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https://github.com/seaweedfs/seaweedfs.git
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Chris Lu
b872d5e683
* balance: extract the bytes-aware density metric to weed/topology/balancer The shell's volume.balance ranks servers by a bytes-aware density (used volume equivalents over free capacity). Move that math into the shared balancer package (VolumeDensity / DensityRatio / DensityNextRatio) so the maintenance worker can adopt the same metric next. Shell behavior is unchanged. * balance: rank a server with no free capacity as the fullest DensityRatio/DensityNextRatio divided by capacity, so a server past its slot limit (negative capacity) returned a negative ratio and sorted as the emptiest under ascending consumers — the opposite of reality. Treat any non-positive capacity (full, or overfull mid-run after receiving volumes) as the fullest (+Inf) so it is a move source, never a target. Covered by negative-capacity and ordering tests.
53 lines
2.2 KiB
Go
53 lines
2.2 KiB
Go
package balancer
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import "math"
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// zeroVolumeDensityWeight is the ratio given to a server holding no data, so it
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// still ranks below any loaded server (which has ratio >= 1) but is distinguished
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// from a server with unknown capacity.
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const zeroVolumeDensityWeight = 0.5
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// UsedVolumeEquivalents converts the bytes a server holds into whole-volume
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// equivalents (volumeBytes / volumeSizeLimit). Returns 0 when the limit is unset.
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func UsedVolumeEquivalents(volumeBytes, volumeSizeLimitBytes uint64) uint64 {
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if volumeSizeLimitBytes == 0 {
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return 0
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}
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return volumeBytes / volumeSizeLimitBytes
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}
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// VolumeDensity is the bytes-aware capacity view balancing ranks servers by:
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// used = volumeBytes / volumeSizeLimit, capacity = maxVolumeCount - used. Using
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// real data (not just volume count) means an over-configured maxVolumeCount can't
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// make a byte-full server look empty. capacity may be <= 0 for a server already
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// past its configured slots.
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func VolumeDensity(maxVolumeCount int64, volumeBytes, volumeSizeLimitBytes uint64) (capacity float64, usedVolumes uint64) {
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usedVolumes = UsedVolumeEquivalents(volumeBytes, volumeSizeLimitBytes)
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return float64(maxVolumeCount - int64(usedVolumes)), usedVolumes
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}
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// DensityRatio is a server's load: usedVolumes / capacity, higher = fuller. An
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// empty server gets a small positive ratio so it sorts below loaded servers.
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// A server with no free capacity (capacity <= 0: full, or over its configured
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// slots so capacity is negative) ranks as the fullest (+Inf), so ascending
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// consumers treat it as a move source and never as the emptiest target.
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func DensityRatio(capacity float64, usedVolumes uint64) float64 {
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if capacity <= 0 {
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return math.Inf(1)
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}
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if usedVolumes == 0 {
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return zeroVolumeDensityWeight / capacity
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}
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return float64(usedVolumes) / capacity
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}
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// DensityNextRatio is a server's load after one more volume lands on it:
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// (usedVolumes+1) / capacity. Used to test whether a move would overshoot. A
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// server with no free capacity (capacity <= 0) ranks as the fullest (+Inf).
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func DensityNextRatio(capacity float64, usedVolumes uint64) float64 {
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if capacity <= 0 {
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return math.Inf(1)
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}
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return float64(usedVolumes+1) / capacity
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}
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