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prefetcher.go
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prefetcher.go
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// Copyright 2016 Keybase Inc. All rights reserved.
// Use of this source code is governed by a BSD
// license that can be found in the LICENSE file.
package libkbfs
import (
"fmt"
"sort"
"sync"
"time"
"github.com/eapache/channels"
"github.com/keybase/backoff"
"github.com/keybase/client/go/kbfs/data"
"github.com/keybase/client/go/kbfs/kbfsblock"
"github.com/keybase/client/go/kbfs/libkey"
"github.com/keybase/client/go/kbfs/tlf"
"github.com/keybase/client/go/libkb"
"github.com/keybase/client/go/logger"
"github.com/keybase/client/go/protocol/keybase1"
"github.com/pkg/errors"
"golang.org/x/net/context"
)
const (
updatePointerPrefetchPriority int = 1
prefetchTimeout time.Duration = 24 * time.Hour
overallSyncStatusInterval time.Duration = 1 * time.Second
)
type prefetcherConfig interface {
syncedTlfGetterSetter
data.Versioner
logMaker
blockCacher
diskBlockCacheGetter
clockGetter
reporterGetter
settingsDBGetter
}
type prefetchRequest struct {
ptr data.BlockPointer
encodedSize uint32
newBlock func() data.Block
kmd libkey.KeyMetadata
priority int
lifetime data.BlockCacheLifetime
prefetchStatus PrefetchStatus
action BlockRequestAction
sendCh chan<- <-chan struct{}
// obseleted is a channel that can be used to cancel this request while
// it is waiting in the queue if the prefetch is no longer necessary.
obseleted <-chan struct{}
// countedInOverall is true if the bytes of this block are counted
// in the overall sync status byte total currently.
countedInOverall bool
}
type ctxPrefetcherTagKey int
const (
ctxPrefetcherIDKey ctxPrefetcherTagKey = iota
ctxPrefetchIDKey
ctxPrefetcherID = "PREID"
ctxPrefetchID = "PFID"
)
type prefetch struct {
subtreeBlockCount int
subtreeTriggered bool
subtreeRetrigger bool
req *prefetchRequest
// Each refnonce for this block ID can have a different set of
// parents. Track the channel for the specific instance of the
// prefetch that counted us in its progress (since a parent may be
// canceled and rescheduled later).
parents map[kbfsblock.RefNonce]map[data.BlockPointer]<-chan struct{}
ctx context.Context
cancel context.CancelFunc
waitCh chan struct{}
PrefetchProgress
}
func (p *prefetch) Close() {
select {
case <-p.waitCh:
default:
close(p.waitCh)
}
p.cancel()
}
type rescheduledPrefetch struct {
off backoff.BackOff
timer *time.Timer
}
type queuedPrefetch struct {
waitingPrefetches int
channel chan struct{}
tlfID tlf.ID
}
type cancelTlfPrefetch struct {
tlfID tlf.ID
channel chan<- struct{}
}
type blockPrefetcher struct {
ctx context.Context
config prefetcherConfig
log logger.Logger
vlog *libkb.VDebugLog
makeNewBackOff func() backoff.BackOff
// blockRetriever to retrieve blocks from the server
retriever BlockRetriever
// channel to request prefetches
prefetchRequestCh channels.Channel
// channel to cancel prefetches
prefetchCancelCh channels.Channel
// channel to cancel all prefetches for a TLF
prefetchCancelTlfCh channels.Channel
// channel to reschedule prefetches
prefetchRescheduleCh channels.Channel
// channel to get prefetch status
prefetchStatusCh channels.Channel
// channel to allow synchronization on completion
inFlightFetches channels.Channel
// protects shutdownCh
shutdownOnce sync.Once
// channel that is idempotently closed when a shutdown occurs
shutdownCh chan struct{}
// channel that is closed when all current fetches are done and prefetches
// have been triggered
almostDoneCh chan struct{}
// channel that is closed when a shutdown completes and all pending
// prefetch requests are complete
doneCh chan struct{}
// map to store prefetch metadata
prefetches map[kbfsblock.ID]*prefetch
// map to store backoffs for rescheduling top blocks
rescheduled map[kbfsblock.ID]*rescheduledPrefetch
// channel that's always closed, to avoid overhead on certain requests
closedCh <-chan struct{}
// map to channels for cancelling queued prefetches
queuedPrefetchHandlesLock sync.Mutex
queuedPrefetchHandles map[data.BlockPointer]queuedPrefetch
// Tracks the overall bytes currently being prefetched to the sync
// cache. The total outstanding bytes resets on the first new
// prefetch after a completion happens.
