# HG changeset patch # User Gregory Szorc # Date 1444764639 25200 # Node ID c347d532bb566b5af961800850563d1f6d35ed86 # Parent 62b0fa0d87875333f03afd1bb07ebf4a7b5ca9d6 exchange: support sorting URLs by client-side preferences Not all bundles are appropriate for all clients. For example, someone with a slow Internet connection may want to prefer bz2 bundles over gzip bundles because they are smaller and don't take as long to transfer. This is information that a server cannot know on its own. So, we invent a mechanism for "preferring" server-advertised URLs based on their attributes. We could invent a negotiation between client and server where the client sends its preferences and the sorting/filtering is done server-side. However, this feels complex. We can avoid complicating the wire protocol and exposing ourselves to backwards compatible concerns by performing the sorting locally. This patch defines a new config option for expressing preferred attributes in server-advertised bundles. At Mozilla, we leverage this feature so clients in fast data centers prefer uncompressed bundles. (We advertise gzip bundles first because that is a reasonable default.) I consider this an advanced feature. I'm on the fence as to whether it should be documented in `hg help config`. diff -r 62b0fa0d8787 -r c347d532bb56 mercurial/exchange.py --- a/mercurial/exchange.py Tue Oct 13 12:31:19 2015 -0700 +++ b/mercurial/exchange.py Tue Oct 13 12:30:39 2015 -0700 @@ -1622,7 +1622,7 @@ 'operator)\n')) return - # TODO sort entries by user preferences. + entries = sortclonebundleentries(repo.ui, entries) url = entries[0]['URL'] repo.ui.status(_('applying clone bundle from %s\n') % url) @@ -1700,6 +1700,51 @@ return newentries +def sortclonebundleentries(ui, entries): + # experimental config: experimental.clonebundleprefers + prefers = ui.configlist('experimental', 'clonebundleprefers', default=[]) + if not prefers: + return list(entries) + + prefers = [p.split('=', 1) for p in prefers] + + # Our sort function. + def compareentry(a, b): + for prefkey, prefvalue in prefers: + avalue = a.get(prefkey) + bvalue = b.get(prefkey) + + # Special case for b missing attribute and a matches exactly. + if avalue is not None and bvalue is None and avalue == prefvalue: + return -1 + + # Special case for a missing attribute and b matches exactly. + if bvalue is not None and avalue is None and bvalue == prefvalue: + return 1 + + # We can't compare unless attribute present on both. + if avalue is None or bvalue is None: + continue + + # Same values should fall back to next attribute. + if avalue == bvalue: + continue + + # Exact matches come first. + if avalue == prefvalue: + return -1 + if bvalue == prefvalue: + return 1 + + # Fall back to next attribute. + continue + + # If we got here we couldn't sort by attributes and prefers. Fall + # back to index order. + return 0 + + return sorted(entries, cmp=compareentry) + def trypullbundlefromurl(ui, repo, url): """Attempt to apply a bundle from a URL.""" lock = repo.lock() diff -r 62b0fa0d8787 -r c347d532bb56 tests/test-clonebundles.t --- a/tests/test-clonebundles.t Tue Oct 13 12:31:19 2015 -0700 +++ b/tests/test-clonebundles.t Tue Oct 13 12:30:39 2015 -0700 @@ -261,3 +261,97 @@ searching for changes no changes found #endif + +Set up manifest for testing preferences +(Remember, the TYPE does not have to match reality - the URL is +important) + + $ cp full.hg gz-a.hg + $ cp full.hg gz-b.hg + $ cp full.hg bz2-a.hg + $ cp full.hg bz2-b.hg + $ cat > server/.hg/clonebundles.manifest << EOF + > http://localhost:$HGPORT1/gz-a.hg BUNDLESPEC=gzip-v2 extra=a + > http://localhost:$HGPORT1/bz2-a.hg BUNDLESPEC=bzip2-v2 extra=a + > http://localhost:$HGPORT1/gz-b.hg BUNDLESPEC=gzip-v2 extra=b + > http://localhost:$HGPORT1/bz2-b.hg BUNDLESPEC=bzip2-v2 extra=b + > EOF + +Preferring an undefined attribute will take first entry + + $ hg --config experimental.clonebundleprefers=foo=bar clone -U http://localhost:$HGPORT prefer-foo + applying clone bundle from http://localhost:$HGPORT1/gz-a.hg + adding changesets + adding manifests + adding file changes + added 2 changesets with 2 changes to 2 files + finished applying clone bundle + searching for changes + no changes found + +Preferring bz2 type will download first entry of that type + + $ hg --config experimental.clonebundleprefers=COMPRESSION=bzip2 clone -U http://localhost:$HGPORT prefer-bz + applying clone bundle from http://localhost:$HGPORT1/bz2-a.hg + adding changesets + adding manifests + adding file changes + added 2 changesets with 2 changes to 2 files + finished applying clone bundle + searching for changes + no changes found + +Preferring multiple values of an option works + + $ hg --config experimental.clonebundleprefers=COMPRESSION=unknown,COMPRESSION=bzip2 clone -U http://localhost:$HGPORT prefer-multiple-bz + applying clone bundle from http://localhost:$HGPORT1/bz2-a.hg + adding changesets + adding manifests + adding file changes + added 2 changesets with 2 changes to 2 files + finished applying clone bundle + searching for changes + no changes found + +Sorting multiple values should get us back to original first entry + + $ hg --config experimental.clonebundleprefers=BUNDLESPEC=unknown,BUNDLESPEC=gzip-v2,BUNDLESPEC=bzip2-v2 clone -U http://localhost:$HGPORT prefer-multiple-gz + applying clone bundle from http://localhost:$HGPORT1/gz-a.hg + adding changesets + adding manifests + adding file changes + added 2 changesets with 2 changes to 2 files + finished applying clone bundle + searching for changes + no changes found + +Preferring multiple attributes has correct order + + $ hg --config experimental.clonebundleprefers=extra=b,BUNDLESPEC=bzip2-v2 clone -U http://localhost:$HGPORT prefer-separate-attributes + applying clone bundle from http://localhost:$HGPORT1/bz2-b.hg + adding changesets + adding manifests + adding file changes + added 2 changesets with 2 changes to 2 files + finished applying clone bundle + searching for changes + no changes found + +Test where attribute is missing from some entries + + $ cat > server/.hg/clonebundles.manifest << EOF + > http://localhost:$HGPORT1/gz-a.hg BUNDLESPEC=gzip-v2 + > http://localhost:$HGPORT1/bz2-a.hg BUNDLESPEC=bzip2-v2 + > http://localhost:$HGPORT1/gz-b.hg BUNDLESPEC=gzip-v2 extra=b + > http://localhost:$HGPORT1/bz2-b.hg BUNDLESPEC=bzip2-v2 extra=b + > EOF + + $ hg --config experimental.clonebundleprefers=extra=b clone -U http://localhost:$HGPORT prefer-partially-defined-attribute + applying clone bundle from http://localhost:$HGPORT1/gz-b.hg + adding changesets + adding manifests + adding file changes + added 2 changesets with 2 changes to 2 files + finished applying clone bundle + searching for changes + no changes found