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Set accum of freshly added validator -(total voting power) (#2785)

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* set the accum of a new validator to (-total voting power):

- disincentivize validators to unbond, then rebon to reset their
negative Accum to zero

additional unrelated changes:
- do not capitalize error msgs
- fix typo

* review comments: (re)capitalize errors & delete obsolete comments

* More changes suggested by @melekes

* WIP: do not batch clip (#2809)

* substract avgAccum on each iteration

- temporarily skip test

* remove unused method safeMulClip / safeMul

* always substract the avg accum

 - temp. skip another test

* remove overflow / underflow tests & add tests for avgAccum:

- add test for computeAvgAccum
- as we substract the avgAccum now we will not trivially over/underflow

* address @cwgoes' comments

* shift by avg at the end of IncrementAccum

* Add comment to MaxTotalVotingPower

* Guard inputs to not exceed MaxTotalVotingPower

* Address review comments:

 - do not fetch current validator from set again
 - update error message

* Address a few review comments:

 - fix typo
 - extract variable

* address more review comments:

 - clarify 1.125*totalVotingPower == totalVotingPower + (totalVotingPower >> 3)

* review comments: panic instead of "clipping":

 - total voting power is guarded to not exceed MaxTotalVotingPower ->
 panic if this invariant is violated

* fix failing test
This commit is contained in:
Ismail Khoffi
2018-11-28 19:12:17 +01:00
committed by Ethan Buchman
parent b11788d36d
commit 3f987adc92
6 changed files with 144 additions and 111 deletions
Download Patch File Download Diff File Expand all files Collapse all files

40
state/execution.go
View File

@@ -356,20 +356,48 @@ func updateValidators(currentSet *types.ValidatorSet, updates []*types.Validator
address := valUpdate.Address
_, val := currentSet.GetByAddress(address)
// valUpdate.VotingPower is ensured to be non-negative in validation method
if valUpdate.VotingPower == 0 {
// remove val
if valUpdate.VotingPower == 0 { // remove val
_, removed := currentSet.Remove(address)
if !removed {
return fmt.Errorf("Failed to remove validator %X", address)
}
} else if val == nil {
// add val
} else if val == nil { // add val
// make sure we do not exceed MaxTotalVotingPower by adding this validator:
totalVotingPower := currentSet.TotalVotingPower()
updatedVotingPower := valUpdate.VotingPower + totalVotingPower
overflow := updatedVotingPower > types.MaxTotalVotingPower || updatedVotingPower < 0
if overflow {
return fmt.Errorf(
"Failed to add new validator %v. Adding it would exceed max allowed total voting power %v",
valUpdate,
types.MaxTotalVotingPower)
}
// TODO: issue #1558 update spec according to the following:
// Set Accum to -C*totalVotingPower (with C ~= 1.125) to make sure validators can't
// unbond/rebond to reset their (potentially previously negative) Accum to zero.
//
// Contract: totalVotingPower < MaxTotalVotingPower to ensure Accum does
// not exceed the bounds of int64.
//
// Compute Accum = -1.125*totalVotingPower == -(totalVotingPower + (totalVotingPower >> 3)).
valUpdate.Accum = -(totalVotingPower + (totalVotingPower >> 3))
added := currentSet.Add(valUpdate)
if !added {
return fmt.Errorf("Failed to add new validator %v", valUpdate)
}
} else {
// update val
} else { // update val
// make sure we do not exceed MaxTotalVotingPower by updating this validator:
totalVotingPower := currentSet.TotalVotingPower()
curVotingPower := val.VotingPower
updatedVotingPower := totalVotingPower - curVotingPower + valUpdate.VotingPower
overflow := updatedVotingPower > types.MaxTotalVotingPower || updatedVotingPower < 0
if overflow {
return fmt.Errorf(
"Failed to update existing validator %v. Updating it would exceed max allowed total voting power %v",
valUpdate,
types.MaxTotalVotingPower)
}
updated := currentSet.Update(valUpdate)
if !updated {
return fmt.Errorf("Failed to update validator %X to %v", address, valUpdate)