htlcswitch/link: correct bias in fee update backoff #1482
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
cfromknecht
force-pushed
the
uniform-fee-update-timeout
branch
from
472d8d3
to
0bc37f7
Compare
This commit corrects the distribution used to schedule a link's randomized backoff for fee updates. Currently, our algorithm biases the lowest value in the range, with probability equal to lower/upper, or the ratio of the lower bound to the upper. This distribution is skewed more heavily as lower approaches upper. The solution is to sample a random value in the range upper-lower, then add this to our lower bound. The effect is a uniformly distributed timeout in [lower, upper).
cfromknecht
force-pushed
the
uniform-fee-update-timeout
branch
from
0bc37f7
to
5fa8124
Compare
cfromknecht
force-pushed
the
uniform-fee-update-timeout
branch
from
f9be9f3
to
12f74f7
Compare
Roasbeef
reviewed
Jul 4, 2018
| @@ -1497,7 +1497,7 @@ func newSingleLinkTestHarness(chanAmt, chanReserve btcutil.Amount) ( | |||
| // to not trigger commit updates automatically during tests. | |||
| BatchSize: 10000, | |||
| MinFeeUpdateTimeout: 30 * time.Minute, | |||
| MaxFeeUpdateTimeout: 30 * time.Minute, | |||
| MaxFeeUpdateTimeout: 40 * time.Minute, | |||
There was a problem hiding this comment.
Why is 40 more realistic than 30?
There was a problem hiding this comment.
Since we now do upper-lower, this would panic because we're passing in 0 to math.Rand.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This commit corrects the distribution used to
schedule a link's randomized backoff for fee
updates. Currently, our algorithm biases the
lowest value in the range, with probability
equal to lower/upper, or the ratio of the lower
bound to the upper. This distribution is skewed
more heavily as lower approaches upper.
The solution is to sample a random value in the
range upper-lower, then add this to our lower
bound. The effect is a uniformly distributed
timeout in [lower, upper).
Just realizing that I noted this in a pending review of #1229, but forgot to publish before PR was merged.