It's unreasonable to use time.Now() in distributed systems #19
Description
Describe The Bug
It's unreasonable to use time.Now() in distributed systems. Now if the these nodes would have slightly different system clocks, we could easily end up with different function called like below. As a result, the state of each node may be inconsistent, and then Consensus failure? (I don't know)
Code Snippets
// x/distribution/keeper/keeper.go L#213
func (k Keeper) CanDistribution(ctx sdk.Context) (bool, time.Time) {
if k.startNotDistriTimePoint.Nanosecond() <= 0 {
return true, k.startNotDistriTimePoint
}
nt := time.Now()
tEnd := k.startNotDistriTimePoint.Add(24 * 3600 * 1e9)
if nt.Before(tEnd) && nt.After(k.startNotDistriTimePoint) {
return false, k.startNotDistriTimePoint
} else {
k.SetStartNotDistributionTimePoint(ctx, time.Time{})
ctx.Logger().Info("time CanDistribution",
"time", k.startNotDistriTimePoint.Nanosecond())
}
return true, k.startNotDistriTimePoint
}// x/distribution/abci.go L#26
func BeginBlocker(ctx sdk.Context, req abci.RequestBeginBlock, k keeper.Keeper) {
...
k.GetStartNotDistributionTimePoint(ctx)
f, _ := k.CanDistribution(ctx)
if ctx.BlockHeight() > 1 && f {
previousProposer := k.GetPreviousProposerConsAddr(ctx)
k.AllocateTokens(ctx, sumPreviousPrecommitPower, previousTotalPower, previousProposer, req.LastCommitInfo.GetVotes())
}
...
}Input/Output
None
To Reproduce
To reproduce the above situation requires very strict conditions, like multi-full-nodes, slightly different system clocks, and more than 1/3 of voters veto proposal. So I just based on code analysis and guessing that the above situation may be happened.
Expected Behavior
Every non-faulty machine sees the same transaction log and computes the same state.
Desktop
- OS: [macOS Mojave 10.14.6]
**Additional Context **
It is more reasonable choice for you to call another function ctx.BlockHeader().Time, because of this variable is produced by Tendermint, rather than rlying on single node.
should be fixed like this nt := ctx.BlockHeader().Time
Contact Information
Email - zhouhaw@gmail.com