages you see are:

   migrating 2475593 total revisions (1833043 in filelogs, 321156 in manifests, 321394 in changelog)
   migrating 1.67 GB in store; 2508 GB tracked data
   migrating 267868 filelogs containing 1833043 revisions (1.09 GB in store; 57.3 GB tracked data)
   finished migrating 1833043 filelog revisions across 267868 filelogs; change in size: -415776 bytes
   migrating 1 manifests containing 321156 revisions (518 MB in store; 2451 GB tracked data)

That "2508 GB" figure really blew me away. I had no clue that the raw
tracked data in mozilla-central was that large. Granted, 2451 GB is in
the manifest and "only" 57.3 GB is in filelogs. But still.

It's worth noting that gratuitous loading of source revlogs in order
to display numbers and progress bars does serve a purpose: it ensures
we can open all source revlogs. We don't want to spend several minutes
copying revlogs only to encounter a permissions error or similar later.

As part of this commit, we also add swapping of the store directory
to the upgrade function. After revlogs are converted, we move the
old store into the backup directory then move the temporary repo's
store into the old store's location. On well-behaved systems, this
should be 2 atomic operations and the window of inconsistency show be
very narrow.

There are still a few improvements to be made to store copying and
upgrading. But this commit gets the bulk of the work out of the way.

# commandserver.py - communicate with Mercurial's API over a pipe
#
#  Copyright 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 errno
import gc
import os
import random
import select
import signal
import socket
import struct
import traceback

from .i18n import _
from . import (
    encoding,
    error,
    pycompat,
    util,
)

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", None)
        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"""
        pass

    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)

        ret = (dispatch.dispatch(req) or 0) & 255 # might return None

        # restore old cwd
        if '--cwd' in args:
            os.chdir(self.cwd)

        self.cresult.write(struct.pack('>i', int(ret)))

    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' % util.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

def _protectio(ui):
    """ duplicates streams and redirect original to null if ui uses stdio """
    ui.flush()
    newfiles = []
    nullfd = os.open(os.devnull, os.O_RDWR)
    for f, sysf, mode in [(ui.fin, util.stdin, 'rb'),
                          (ui.fout, util.stdout, 'wb')]:
        if f is sysf:
            newfd = os.dup(f.fileno())
            os.dup2(nullfd, f.fileno())
            f = os.fdopen(newfd, mode)
        newfiles.append(f)
    os.close(nullfd)
    return tuple(newfiles)

def _restoreio(ui, fin, fout):
    """ restores streams from duplicated ones """
    ui.flush()
    for f, uif in [(fin, ui.fin), (fout, ui.fout)]:
        if f is not uif:
            os.dup2(f.fileno(), uif.fileno())
            f.close()

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.
        fin, fout = _protectio(ui)
        try:
            sv = server(ui, self.repo, fin, fout)
            return sv.serve()
        finally:
            sv.cleanup()
            _restoreio(ui, fin, fout)

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.warn(_('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)

    def unlinksocket(self, address):
        os.unlink(address)

    def printbanner(self, address):
        self.ui.status(_('listening at %s\n') % address)
        self.ui.flush()  # avoid buffering of status message

    def shouldexit(self):
        """True if server should shut down; checked per pollinterval"""
        return False

    def newconnection(self):
        """Called when main process notices new connection"""
        pass

    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

    def init(self):
        self._sock = socket.socket(socket.AF_UNIX)
        self._servicehandler.bindsocket(self._sock, self.address)
        self._sock.listen(socket.SOMAXCONN)
        o = signal.signal(signal.SIGCHLD, self._sigchldhandler)
        self._oldsigchldhandler = o
        self._servicehandler.printbanner(self.address)

    def _cleanup(self):
        signal.signal(signal.SIGCHLD, self._oldsigchldhandler)
        self._sock.close()
        self._servicehandler.unlinksocket(self.address)
        # 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):
        h = self._servicehandler
        while not h.shouldexit():
            try:
                ready = select.select([self._sock], [], [], h.pollinterval)[0]
                if not ready:
                    continue
                conn, _addr = self._sock.accept()
            except (select.error, 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:
                    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)

    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