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config.go
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config.go
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package coordinate
// Config is used to set the parameters of the Vivaldi-based coordinate mapping
// algorithm.
//
// The following references are called out at various points in the documentation
// here:
//
// [1] Dabek, Frank, et al. "Vivaldi: A decentralized network coordinate system."
// ACM SIGCOMM Computer Communication Review. Vol. 34. No. 4. ACM, 2004.
// [2] Ledlie, Jonathan, Paul Gardner, and Margo I. Seltzer. "Network Coordinates
// in the Wild." NSDI. Vol. 7. 2007.
// [3] Lee, Sanghwan, et al. "On suitability of Euclidean embedding for
// host-based network coordinate systems." Networking, IEEE/ACM Transactions
// on 18.1 (2010): 27-40.
type Config struct {
// The dimensionality of the coordinate system. As discussed in [2], more
// dimensions improves the accuracy of the estimates up to a point. Per [2]
// we chose 8 dimensions plus a non-Euclidean height.
Dimensionality uint
// VivaldiErrorMax is the default error value when a node hasn't yet made
// any observations. It also serves as an upper limit on the error value in
// case observations cause the error value to increase without bound.
VivaldiErrorMax float64
// VivaldiCE is a tuning factor that controls the maximum impact an
// observation can have on a node's confidence. See [1] for more details.
VivaldiCE float64
// VivaldiCC is a tuning factor that controls the maximum impact an
// observation can have on a node's coordinate. See [1] for more details.
VivaldiCC float64
// AdjustmentWindowSize is a tuning factor that determines how many samples
// we retain to calculate the adjustment factor as discussed in [3]. Setting
// this to zero disables this feature.
AdjustmentWindowSize uint
// HeightMin is the minimum value of the height parameter. Since this
// always must be positive, it will introduce a small amount error, so
// the chosen value should be relatively small compared to "normal"
// coordinates.
HeightMin float64
// LatencyFilterSamples is the maximum number of samples that are retained
// per node, in order to compute a median. The intent is to ride out blips
// but still keep the delay low, since our time to probe any given node is
// pretty infrequent. See [2] for more details.
LatencyFilterSize uint
// GravityRho is a tuning factor that sets how much gravity has an effect
// to try to re-center coordinates. See [2] for more details.
GravityRho float64
}
// DefaultConfig returns a Config that has some default values suitable for
// basic testing of the algorithm, but not tuned to any particular type of cluster.
func DefaultConfig() *Config {
return &Config{
Dimensionality: 8,
VivaldiErrorMax: 1.5,
VivaldiCE: 0.25,
VivaldiCC: 0.25,
AdjustmentWindowSize: 20,
HeightMin: 10.0e-6,
LatencyFilterSize: 3,
GravityRho: 150.0,
}
}