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https://github.com/seaweedfs/seaweedfs.git
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Chris Lu
ee54fd6c08
NewReplicaPlacementFromByte formatted the byte with fmt.Sprintf and parsed the result back, allocating a string and a ReplicaPlacement every call. The master calls it once per volume in every heartbeat, and keeps the pointer for the lifetime of the volume, so a cluster with 1.6M volume replicas carries 1.6M of these where a handful of distinct values exist. The table is a flat pointer-free array, so it costs 6KB of static data and no heap objects however few placements a cluster actually uses. A byte only ever decodes to a valid placement, so the table is complete and the error return stays nil. BenchmarkSyncDataNodeRegistration/100000Volumes 500601 allocs/op -> 300589 allocs/op
127 lines
3.3 KiB
Go
127 lines
3.3 KiB
Go
package super_block
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import (
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"fmt"
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"github.com/seaweedfs/seaweedfs/weed/glog"
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)
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type ReplicaPlacement struct {
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SameRackCount int `json:"node,omitempty"`
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DiffRackCount int `json:"rack,omitempty"`
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DiffDataCenterCount int `json:"dc,omitempty"`
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}
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func NewReplicaPlacementFromString(t string) (*ReplicaPlacement, error) {
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rp := &ReplicaPlacement{}
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switch len(t) {
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case 0:
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t = "000"
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case 1:
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t = "00" + t
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case 2:
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t = "0" + t
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}
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for i, c := range t {
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count := int(c - '0')
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if count < 0 {
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return rp, fmt.Errorf("unknown replication type: %s", t)
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}
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switch i {
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case 0:
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rp.DiffDataCenterCount = count
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case 1:
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rp.DiffRackCount = count
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case 2:
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rp.SameRackCount = count
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}
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}
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value := rp.DiffDataCenterCount*100 + rp.DiffRackCount*10 + rp.SameRackCount
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if value > 255 {
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return rp, fmt.Errorf("unexpected replication type: %s", t)
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}
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return rp, nil
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}
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// replicaPlacementsByByte is one 6KB pointer-free array covering every encoding
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// a byte can hold. The master decodes one per volume in every volume server
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// heartbeat and keeps it for the volume's lifetime, so handing out a shared
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// element keeps that path off fmt and off the heap entirely.
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//
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// Elements are immutable. Callers must not write through the returned pointer.
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var replicaPlacementsByByte [256]ReplicaPlacement
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func init() {
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for b := range replicaPlacementsByByte {
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replicaPlacementsByByte[b] = ReplicaPlacement{
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DiffDataCenterCount: b / 100,
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DiffRackCount: b / 10 % 10,
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SameRackCount: b % 10,
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}
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}
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}
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func NewReplicaPlacementFromByte(b byte) (*ReplicaPlacement, error) {
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return &replicaPlacementsByByte[b], nil
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}
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func (rp *ReplicaPlacement) HasReplication() bool {
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return rp.DiffDataCenterCount != 0 || rp.DiffRackCount != 0 || rp.SameRackCount != 0
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}
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func (a *ReplicaPlacement) Equals(b *ReplicaPlacement) bool {
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if a == nil || b == nil {
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return false
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}
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return (a.SameRackCount == b.SameRackCount &&
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a.DiffRackCount == b.DiffRackCount &&
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a.DiffDataCenterCount == b.DiffDataCenterCount)
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}
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func (rp *ReplicaPlacement) Byte() byte {
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if rp == nil {
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return 0
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}
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ret := rp.DiffDataCenterCount*100 + rp.DiffRackCount*10 + rp.SameRackCount
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return byte(ret)
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}
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func (rp *ReplicaPlacement) String() string {
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if rp == nil {
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return ""
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}
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b := make([]byte, 3)
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b[0] = byte(rp.DiffDataCenterCount + '0')
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b[1] = byte(rp.DiffRackCount + '0')
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b[2] = byte(rp.SameRackCount + '0')
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return string(b)
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}
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func (rp *ReplicaPlacement) GetCopyCount() int {
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return rp.DiffDataCenterCount + rp.DiffRackCount + rp.SameRackCount + 1
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}
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// ResolveReplicaPlacement picks the EC shard replica placement constraint: an
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// explicit spec wins; otherwise the cluster default (typically the master's
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// configured default replication). A missing, invalid, or zero-replication value
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// yields nil, meaning even spread / no constraint. Shared by EC encode, repair,
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// and balance so the three resolve replica placement identically.
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func ResolveReplicaPlacement(explicitSpec, clusterDefault string) *ReplicaPlacement {
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spec := explicitSpec
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if spec == "" {
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spec = clusterDefault
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}
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if spec == "" {
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return nil
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}
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rp, err := NewReplicaPlacementFromString(spec)
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if err != nil {
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glog.Warningf("ignoring invalid replica placement %q: %v", spec, err)
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return nil
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}
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if !rp.HasReplication() {
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return nil
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}
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return rp
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}
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