overallSyncStatusLock sync.RWMutex
overallSyncStatus PrefetchProgress
lastOverallSyncStatusSent time.Time
}
var _ Prefetcher = (*blockPrefetcher)(nil)
func defaultBackOffForPrefetcher() backoff.BackOff {
return backoff.NewExponentialBackOff()
}
func newBlockPrefetcher(retriever BlockRetriever,
config prefetcherConfig, testSyncCh <-chan struct{},
testDoneCh chan<- struct{}) *blockPrefetcher {
closedCh := make(chan struct{})
close(closedCh)
p := &blockPrefetcher{
config: config,
makeNewBackOff: defaultBackOffForPrefetcher,
retriever: retriever,
prefetchRequestCh: NewInfiniteChannelWrapper(),
prefetchCancelCh: NewInfiniteChannelWrapper(),
prefetchCancelTlfCh: NewInfiniteChannelWrapper(),
prefetchRescheduleCh: NewInfiniteChannelWrapper(),
prefetchStatusCh: NewInfiniteChannelWrapper(),
inFlightFetches: NewInfiniteChannelWrapper(),
shutdownCh: make(chan struct{}),
almostDoneCh: make(chan struct{}, 1),
doneCh: make(chan struct{}),
prefetches: make(map[kbfsblock.ID]*prefetch),
queuedPrefetchHandles: make(map[data.BlockPointer]queuedPrefetch),
rescheduled: make(map[kbfsblock.ID]*rescheduledPrefetch),
closedCh: closedCh,
}
if config != nil {
p.log = config.MakeLogger("PRE")
p.vlog = config.MakeVLogger(p.log)
} else {
p.log = logger.NewNull()
p.vlog = libkb.NewVDebugLog(p.log)
}
p.ctx = CtxWithRandomIDReplayable(context.Background(), ctxPrefetcherIDKey,
ctxPrefetcherID, p.log)
if retriever == nil {
// If we pass in a nil retriever, this prefetcher shouldn't do
// anything. Treat it as already shut down.
p.Shutdown()
close(p.doneCh)
} else {
go p.run(testSyncCh, testDoneCh)
go p.shutdownLoop()
}
return p
}
func (p *blockPrefetcher) sendOverallSyncStatusHelperLocked() {
var status keybase1.FolderSyncStatus
status.PrefetchProgress = p.overallSyncStatus.ToProtocolProgress(
p.config.Clock())
FillInDiskSpaceStatus(
context.Background(), &status, p.overallSyncStatus.ToProtocolStatus(),
p.config.DiskBlockCache())
p.config.Reporter().NotifyOverallSyncStatus(context.Background(), status)
p.lastOverallSyncStatusSent = p.config.Clock().Now()
}
func (p *blockPrefetcher) sendOverallSyncStatusLocked() {
// Don't send a new status notification if we aren't complete, and
// if we have sent one within the last interval.
if p.overallSyncStatus.SubtreeBytesFetched !=
p.overallSyncStatus.SubtreeBytesTotal &&
p.config.Clock().Now().Before(
p.lastOverallSyncStatusSent.Add(overallSyncStatusInterval)) {
return
}
p.sendOverallSyncStatusHelperLocked()
}
func (p *blockPrefetcher) incOverallSyncTotalBytes(req *prefetchRequest) {
if !req.action.Sync() || req.countedInOverall {
return
}
p.overallSyncStatusLock.Lock()
defer p.overallSyncStatusLock.Unlock()
if p.overallSyncStatus.SubtreeBytesFetched ==
p.overallSyncStatus.SubtreeBytesTotal {
// Reset since we had already finished syncing.
p.overallSyncStatus = PrefetchProgress{}
p.overallSyncStatus.Start = p.config.Clock().Now()
}
p.overallSyncStatus.SubtreeBytesTotal += uint64(req.encodedSize)
req.countedInOverall = true
p.sendOverallSyncStatusLocked()
}
func (p *blockPrefetcher) decOverallSyncTotalBytes(req *prefetchRequest) {
if !req.action.Sync() || !req.countedInOverall {
return
}
p.overallSyncStatusLock.Lock()
defer p.overallSyncStatusLock.Unlock()
if p.overallSyncStatus.SubtreeBytesTotal < uint64(req.encodedSize) {
// Both log and panic so that we get the PFID in the log.
