view hgext/clonebundles.py @ 26638:7afaf2566e25

revset: add optional offset argument to limit() predicate

It's common for GUI or web frontend to fetch chunk of revisions per batch
size. Previously it was possible only if revisions were sorted by revision
number.

  $ hg log -r 'limit({revspec} & :{last_known}, 101)'

So this patch introduces a general way to retrieve chunk of revisions after
skipping offset revisions.

  $ hg log -r 'limit({revspec}, 100, {last_count})'

This is a dumb implementation. We can optimize it for baseset and spanset
later.

# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

"""server side extension to advertise pre-generated bundles to seed clones.

The extension essentially serves the content of a .hg/clonebundles.manifest
file to clients that request it.

The clonebundles.manifest file contains a list of URLs and attributes. URLs
hold pre-generated bundles that a client fetches and applies. After applying
the pre-generated bundle, the client will connect back to the original server
and pull data not in the pre-generated bundle.

Manifest File Format:

The manifest file contains a newline (\n) delimited list of entries.

Each line in this file defines an available bundle. Lines have the format:

    <URL> [<key>=<value]

That is, a URL followed by extra metadata describing it. Metadata keys and
values should be URL encoded.

This metadata is optional. It is up to server operators to populate this
metadata.

Keys in UPPERCASE are reserved for use by Mercurial. All non-uppercase keys
can be used by site installations.

The server operator is responsible for generating the bundle manifest file.

Metadata Attributes:

TBD
"""

from mercurial import (
    extensions,
    wireproto,
)

testedwith = 'internal'

def capabilities(orig, repo, proto):
    caps = orig(repo, proto)

    # Only advertise if a manifest exists. This does add some I/O to requests.
    # But this should be cheaper than a wasted network round trip due to
    # missing file.
    if repo.opener.exists('clonebundles.manifest'):
        caps.append('clonebundles')

    return caps

@wireproto.wireprotocommand('clonebundles', '')
def bundles(repo, proto):
    """Server command for returning info for available bundles to seed clones.

    Clients will parse this response and determine what bundle to fetch.

    Other extensions may wrap this command to filter or dynamically emit
    data depending on the request. e.g. you could advertise URLs for
    the closest data center given the client's IP address.
    """
    return repo.opener.tryread('clonebundles.manifest')

def extsetup(ui):
    extensions.wrapfunction(wireproto, '_capabilities', capabilities)