nodemap: introduce append-only incremental update of the persistent data
Rewriting the full nodemap for each transaction has a cost we would like to
avoid. We introduce a new way to write persistent nodemap data by adding new
information at the end for file. Any new and updated block as added at the end
of the file. The last block is the new root node.
With this method, some of the block already on disk get "dereferenced" and
become dead data. In later changesets, We'll start tracking the amount of dead
data to eventually re-generate a full nodemap.
Differential Revision: https://phab.mercurial-scm.org/D7886
#require serve
$ hg init server
$ hg serve -R server -p $HGPORT -d --pid-file=hg1.pid -E ../error.log
$ cat hg1.pid >> $DAEMON_PIDS
Check basic fetching
$ hg debugdownload "http://localhost:$HGPORT/?cmd=lookup&key=tip"
1 0000000000000000000000000000000000000000
$ hg debugdownload -o null.txt "http://localhost:$HGPORT/?cmd=lookup&key=null"
$ cat null.txt
1 0000000000000000000000000000000000000000
Check the request is made from the usual Mercurial logic
(rev details, give different content if the request has a Mercurial user agent)
$ get-with-headers.py --headeronly "localhost:$HGPORT" "rev/tip" content-type
200 Script output follows
content-type: text/html; charset=ascii
$ hg debugdownload "http://localhost:$HGPORT/rev/tip"
# HG changeset patch
# User
# Date 0 0
# Node ID 0000000000000000000000000000000000000000
Check other kind of compatible url
$ hg debugdownload ./null.txt
1 0000000000000000000000000000000000000000
Test largefile URL
------------------
$ cat << EOF >> $HGRCPATH
> [extensions]
> largefiles=
> EOF
$ killdaemons.py
$ rm -f error.log hg1.pid
$ hg serve -R server -p $HGPORT -d --pid-file=hg1.pid -E error.log
$ cat hg1.pid >> $DAEMON_PIDS
$ hg -R server debuglfput null.txt
a57b57b39ee4dc3da1e03526596007f480ecdbe8
$ hg --traceback debugdownload "largefile://a57b57b39ee4dc3da1e03526596007f480ecdbe8" --config paths.default=http://localhost:$HGPORT/
1 0000000000000000000000000000000000000000
from within a repository
$ hg clone http://localhost:$HGPORT/ client
no changes found
updating to branch default
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd client
$ hg path
default = http://localhost:$HGPORT/
$ hg debugdownload "largefile://a57b57b39ee4dc3da1e03526596007f480ecdbe8"
1 0000000000000000000000000000000000000000
$ cd ..