p.log.CErrorf(
context.TODO(), "panic: decOverallSyncTotalBytes overstepped "+
"its bounds (bytes=%d, fetched=%d, total=%d)", req.encodedSize,
p.overallSyncStatus.SubtreeBytesFetched,
p.overallSyncStatus.SubtreeBytesTotal)
panic("decOverallSyncTotalBytes overstepped its bounds")
}
p.overallSyncStatus.SubtreeBytesTotal -= uint64(req.encodedSize)
req.countedInOverall = false
p.sendOverallSyncStatusLocked()
}
func (p *blockPrefetcher) incOverallSyncFetchedBytes(req *prefetchRequest) {
if !req.action.Sync() || !req.countedInOverall {
return
}
p.overallSyncStatusLock.Lock()
defer p.overallSyncStatusLock.Unlock()
p.overallSyncStatus.SubtreeBytesFetched += uint64(req.encodedSize)
req.countedInOverall = false
p.sendOverallSyncStatusLocked()
if p.overallSyncStatus.SubtreeBytesFetched >
p.overallSyncStatus.SubtreeBytesTotal {
// Both log and panic so that we get the PFID in the log.
p.log.CErrorf(
context.TODO(), "panic: incOverallSyncFetchedBytes overstepped "+
"its bounds (fetched=%d, total=%d)",
p.overallSyncStatus.SubtreeBytesFetched,
p.overallSyncStatus.SubtreeBytesTotal)
panic("incOverallSyncFetchedBytes overstepped its bounds")
}
}
func (p *blockPrefetcher) newPrefetch(
count int, bytes uint64, triggered bool,
req *prefetchRequest) *prefetch {
ctx, cancel := context.WithTimeout(p.ctx, prefetchTimeout)
ctx = CtxWithRandomIDReplayable(
ctx, ctxPrefetchIDKey, ctxPrefetchID, p.log)
p.incOverallSyncTotalBytes(req)
return &prefetch{
subtreeBlockCount: count,
subtreeTriggered: triggered,
req: req,
parents: make(map[kbfsblock.RefNonce]map[data.BlockPointer]<-chan struct{}),
ctx: ctx,
cancel: cancel,
waitCh: make(chan struct{}),
PrefetchProgress: PrefetchProgress{
SubtreeBytesTotal: bytes,
Start: p.config.Clock().Now(),
},
}
}
func (p *blockPrefetcher) getParentForApply(
pptr data.BlockPointer, refMap map[data.BlockPointer]<-chan struct{},
ch <-chan struct{}) *prefetch {
// Check if the particular prefetch for our parent that we're
// tracking has already completed or been canceled, and if so,
// don't apply to that parent. This can happen in the following
// scenario:
//
// * A path `a/b/c` gets prefetched.
// * The path gets updated via another write to `a'/b'/c`.
// * `a` and `b` get canceled.
// * `a` gets re-fetched, and `b` gets added to the prefetch list.
// * `c` completes and tries to complete its old parent `b`, which
// prematurely closes the new prefetches for `b` and `c` (which
// are now only expecting one block, the new `b` prefetch).
parentDone := false
select {
case <-ch:
parentDone = true
default:
}
parent, ok := p.prefetches[pptr.ID]
if parentDone || !ok {
// Note that the parent (or some other ancestor) might be
// rescheduled for later and have been removed from
// `prefetches`. In that case still delete it from the
// `parents` list as normal; the reschedule will add it
// back in later as needed.
delete(refMap, pptr)
return nil
}
return parent
}
// applyToPtrParentsRecursive applies a function just to the parents
// of the specific pointer (with refnonce).
func (p *blockPrefetcher) applyToPtrParentsRecursive(
f func(data.BlockPointer, *prefetch), ptr data.BlockPointer, pre *prefetch) {
defer func() {
if r := recover(); r != nil {
id := kbfsblock.ZeroID
if pre.req != nil {
id = pre.req.ptr.ID
}
p.log.CErrorf(pre.ctx, "Next prefetch in panic unroll: id=%s, "+
"subtreeBlockCount=%d, subtreeTriggered=%t, parents=%+v",
id, pre.subtreeBlockCount, pre.subtreeTriggered, pre.parents)
panic(r)
}
}()
refMap := pre.parents[ptr.RefNonce]
for pptr, ch := range refMap {
parent := p.getParentForApply(pptr, refMap, ch)
if parent != nil {
p.applyToPtrParentsRecursive(f, pptr, parent)
}
}
if len(pre.parents[ptr.RefNonce]) == 0 {
delete(pre.parents, ptr.RefNonce)
}
f(ptr, pre)
}
// applyToParentsRecursive applies a function to all the parents of
// the pointer (with any refnonces).
