Replace the stats library usage in cluster_test.go with a small inline
distributionStats helper that computes mean, stddev, min, and max using
stdlib math.
The library was only used in a single test file and pulled in ~4k of
vendored code for trivial arithmetic.
Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>
The property test for the mRandomNodes function revealed that it may
sometimes pick out a sample of fewer than m nodes even when the number
of nodes to pick from (excluding the local node) is >= m. Rewrite it
using a random shuffle or permutation so that it always picks a
uniformly-distributed sample of the requested size whenever the
population is large enough.
Signed-off-by: Cory Snider <csnider@mirantis.com>
TestNetworkDBAlwaysConverges will occasionally find a failure where one
entry is missing on one node even after waiting a full five minutes. One
possible explanation is that the selection of nodes to gossip with is
biased in some way. Test that the mRandomNodes function picks a
uniformly distributed sample of node IDs of sufficient length.
The new test reveals that mRandomNodes may sometimes pick out a sample
of fewer than m nodes even when the number of nodes to pick from
(excluding the local node) is >= m. Put the test behind an xfail tag so
it is opt-in to run, without interfering with CI or bisecting.
Signed-off-by: Cory Snider <csnider@mirantis.com>
