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Make snowman use snowflake directly instead of snowball #3403

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@yacovm yacovm commented Sep 19, 2024

Why this should be merged

Snowball was introduced in order to improve the stability of snowflake, by taking into account the history when returning the preference.

However, if deployed with a configuration where the preference is small enough, and a network partition causes a 50-50 split of the stake, it can actually backfire, as described in 6e1a905.

Additionally, latest research [1] points out that snowflake suffices for snowman.

[1] https://arxiv.org/abs/2404.14250

How this works

This commit removes snowball from snowman by substituting the snowball factory snowman uses, with a snowflake factory.

How this was tested

Added a test that simulates a mixed network which runs snowman with and without snowball, and ensures that a mixed network still converges.

Also ran a modified node on Fuji and monitored its consensus related metrics, and it seemed functioning well.

snow/consensus/snowball/binary_snowball_test.go Outdated Show resolved Hide resolved
snow/consensus/snowball/flat_test.go Outdated Show resolved Hide resolved
chains/manager.go Show resolved Hide resolved
snow/consensus/snowman/topological.go Show resolved Hide resolved
snow/consensus/snowman/mixed_test.go Show resolved Hide resolved
snow/consensus/snowball/tree_test.go Outdated Show resolved Hide resolved
snow/consensus/snowball/tree_test.go Outdated Show resolved Hide resolved
snow/consensus/snowball/tree_test.go Outdated Show resolved Hide resolved
@yacovm yacovm added the consensus This involves consensus label Sep 30, 2024
sb := newBinarySnowball(alphaPreference, terminationConditions, red)
require.Equal(red, sb.Preference())
require.False(sb.Finalized())
sf := newBinarySnowflake(alphaPreference, terminationConditions, red)
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Why is this test modified? It seems to be a duplicate of TestBinarySnowflake now.

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I'm not sure why this file is being modified. We aren't changing the code that it was previously testing... If we feel like the binarySnowflake struct needs additional coverage shouldn't we be adding new tests to the binary_snowflake_test.go file rather than here?

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ok will revert

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Because we aren't deleting the code that this was testing, nnary_snowball.go, why are we deleting the tests?

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Because we aren't deleting the code that this was testing, unary_snowball.go, why are we deleting the tests?

Comment on lines 36 to 45
var sm Consensus
if i%2 == 0 {
factory := TopologicalFactory{factory: snowball.SnowflakeFactory}
sm = factory.New()
} else {
factory := TopologicalFactory{factory: snowball.SnowballFactory}
sm = factory.New()
}

require.NoError(n.AddNode(t, sm))
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nit: Seems like we can cleanup the if block a bit

Suggested change
var sm Consensus
if i%2 == 0 {
factory := TopologicalFactory{factory: snowball.SnowflakeFactory}
sm = factory.New()
} else {
factory := TopologicalFactory{factory: snowball.SnowballFactory}
sm = factory.New()
}
require.NoError(n.AddNode(t, sm))
var sbFactory snowball.Factory
if i%2 == 0 {
sbFactory = snowball.SnowflakeFactory
} else {
sbFactory = snowball.SnowballFactory
}
factory := TopologicalFactory{factory: sbFactory}
sm := factory.New()
require.NoError(n.AddNode(t, sm))

Comment on lines 488 to 492
// *
// 1/ \
// R *
// / \
// G B
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What do the numbers on the edges mean? It seems like they are referencing Snowball counters but we are using snowflake here and not snowball.

@yacovm yacovm force-pushed the removeSnowball branch 3 times, most recently from 1c161b2 to be4ccba Compare October 21, 2024 15:13
Snowball was introduced in order to improve the stability of snowflake,
by taking into account the history when returning the preference.

However, if deployed with a configuration where the preference is small enough, and a network partition
causes a 50-50 split of the stake, it can actually backfire, as described in 6e1a905.

Additionally, latest research [1] points out that snowflake suffices for snowman.

This commit removes snowball from snowman and adds a test that simulates a mixed network
which runs snowman with and without snowball, and ensures that a mixed network still converges.

[1] https://arxiv.org/abs/2404.14250

Signed-off-by: Yacov Manevich <[email protected]>
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Code changes LGTM. Going to hold off on approving/merging until we've canaried this out on Fuji + Mainnet

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This PR has become stale because it has been open for 30 days with no activity. Adding the lifecycle/frozen label will cause this PR to ignore lifecycle events.

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3 participants