func (p *blockPrefetcher) applyToParentsRecursive(
f func(kbfsblock.ID, *prefetch), blockID kbfsblock.ID, pre *prefetch) {
defer func() {
if r := recover(); r != nil {
id := kbfsblock.ZeroID
if pre.req != nil {
id = pre.req.ptr.ID
}
p.log.CErrorf(pre.ctx, "Next prefetch in panic unroll: id=%s, "+
"subtreeBlockCount=%d, subtreeTriggered=%t, parents=%+v",
id, pre.subtreeBlockCount, pre.subtreeTriggered, pre.parents)
panic(r)
}
}()
for refNonce, refMap := range pre.parents {
for pptr, ch := range refMap {
parent := p.getParentForApply(pptr, refMap, ch)
if parent != nil {
p.applyToParentsRecursive(f, pptr.ID, parent)
}
}
if len(refMap) == 0 {
delete(pre.parents, refNonce)
}
}
f(blockID, pre)
}
func (p *blockPrefetcher) getBlockSynchronously(
ctx context.Context, req *prefetchRequest, action BlockRequestAction) (
data.Block, error) {
// Avoid the overhead of the block retriever copy if possible.
cachedBlock, err := p.config.BlockCache().Get(req.ptr)
if err == nil {
return cachedBlock, nil
}
b := req.newBlock()
err = <-p.retriever.Request(
ctx, defaultOnDemandRequestPriority, req.kmd, req.ptr,
b, req.lifetime, action)
if err != nil {
return nil, err
}
return b, nil
}
// Walk up the block tree decrementing each node by `numBlocks`. Any
// zeroes we hit get marked complete and deleted. Also, count
// `numBytes` bytes as being fetched. If the block count becomes 0,
// then the total number of bytes must now be fetched.
// TODO: If we ever hit a lower number than the child, panic.
func (p *blockPrefetcher) completePrefetch(
numBlocks int, numBytes uint64) func(kbfsblock.ID, *prefetch) {
return func(blockID kbfsblock.ID, pp *prefetch) {
pp.subtreeBlockCount -= numBlocks
pp.SubtreeBytesFetched += numBytes
if pp.subtreeBlockCount < 0 {
// Both log and panic so that we get the PFID in the log.
p.log.CErrorf(pp.ctx, "panic: completePrefetch overstepped its "+
"bounds")
panic("completePrefetch overstepped its bounds")
}
if pp.req == nil {
p.log.CErrorf(pp.ctx, "panic: completePrefetch got a nil req "+
"for block %s", blockID)
panic("completePrefetch got a nil req")
}
if pp.subtreeBlockCount == 0 {
if pp.SubtreeBytesFetched != pp.SubtreeBytesTotal {
panic(fmt.Sprintf("Bytes fetch mismatch: fetched=%d, total=%d",
pp.SubtreeBytesFetched, pp.SubtreeBytesTotal))
}
delete(p.prefetches, blockID)
p.clearRescheduleState(blockID)
delete(p.rescheduled, blockID)
defer pp.Close()
b, err := p.getBlockSynchronously(pp.ctx, pp.req, BlockRequestSolo)
if err != nil {
p.log.CWarningf(pp.ctx, "failed to retrieve block to "+
"complete its prefetch, canceled it instead: %+v", err)
return
}
err = p.retriever.PutInCaches(pp.ctx, pp.req.ptr,
pp.req.kmd.TlfID(), b, pp.req.lifetime,
FinishedPrefetch, pp.req.action.CacheType())
if err != nil {
p.log.CWarningf(pp.ctx, "failed to complete prefetch due to "+
"cache error, canceled it instead: %+v", err)
}
}
}
}
func (p *blockPrefetcher) decrementPrefetch(blockID kbfsblock.ID, pp *prefetch) {
pp.subtreeBlockCount--
if pp.subtreeBlockCount < 0 {
// Both log and panic so that we get the PFID in the log.
