122 lines
2.7 KiB
Go
122 lines
2.7 KiB
Go
package nomad
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import (
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"sort"
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"sync"
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"time"
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"github.com/hashicorp/go-msgpack/codec"
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)
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// TimeTable is used to associate a Raft index with a timestamp.
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// This is used so that we can quickly go from a timestamp to an
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// index or visa versa.
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type TimeTable struct {
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granularity time.Duration
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limit time.Duration
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table []TimeTableEntry
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l sync.RWMutex
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}
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// TimeTableEntry is used to track a time and index
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type TimeTableEntry struct {
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Index uint64
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Time time.Time
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}
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// NewTimeTable creates a new time table which stores entries
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// at a given granularity for a maximum limit. The storage space
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// required is (limit/granularity)
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func NewTimeTable(granularity time.Duration, limit time.Duration) *TimeTable {
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size := limit / granularity
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if size < 1 {
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size = 1
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}
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t := &TimeTable{
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granularity: granularity,
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limit: limit,
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table: make([]TimeTableEntry, 1, size),
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}
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return t
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}
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// Serialize is used to serialize the time table
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func (t *TimeTable) Serialize(enc *codec.Encoder) error {
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t.l.RLock()
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defer t.l.RUnlock()
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return enc.Encode(t.table)
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}
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// Deserialize is used to deserialize the time table
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// and restore the state
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func (t *TimeTable) Deserialize(dec *codec.Decoder) error {
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// Decode the table
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var table []TimeTableEntry
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if err := dec.Decode(&table); err != nil {
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return err
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}
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// Witness from oldest to newest
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n := len(table)
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for i := n - 1; i >= 0; i-- {
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t.Witness(table[i].Index, table[i].Time)
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}
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return nil
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}
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// Witness is used to witness a new index and time.
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func (t *TimeTable) Witness(index uint64, when time.Time) {
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t.l.Lock()
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defer t.l.Unlock()
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// Ensure monotonic indexes
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if t.table[0].Index > index {
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return
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}
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// Skip if we already have a recent enough entry
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if when.Sub(t.table[0].Time) < t.granularity {
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return
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}
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// Grow the table if we haven't reached the size
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if len(t.table) < cap(t.table) {
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t.table = append(t.table, TimeTableEntry{})
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}
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// Add this entry
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copy(t.table[1:], t.table[:len(t.table)-1])
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t.table[0].Index = index
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t.table[0].Time = when
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}
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// NearestIndex returns the nearest index older than the given time
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func (t *TimeTable) NearestIndex(when time.Time) uint64 {
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t.l.RLock()
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defer t.l.RUnlock()
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n := len(t.table)
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idx := sort.Search(n, func(i int) bool {
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return !t.table[i].Time.After(when)
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})
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if idx < n && idx >= 0 {
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return t.table[idx].Index
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}
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return 0
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}
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// NearestTime returns the nearest time older than the given index
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func (t *TimeTable) NearestTime(index uint64) time.Time {
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t.l.RLock()
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defer t.l.RUnlock()
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n := len(t.table)
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idx := sort.Search(n, func(i int) bool {
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return t.table[i].Index <= index
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})
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if idx < n && idx >= 0 {
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return t.table[idx].Time
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}
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return time.Time{}
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}
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