hgext/fastannotate/support.py

rust-status: cap the number of concurrent threads to 16

During benchmarking it was determined that the use of more threads is very
advantageous... until we use more than 16. This is most likely due to some
resource contention (thrashing, etc.). Until we have time to figure out and
fix the underlying cause, let's just cap at 16 threads.

Differential Revision: https://phab.mercurial-scm.org/D12384

# Copyright 2016-present Facebook. All Rights Reserved.
#
# support: fastannotate support for hgweb, and filectx
#
# 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 mercurial.pycompat import getattr
from mercurial import (
    context as hgcontext,
    dagop,
    extensions,
    hgweb,
    patch,
    util,
)

from . import (
    context,
    revmap,
)


class _lazyfctx(object):
    """delegates to fctx but do not construct fctx when unnecessary"""

    def __init__(self, repo, node, path):
        self._node = node
        self._path = path
        self._repo = repo

    def node(self):
        return self._node

    def path(self):
        return self._path

    @util.propertycache
    def _fctx(self):
        return context.resolvefctx(self._repo, self._node, self._path)

    def __getattr__(self, name):
        return getattr(self._fctx, name)


def _convertoutputs(repo, annotated, contents):
    """convert fastannotate outputs to vanilla annotate format"""
    # fastannotate returns: [(nodeid, linenum, path)], [linecontent]
    # convert to what fctx.annotate returns: [annotateline]
    results = []
    fctxmap = {}
    annotateline = dagop.annotateline
    for i, (hsh, linenum, path) in enumerate(annotated):
        if (hsh, path) not in fctxmap:
            fctxmap[(hsh, path)] = _lazyfctx(repo, hsh, path)
        # linenum: the user wants 1-based, we have 0-based.
        lineno = linenum + 1
        fctx = fctxmap[(hsh, path)]
        line = contents[i]
        results.append(annotateline(fctx=fctx, lineno=lineno, text=line))
    return results


def _getmaster(fctx):
    """(fctx) -> str"""
    return fctx._repo.ui.config(b'fastannotate', b'mainbranch') or b'default'


def _doannotate(fctx, follow=True, diffopts=None):
    """like the vanilla fctx.annotate, but do it via fastannotate, and make
    the output format compatible with the vanilla fctx.annotate.
    may raise Exception, and always return line numbers.
    """
    master = _getmaster(fctx)

    with context.fctxannotatecontext(fctx, follow, diffopts) as ac:
        try:
            annotated, contents = ac.annotate(
                fctx.rev(), master=master, showpath=True, showlines=True
            )
        except Exception:
            ac.rebuild()  # try rebuild once
            fctx._repo.ui.debug(
                b'fastannotate: %s: rebuilding broken cache\n' % fctx._path
            )
            try:
                annotated, contents = ac.annotate(
                    fctx.rev(), master=master, showpath=True, showlines=True
                )
            except Exception:
                raise

    assert annotated and contents
    return _convertoutputs(fctx._repo, annotated, contents)


def _hgwebannotate(orig, fctx, ui):
    diffopts = patch.difffeatureopts(
        ui, untrusted=True, section=b'annotate', whitespace=True
    )
    return _doannotate(fctx, diffopts=diffopts)


def _fctxannotate(
    orig, self, follow=False, linenumber=False, skiprevs=None, diffopts=None
):
    if skiprevs:
        # skiprevs is not supported yet
        return orig(
            self, follow, linenumber, skiprevs=skiprevs, diffopts=diffopts
        )
    try:
        return _doannotate(self, follow, diffopts)
    except Exception as ex:
        self._repo.ui.debug(
            b'fastannotate: falling back to the vanilla annotate: %r\n' % ex
        )
        return orig(self, follow=follow, skiprevs=skiprevs, diffopts=diffopts)


def _remotefctxannotate(orig, self, follow=False, skiprevs=None, diffopts=None):
    # skipset: a set-like used to test if a fctx needs to be downloaded
    with context.fctxannotatecontext(self, follow, diffopts) as ac:
        skipset = revmap.revmap(ac.revmappath)
    return orig(
        self, follow, skiprevs=skiprevs, diffopts=diffopts, prefetchskip=skipset
    )


def replacehgwebannotate():
    extensions.wrapfunction(hgweb.webutil, b'annotate', _hgwebannotate)


def replacefctxannotate():
    extensions.wrapfunction(hgcontext.basefilectx, b'annotate', _fctxannotate)