p.log.CErrorf(pp.ctx, "panic: decrementPrefetch overstepped its bounds")
panic("decrementPrefetch overstepped its bounds")
}
}
func (p *blockPrefetcher) addFetchedBytes(bytes uint64) func(
kbfsblock.ID, *prefetch) {
return func(blockID kbfsblock.ID, pp *prefetch) {
pp.SubtreeBytesFetched += bytes
if pp.SubtreeBytesFetched > pp.SubtreeBytesTotal {
// Both log and panic so that we get the PFID in the log.
p.log.CErrorf(pp.ctx, "panic: addFetchedBytes overstepped "+
"its bounds (fetched=%d, total=%d)", pp.SubtreeBytesFetched,
pp.SubtreeBytesTotal)
panic("addFetchedBytes overstepped its bounds")
}
}
}
func (p *blockPrefetcher) clearRescheduleState(blockID kbfsblock.ID) {
rp, ok := p.rescheduled[blockID]
if !ok {
return
}
if rp.timer != nil {
rp.timer.Stop()
rp.timer = nil
}
}
func (p *blockPrefetcher) cancelQueuedPrefetch(ptr data.BlockPointer) {
p.queuedPrefetchHandlesLock.Lock()
defer p.queuedPrefetchHandlesLock.Unlock()
qp, ok := p.queuedPrefetchHandles[ptr]
if ok {
close(qp.channel)
delete(p.queuedPrefetchHandles, ptr)
p.log.Debug("cancelled queued prefetch for block %s", ptr)
} else {
p.vlog.Log(libkb.VLog2, "nothing to cancel for block %s", ptr)
}
}
func (p *blockPrefetcher) cancelQueuedPrefetchesForTlf(tlfID tlf.ID) {
p.queuedPrefetchHandlesLock.Lock()
defer p.queuedPrefetchHandlesLock.Unlock()
for ptr, qp := range p.queuedPrefetchHandles {
if qp.tlfID != tlfID {
continue
}
p.vlog.Log(
libkb.VLog2, "Canceling queued prefetch for %s, tlf=%s", ptr, tlfID)
close(qp.channel)
delete(p.queuedPrefetchHandles, ptr)
}
}
func (p *blockPrefetcher) markQueuedPrefetchDone(ptr data.BlockPointer) {
p.queuedPrefetchHandlesLock.Lock()
defer p.queuedPrefetchHandlesLock.Unlock()
qp, present := p.queuedPrefetchHandles[ptr]
if !present {
p.vlog.CLogf(
context.Background(), libkb.VLog2, "queuedPrefetch not present in"+
" queuedPrefetchHandles: %s", ptr)
return
}
if qp.waitingPrefetches == 1 {
delete(p.queuedPrefetchHandles, ptr)
} else {
p.queuedPrefetchHandles[ptr] = queuedPrefetch{
qp.waitingPrefetches - 1, qp.channel, qp.tlfID}
}
}
func (p *blockPrefetcher) doCancel(id kbfsblock.ID, pp *prefetch) {
p.decOverallSyncTotalBytes(pp.req)
delete(p.prefetches, id)
pp.Close()
p.clearRescheduleState(id)
delete(p.rescheduled, id)
}
func (p *blockPrefetcher) cancelPrefetch(ptr data.BlockPointer, pp *prefetch) {
delete(pp.parents, ptr.RefNonce)
if len(pp.parents) > 0 {
return
}
p.doCancel(ptr.ID, pp)
}
// shutdownLoop tracks in-flight requests
func (p *blockPrefetcher) shutdownLoop() {
top:
for {
select {
case chInterface := <-p.inFlightFetches.Out():
ch := chInterface.(<-chan error)
<-ch
case <-p.shutdownCh:
break top
}
}
for p.inFlightFetches.Len() > 0 {
chInterface := <-p.inFlightFetches.Out()
ch := chInterface.(<-chan error)
<-ch
}
p.almostDoneCh <- struct{}{}
}
// calculatePriority returns either a base priority for an unsynced TLF or a
// high priority for a synced TLF.
func (p *blockPrefetcher) calculatePriority(
basePriority int, action BlockRequestAction) int {
// A prefetched, non-deep-synced child always gets throttled for
// now, until we fix the database performance issues.
if basePriority > throttleRequestPriority && !action.DeepSync() {
basePriority = throttleRequestPriority
}
return basePriority - 1
}
// removeFinishedParent removes a parent from the given refmap if it's
// finished or is otherwise no longer a prefetch in progress.
