- Fix failure to generate all possible combinations (backport #3132)

[denyeart]

• • Fix failure to generate all possible combinations

Bug happens when the endorsement policy is set to k-out-of-n where (n - k) > 1.
For example, when there are 6 organizations and the endorsement policy is set
to majority (i.e. 4-out-of-6). The combinations calculated by chooseKoutOfN()
in original code are as below.
[0 1 2 5], [0 1 2 5], [0 1 2 5], [0 1 3 5],
[0 1 3 5], [0 1 4 5], [0 2 3 5], [0 2 3 5],
[0 2 4 5], [0 3 4 5], [1 2 3 5], [1 2 3 5],
[1 2 4 5], [1 3 4 5], [2 3 4 5]

Obviously, the function fails to find out all the possible combinations. Some of
the combinations are overrided by child's call. This bug would trigger below
error sometimes when the alive peers are not within the above combinations.

[discovery] chaincodeQuery -> ERRO 13a Failed constructing descriptor for
chaincode chaincodes:<name:"XXXX" > ,: no peer combination can satisfy the
endorsement policy

To fix it, the last line of choose() should be changed to pass a copy of
"currentSubGroup" to the recursive call instead, i.e.

choose(n, targetAmount, i+1, append(make([]int, 0), currentSubGroup...), subGroups)

After applying the fix, the resulting combinations generated should be corrected
as below.
[0 1 2 3], [0 1 2 4], [0 1 2 5], [0 1 3 4],
[0 1 3 5], [0 1 4 5], [0 2 3 4], [0 2 3 5],
[0 2 4 5], [0 3 4 5], [1 2 3 4], [1 2 3 5],
[1 2 4 5], [1 3 4 5], [2 3 4 5]

Signed-off-by: Tim [email protected]

• • Fix failure to generate all possible combinations

Bug happens when the endorsement policy is set to k-out-of-n where (n - k) > 1.
For example, when there are 6 organizations and the endorsement policy is set
to majority (i.e. 4-out-of-6). The combinations calculated by chooseKoutOfN()
in original code are as below.
[0 1 2 5], [0 1 2 5], [0 1 2 5], [0 1 3 5],
[0 1 3 5], [0 1 4 5], [0 2 3 5], [0 2 3 5],
[0 2 4 5], [0 3 4 5], [1 2 3 5], [1 2 3 5],
[1 2 4 5], [1 3 4 5], [2 3 4 5]

Obviously, the function fails to find out all the possible combinations. Some of
the combinations are overrided by child's call. This bug would trigger below
error sometimes when the alive peers are not within the above combinations.

[discovery] chaincodeQuery -> ERRO 13a Failed constructing descriptor for
chaincode chaincodes:<name:"XXXX" > ,: no peer combination can satisfy the
endorsement policy

To fix it, the last line of choose() should be changed to pass a copy of
"currentSubGroup" to the recursive call instead, i.e.

choose(n, targetAmount, i+1, append(make([]int, 0), currentSubGroup...), subGroups)

After applying the fix, the resulting combinations generated should be corrected
as below.
[0 1 2 3], [0 1 2 4], [0 1 2 5], [0 1 3 4],
[0 1 3 5], [0 1 4 5], [0 2 3 4], [0 2 3 5],
[0 2 4 5], [0 3 4 5], [1 2 3 4], [1 2 3 5],
[1 2 4 5], [1 3 4 5], [2 3 4 5]

Signed-off-by: Tim [email protected]

• • Update choose_test.go

Signed-off-by: Tim [email protected]

• • Fix build error

Signed-off-by: Tim [email protected]
Signed-off-by: David Enyeart [email protected]