Mercurial > hg
view mercurial/logexchange.py @ 37631:2f626233859b
wireproto: implement batching on peer executor interface
This is a bit more complicated than non-batch requests because we
need to buffer sends until the last request arrives *and* we need
to support resolving futures as data arrives from the remote.
In a classical concurrent.futures executor model, the future
"starts" as soon as it is submitted. However, we have nothing to
start until the last command is submitted.
If we did nothing, calling result() would deadlock, since the future
hasn't "started." So in the case where we queue the command, we return
a special future type whose result() will trigger sendcommands().
This eliminates the deadlock potential. It also serves as a check
against callers who may be calling result() prematurely, as it will
prevent any subsequent callcommands() from working. This behavior
is slightly annoying and a bit restrictive. But it's the world
that half duplex connections forces on us.
In order to support streaming responses, we were previously using
a generator. But with a futures-based API, we're using futures
and not generators. So in order to get streaming, we need a
background thread to read data from the server.
The approach taken in this patch is to leverage the ThreadPoolExecutor
from concurrent.futures for managing a background thread. We create
an executor and future that resolves when all response data is
processed (or an error occurs). When exiting the context manager,
we wait on that background reading before returning.
I was hoping we could manually spin up a threading.Thread and this
would be simple. But I ran into a few deadlocks when implementing.
After looking at the source code to concurrent.futures, I figured
it would just be easier to use a ThreadPoolExecutor than implement
all the code needed to manually manage a thread.
To prove this works, a use of the batch API in discovery has been
updated.
Differential Revision: https://phab.mercurial-scm.org/D3269
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Fri, 13 Apr 2018 11:02:34 -0700 |
parents | 1ccd75027abb |
children | 0e50dda7e9c1 |
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# logexchange.py # # Copyright 2017 Augie Fackler <raf@durin42.com> # Copyright 2017 Sean Farley <sean@farley.io> # # 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 from .node import hex from . import ( util, vfs as vfsmod, ) # directory name in .hg/ in which remotenames files will be present remotenamedir = 'logexchange' def readremotenamefile(repo, filename): """ reads a file from .hg/logexchange/ directory and yields it's content filename: the file to be read yield a tuple (node, remotepath, name) """ vfs = vfsmod.vfs(repo.vfs.join(remotenamedir)) if not vfs.exists(filename): return f = vfs(filename) lineno = 0 for line in f: line = line.strip() if not line: continue # contains the version number if lineno == 0: lineno += 1 try: node, remote, rname = line.split('\0') yield node, remote, rname except ValueError: pass f.close() def readremotenames(repo): """ read the details about the remotenames stored in .hg/logexchange/ and yields a tuple (node, remotepath, name). It does not yields information about whether an entry yielded is branch or bookmark. To get that information, call the respective functions. """ for bmentry in readremotenamefile(repo, 'bookmarks'): yield bmentry for branchentry in readremotenamefile(repo, 'branches'): yield branchentry def writeremotenamefile(repo, remotepath, names, nametype): vfs = vfsmod.vfs(repo.vfs.join(remotenamedir)) f = vfs(nametype, 'w', atomictemp=True) # write the storage version info on top of file # version '0' represents the very initial version of the storage format f.write('0\n\n') olddata = set(readremotenamefile(repo, nametype)) # re-save the data from a different remote than this one. for node, oldpath, rname in sorted(olddata): if oldpath != remotepath: f.write('%s\0%s\0%s\n' % (node, oldpath, rname)) for name, node in sorted(names.iteritems()): if nametype == "branches": for n in node: f.write('%s\0%s\0%s\n' % (n, remotepath, name)) elif nametype == "bookmarks": if node: f.write('%s\0%s\0%s\n' % (node, remotepath, name)) f.close() def saveremotenames(repo, remotepath, branches=None, bookmarks=None): """ save remotenames i.e. remotebookmarks and remotebranches in their respective files under ".hg/logexchange/" directory. """ wlock = repo.wlock() try: if bookmarks: writeremotenamefile(repo, remotepath, bookmarks, 'bookmarks') if branches: writeremotenamefile(repo, remotepath, branches, 'branches') finally: wlock.release() def activepath(repo, remote): """returns remote path""" local = None # is the remote a local peer local = remote.local() # determine the remote path from the repo, if possible; else just # use the string given to us rpath = remote if local: rpath = remote._repo.root elif not isinstance(remote, bytes): rpath = remote._url # represent the remotepath with user defined path name if exists for path, url in repo.ui.configitems('paths'): # remove auth info from user defined url url = util.removeauth(url) if url == rpath: rpath = path break return rpath def pullremotenames(localrepo, remoterepo): """ pulls bookmarks and branches information of the remote repo during a pull or clone operation. localrepo is our local repository remoterepo is the peer instance """ remotepath = activepath(localrepo, remoterepo) bookmarks = remoterepo.listkeys('bookmarks') # on a push, we don't want to keep obsolete heads since # they won't show up as heads on the next pull, so we # remove them here otherwise we would require the user # to issue a pull to refresh the storage bmap = {} repo = localrepo.unfiltered() for branch, nodes in remoterepo.branchmap().iteritems(): bmap[branch] = [] for node in nodes: if node in repo and not repo[node].obsolete(): bmap[branch].append(hex(node)) saveremotenames(localrepo, remotepath, bmap, bookmarks)