func (p *blockPrefetcher) removeFinishedParent(
pptr data.BlockPointer, refMap map[data.BlockPointer]<-chan struct{},
ch <-chan struct{}) {
_ = p.getParentForApply(pptr, refMap, ch)
}
// request maps the parent->child block relationship in the prefetcher, and it
// triggers child prefetches that aren't already in progress.
func (p *blockPrefetcher) request(ctx context.Context, priority int,
kmd libkey.KeyMetadata, info data.BlockInfo, block data.Block,
lifetime data.BlockCacheLifetime, parentPtr data.BlockPointer,
isParentNew bool, action BlockRequestAction,
idsSeen map[kbfsblock.ID]bool) (
numBlocks int, numBytesFetched, numBytesTotal uint64) {
ptr := info.BlockPointer
if idsSeen[ptr.ID] {
return 0, 0, 0
}
idsSeen[ptr.ID] = true
// If the prefetch is already waiting, don't make it wait again.
// Add the parent, however.
pre, isPrefetchWaiting := p.prefetches[ptr.ID]
if !isPrefetchWaiting {
// If the block isn't in the tree, we add it with a block count of 1 (a
// later TriggerPrefetch will come in and decrement it).
obseleted := make(chan struct{})
req := &prefetchRequest{
ptr, info.EncodedSize, block.NewEmptier(), kmd, priority,
lifetime, NoPrefetch, action, nil, obseleted, false}
pre = p.newPrefetch(1, uint64(info.EncodedSize), false, req)
p.prefetches[ptr.ID] = pre
}
// If this is a new prefetch, or if we need to update the action,
// send a new request.
newAction := action.Combine(pre.req.action)
if !isPrefetchWaiting || pre.req.action != newAction || pre.req.ptr != ptr {
// Update the action to prevent any early cancellation of a
// previous, non-deeply-synced request, and trigger a new
// request in case the previous request has already been
// handled.
oldAction := pre.req.action
pre.req.action = newAction
if !oldAction.Sync() && newAction.Sync() {
p.incOverallSyncTotalBytes(pre.req)
// Delete the old parent waitCh if it's been canceled already.
if ch, ok := pre.parents[ptr.RefNonce][parentPtr]; ok {
p.removeFinishedParent(parentPtr, pre.parents[ptr.RefNonce], ch)
}
if pre.subtreeTriggered {
// Since this fetch is being converted into a sync, we
// need to re-trigger all the child fetches to be
// syncs as well.
pre.subtreeRetrigger = true
}
}
ch := p.retriever.Request(
pre.ctx, priority, kmd, ptr, block.NewEmpty(), lifetime,
action.DelayedCacheCheckAction())
p.inFlightFetches.In() <- ch
}
parentPre, isParentWaiting := p.prefetches[parentPtr.ID]
if !isParentWaiting {
p.vlog.CLogf(pre.ctx, libkb.VLog2,
"prefetcher doesn't know about parent block "+
"%s for child block %s", parentPtr, ptr.ID)
panic("prefetcher doesn't know about parent block when trying to " +
"record parent-child relationship")
}
if pre.parents[ptr.RefNonce][parentPtr] == nil || isParentNew {
// The new parent needs its subtree block count increased. This can
// happen either when:
// 1. The child doesn't know about the parent when the child is first
// created above, or the child was previously in the tree but the
// parent was not (e.g. when there's an updated parent due to a change
// in a sibling of this child).
// 2. The parent is newly created but the child _did_ know about it,
// like when the parent previously had a prefetch but was canceled.
if len(pre.parents[ptr.RefNonce]) == 0 {
pre.parents[ptr.RefNonce] = make(map[data.BlockPointer]<-chan struct{})
}
pre.parents[ptr.RefNonce][parentPtr] = parentPre.waitCh
if pre.subtreeBlockCount > 0 {
p.vlog.CLogf(ctx, libkb.VLog2,
"Prefetching %v, action=%s, numBlocks=%d, isParentNew=%t",
ptr, action, pre.subtreeBlockCount, isParentNew)
}
return pre.subtreeBlockCount, pre.SubtreeBytesFetched,
pre.SubtreeBytesTotal
}
return 0, 0, 0
}
func (p *blockPrefetcher) handleStatusRequest(req *prefetchStatusRequest) {
pre, isPrefetchWaiting := p.prefetches[req.ptr.ID]
if !isPrefetchWaiting {
req.ch <- PrefetchProgress{}
} else {
req.ch <- pre.PrefetchProgress
}
}
// handleCriticalRequests should be called periodically during any
// long prefetch requests, to make sure we handle critical requests
// quickly. These are requests that are required to be run in the
// main processing goroutine, but won't interfere with whatever
// request we're in the middle of.
