lotus/chain/events/tscache.go

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package events
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import (
"context"
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"golang.org/x/xerrors"
"github.com/filecoin-project/lotus/chain/types"
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)
type tsByHFunc func(context.Context, uint64, *types.TipSet) (*types.TipSet, error)
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// tipSetCache implements a simple ring-buffer cache to keep track of recent
// tipsets
type tipSetCache struct {
cache []*types.TipSet
start int
len int
storage tsByHFunc
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}
func newTSCache(cap int, storage tsByHFunc) *tipSetCache {
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return &tipSetCache{
cache: make([]*types.TipSet, cap),
start: 0,
len: 0,
storage: storage,
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}
}
func (tsc *tipSetCache) add(ts *types.TipSet) error {
if tsc.len > 0 {
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if tsc.cache[tsc.start].Height() >= ts.Height() {
return xerrors.Errorf("tipSetCache.add: expected new tipset height to be at least %d, was %d", tsc.cache[tsc.start].Height()+1, ts.Height())
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}
}
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nextH := ts.Height()
if tsc.len > 0 {
nextH = tsc.cache[tsc.start].Height() + 1
}
// fill null blocks
for nextH != ts.Height() {
tsc.start = normalModulo(tsc.start+1, len(tsc.cache))
tsc.cache[tsc.start] = nil
if tsc.len < len(tsc.cache) {
tsc.len++
}
nextH++
}
tsc.start = normalModulo(tsc.start+1, len(tsc.cache))
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tsc.cache[tsc.start] = ts
if tsc.len < len(tsc.cache) {
tsc.len++
}
return nil
}
func (tsc *tipSetCache) revert(ts *types.TipSet) error {
if tsc.len == 0 {
return xerrors.New("tipSetCache.revert: nothing to revert; cache is empty")
}
if !tsc.cache[tsc.start].Equals(ts) {
return xerrors.New("tipSetCache.revert: revert tipset didn't match cache head")
}
tsc.cache[tsc.start] = nil
tsc.start = normalModulo(tsc.start-1, len(tsc.cache))
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tsc.len--
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_ = tsc.revert(nil) // revert null block gap
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return nil
}
func (tsc *tipSetCache) getNonNull(height uint64) (*types.TipSet, error) {
for {
ts, err := tsc.get(height)
if err != nil {
return nil, err
}
if ts != nil {
return ts, nil
}
height++
}
}
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func (tsc *tipSetCache) get(height uint64) (*types.TipSet, error) {
if tsc.len == 0 {
return nil, xerrors.New("tipSetCache.get: cache is empty")
}
headH := tsc.cache[tsc.start].Height()
if height > headH {
return nil, xerrors.Errorf("tipSetCache.get: requested tipset not in cache (req: %d, cache head: %d)", height, headH)
}
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clen := len(tsc.cache)
var tail *types.TipSet
for i := 1; i <= tsc.len; i++ {
tail = tsc.cache[normalModulo(tsc.start-tsc.len+i, clen)]
if tail != nil {
break
}
}
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if height < tail.Height() {
log.Warnf("tipSetCache.get: requested tipset not in cache, requesting from storage (h=%d; tail=%d)", height, tail.Height())
return tsc.storage(context.TODO(), height, tail)
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}
return tsc.cache[normalModulo(tsc.start-int(headH-height), clen)], nil
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}
func (tsc *tipSetCache) best() *types.TipSet {
return tsc.cache[tsc.start]
}
func normalModulo(n, m int) int {
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return ((n % m) + m) % m
}