discovery: add new set-based discovery
Adds a new discovery method based on repeatedly sampling the still
undecided subset of the local node graph to determine the set of nodes
common to both the client and the server.
For small differences between client and server, it uses about the same
or slightly fewer roundtrips than the old tree-based discovery. For
larger differences, it typically reduces the number of roundtrips
drastically (from 150 to 4, for instance).
The old discovery code now lives in treediscovery.py, the new code is
in setdiscovery.py.
Still missing is a hook for extensions to contribute nodes to the
initial sample. For instance, Augie's remotebranches could contribute
the last known state of the server's heads.
Credits for the actual sampler and computing common heads instead of
bases go to Benoit Boissinot.
Function to test discovery between two repos in both directions, using both the local shortcut
(which is currently not activated by default) and the full remotable protocol:
$ testdesc() { # revs_a, revs_b, dagdesc
> if [ -e foo ]; then rm -rf foo; fi
> hg init foo
> cd foo
> hg debugbuilddag "$3"
> hg clone . a $1 --quiet
> hg clone . b $2 --quiet
> echo
> echo "% -- a -> b tree"
> hg -R a debugdiscovery b --verbose --old
> echo
> echo "% -- a -> b set"
> hg -R a debugdiscovery b --verbose --debug
> echo
> echo "% -- b -> a tree"
> hg -R b debugdiscovery a --verbose --old
> echo
> echo "% -- b -> a set"
> hg -R b debugdiscovery a --verbose --debug
> cd ..
> }
Small superset:
$ testdesc '-ra1 -ra2' '-rb1 -rb2 -rb3' '
> +2:f +1:a1:b1
> <f +4 :a2
> +5 :b2
> <f +3 :b3'
% -- a -> b tree
comparing with b
searching for changes
unpruned common: b5714e113bc0 66f7d451a68b 01241442b3c2
common heads: b5714e113bc0 01241442b3c2
local is subset
% -- a -> b set
comparing with b
query 1; heads
searching for changes
taking initial sample
searching: 2 queries
query 2; still undecided: 4, sample size is: 4
2 total queries
common heads: b5714e113bc0 01241442b3c2
local is subset
% -- b -> a tree
comparing with a
searching for changes
unpruned common: b5714e113bc0 01241442b3c2
common heads: b5714e113bc0 01241442b3c2
remote is subset
% -- b -> a set
comparing with a
query 1; heads
searching for changes
all remote heads known locally
common heads: b5714e113bc0 01241442b3c2
remote is subset
Many new:
$ testdesc '-ra1 -ra2' '-rb' '
> +2:f +3:a1 +3:b
> <f +30 :a2'
% -- a -> b tree
comparing with b
searching for changes
unpruned common: bebd167eb94d
common heads: bebd167eb94d
% -- a -> b set
comparing with b
query 1; heads
searching for changes
taking quick initial sample
searching: 2 queries
query 2; still undecided: 35, sample size is: 35
2 total queries
common heads: bebd167eb94d
% -- b -> a tree
comparing with a
searching for changes
unpruned common: bebd167eb94d 66f7d451a68b
common heads: bebd167eb94d
% -- b -> a set
comparing with a
query 1; heads
searching for changes
taking initial sample
searching: 2 queries
query 2; still undecided: 3, sample size is: 3
2 total queries
common heads: bebd167eb94d
Both sides many new with stub:
$ testdesc '-ra1 -ra2' '-rb' '
> +2:f +2:a1 +30 :b
> <f +30 :a2'
% -- a -> b tree
comparing with b
searching for changes
unpruned common: 2dc09a01254d
common heads: 2dc09a01254d
% -- a -> b set
comparing with b
query 1; heads
searching for changes
taking quick initial sample
searching: 2 queries
query 2; still undecided: 34, sample size is: 34
2 total queries
common heads: 2dc09a01254d
% -- b -> a tree
comparing with a
searching for changes
unpruned common: 66f7d451a68b 2dc09a01254d
common heads: 2dc09a01254d
% -- b -> a set
comparing with a
query 1; heads
searching for changes
taking initial sample
searching: 2 queries
query 2; still undecided: 30, sample size is: 30
2 total queries
common heads: 2dc09a01254d
Both many new:
$ testdesc '-ra' '-rb' '
> +2:f +30 :b
> <f +30 :a'
% -- a -> b tree
comparing with b
searching for changes
unpruned common: 66f7d451a68b
common heads: 66f7d451a68b
% -- a -> b set
comparing with b
query 1; heads
searching for changes
taking quick initial sample
searching: 2 queries
query 2; still undecided: 32, sample size is: 32
2 total queries
common heads: 66f7d451a68b
% -- b -> a tree
comparing with a
searching for changes
unpruned common: 66f7d451a68b
common heads: 66f7d451a68b
% -- b -> a set
comparing with a
query 1; heads
searching for changes
taking quick initial sample
searching: 2 queries
query 2; still undecided: 32, sample size is: 32
2 total queries
common heads: 66f7d451a68b
Both many new skewed:
$ testdesc '-ra' '-rb' '
> +2:f +30 :b
> <f +50 :a'
% -- a -> b tree
comparing with b
searching for changes
unpruned common: 66f7d451a68b
common heads: 66f7d451a68b
% -- a -> b set
comparing with b
query 1; heads
searching for changes
taking quick initial sample
searching: 2 queries
query 2; still undecided: 52, sample size is: 52
2 total queries
common heads: 66f7d451a68b
% -- b -> a tree
comparing with a
searching for changes
unpruned common: 66f7d451a68b
common heads: 66f7d451a68b
% -- b -> a set
comparing with a
query 1; heads
searching for changes
taking quick initial sample
searching: 2 queries
query 2; still undecided: 32, sample size is: 32
2 total queries
common heads: 66f7d451a68b
Both many new on top of long history:
$ testdesc '-ra' '-rb' '
> +1000:f +30 :b
> <f +50 :a'
% -- a -> b tree
comparing with b
searching for changes
unpruned common: 7ead0cba2838
common heads: 7ead0cba2838
% -- a -> b set
comparing with b
query 1; heads
searching for changes
taking quick initial sample
searching: 2 queries
query 2; still undecided: 1050, sample size is: 11
sampling from both directions
searching: 3 queries
query 3; still undecided: 31, sample size is: 31
3 total queries
common heads: 7ead0cba2838
% -- b -> a tree
comparing with a
searching for changes
unpruned common: 7ead0cba2838
common heads: 7ead0cba2838
% -- b -> a set
comparing with a
query 1; heads
searching for changes
taking quick initial sample
searching: 2 queries
query 2; still undecided: 1030, sample size is: 11
sampling from both directions
searching: 3 queries
query 3; still undecided: 16, sample size is: 16
3 total queries
common heads: 7ead0cba2838