func (p *blockPrefetcher) handleCriticalRequests() {
for {
// Fulfill any status requests since the user could be waiting
// for them.
select {
case req := <-p.prefetchStatusCh.Out():
p.handleStatusRequest(req.(*prefetchStatusRequest))
default:
return
}
}
}
func (p *blockPrefetcher) prefetchIndirectFileBlock(
ctx context.Context, parentPtr data.BlockPointer, b *data.FileBlock,
kmd libkey.KeyMetadata, lifetime data.BlockCacheLifetime, isPrefetchNew bool,
action BlockRequestAction, basePriority int) (
numBlocks int, numBytesFetched, numBytesTotal uint64, isTail bool) {
// Prefetch indirect block pointers.
newPriority := p.calculatePriority(basePriority, action)
idsSeen := make(map[kbfsblock.ID]bool, len(b.IPtrs))
for _, ptr := range b.IPtrs {
b, f, t := p.request(
ctx, newPriority, kmd, ptr.BlockInfo, b.NewEmpty(), lifetime,
parentPtr, isPrefetchNew, action, idsSeen)
numBlocks += b
numBytesFetched += f
numBytesTotal += t
p.handleCriticalRequests()
}
return numBlocks, numBytesFetched, numBytesTotal, len(b.IPtrs) == 0
}
func (p *blockPrefetcher) prefetchIndirectDirBlock(
ctx context.Context, parentPtr data.BlockPointer, b *data.DirBlock,
kmd libkey.KeyMetadata, lifetime data.BlockCacheLifetime, isPrefetchNew bool,
action BlockRequestAction, basePriority int) (
numBlocks int, numBytesFetched, numBytesTotal uint64, isTail bool) {
// Prefetch indirect block pointers.
newPriority := p.calculatePriority(basePriority, action)
idsSeen := make(map[kbfsblock.ID]bool, len(b.IPtrs))
for _, ptr := range b.IPtrs {
b, f, t := p.request(
ctx, newPriority, kmd, ptr.BlockInfo, b.NewEmpty(), lifetime,
parentPtr, isPrefetchNew, action, idsSeen)
numBlocks += b
numBytesFetched += f
numBytesTotal += t
p.handleCriticalRequests()
}
return numBlocks, numBytesFetched, numBytesTotal, len(b.IPtrs) == 0
}
func (p *blockPrefetcher) prefetchDirectDirBlock(
ctx context.Context, parentPtr data.BlockPointer, b *data.DirBlock,
kmd libkey.KeyMetadata, lifetime data.BlockCacheLifetime, isPrefetchNew bool,
action BlockRequestAction, basePriority int) (
numBlocks int, numBytesFetched, numBytesTotal uint64, isTail bool) {
// Prefetch all DirEntry root blocks.
dirEntries := data.DirEntriesBySizeAsc{
DirEntries: data.DirEntryMapToDirEntries(b.Children),
}
sort.Sort(dirEntries)
newPriority := p.calculatePriority(basePriority, action)
totalChildEntries := 0
idsSeen := make(map[kbfsblock.ID]bool, len(dirEntries.DirEntries))
for _, entry := range dirEntries.DirEntries {
var block data.Block
switch entry.Type {
case data.Dir:
block = &data.DirBlock{}
case data.File:
block = &data.FileBlock{}
case data.Exec:
block = &data.FileBlock{}
case data.Sym:
// Skip symbolic links because there's nothing to prefetch.
continue
default:
p.log.CDebugf(ctx, "Skipping prefetch for entry of "+
"unknown type %d", entry.Type)
continue
}
totalChildEntries++
b, f, t := p.request(
ctx, newPriority, kmd, entry.BlockInfo, block, lifetime,
parentPtr, isPrefetchNew, action, idsSeen)
numBlocks += b
numBytesFetched += f
numBytesTotal += t
p.handleCriticalRequests()
}
if totalChildEntries == 0 {
isTail = true
}
return numBlocks, numBytesFetched, numBytesTotal, isTail
}
// handlePrefetch allows the prefetcher to trigger prefetches. `run` calls this
// when a prefetch request is received and the criteria are satisfied to
// initiate a prefetch for this block's children.
// Returns `numBlocks` which indicates how many additional blocks (blocks not
// currently in the prefetch tree) with a parent of `pre.req.ptr.ID` must be
// added to the tree.
func (p *blockPrefetcher) handlePrefetch(
pre *prefetch, isPrefetchNew bool, action BlockRequestAction, b data.Block) (
numBlocks int, numBytesFetched, numBytesTotal uint64, isTail bool,
err error) {
req := pre.req
childAction := action.ChildAction(b)
switch b := b.(type) {
case *data.FileBlock:
if b.IsInd {
numBlocks, numBytesFetched, numBytesTotal, isTail =
p.prefetchIndirectFileBlock(
pre.ctx, req.ptr, b, req.kmd, req.lifetime,
isPrefetchNew, childAction, req.priority)
} else {
isTail = true
}
case *data.DirBlock:
if b.IsInd {
numBlocks, numBytesFetched, numBytesTotal, isTail =
p.prefetchIndirectDirBlock(
pre.ctx, req.ptr, b, req.kmd, req.lifetime,
isPrefetchNew, childAction, req.priority)
} else {
numBlocks, numBytesFetched, numBytesTotal, isTail =
p.prefetchDirectDirBlock(
pre.ctx, req.ptr, b, req.kmd, req.lifetime,
isPrefetchNew, childAction, req.priority)
}
default:
// Skipping prefetch for block of unknown type (likely CommonBlock)
return 0, 0, 0, false, errors.New("unknown block type")
}
return numBlocks, numBytesFetched, numBytesTotal, isTail, nil
}
func (p *blockPrefetcher) rescheduleTopBlock(
blockID kbfsblock.ID, pp *prefetch) {
// If this block has parents and thus is not a top-block, cancel
// all of the references for it.
if len(pp.parents) > 0 {
for refNonce := range pp.parents {
p.cancelPrefetch(data.BlockPointer{
ID: blockID,
Context: kbfsblock.Context{RefNonce: refNonce},
}, pp)
}
return
}
// Effectively below we are transferring the request for the top
// block from `p.prefetches` to `p.rescheduled`.
delete(p.prefetches, blockID)
pp.Close()
// Only reschedule the top-most blocks, which has no parents.
rp, ok := p.rescheduled[blockID]
if !ok {
rp = &rescheduledPrefetch{
off: p.makeNewBackOff(),
}
p.rescheduled[blockID] = rp
}
if rp.timer != nil {
// Prefetch already scheduled.
return
}
// Copy the req, re-using the same Block as before.
req := *pp.req
d := rp.off.NextBackOff()
if d == backoff.Stop {
p.log.Debug("Stopping rescheduling of %s due to stopped backoff timer",
blockID)
return
}
p.log.Debug("Rescheduling prefetch of %s in %s", blockID, d)
rp.timer = time.AfterFunc(d, func() {
p.triggerPrefetch(&req)
})
}
func (p *blockPrefetcher) reschedulePrefetch(req *prefetchRequest) {
select {
case p.prefetchRescheduleCh.In() <- req:
case <-p.shutdownCh:
p.log.Warning("Skipping prefetch reschedule for block %v since "+
"the prefetcher is shutdown", req.ptr.ID)
}
}
func (p *blockPrefetcher) sendOverallSyncStatusNotification() {
p.overallSyncStatusLock.Lock()
defer p.overallSyncStatusLock.Unlock()
p.sendOverallSyncStatusHelperLocked()
}
func (p *blockPrefetcher) stopIfNeeded(
ctx context.Context, req *prefetchRequest) (doStop, doCancel bool) {
dbc := p.config.DiskBlockCache()
if dbc == nil {
return false, false
}
hasRoom, howMuchRoom, err := dbc.DoesCacheHaveSpace(ctx, req.action.CacheType())
if err != nil {
p.log.CDebugf(ctx, "Error checking space: +%v", err)
return false, false
}
if hasRoom {
db := p.config.GetSettingsDB()
if db != nil {
if settings, err := db.Settings(ctx); err == nil &&
req.action.CacheType() == DiskBlockSyncCache &&
howMuchRoom < settings.SpaceAvailableNotificationThreshold {
// If a notification threshold is configured, we send a
// notificaiton here.
p.sendOverallSyncStatusNotification()
}
}
return false, false
}
defer func() {
if doStop {
p.vlog.CLogf(ctx, libkb.VLog2,
"stopping prefetch for block %s due to full cache (sync=%t)",
req.ptr.ID, req.action.Sync())
}
}()
if req.action.Sync() {
// If the sync cache is close to full, reschedule the prefetch.
p.reschedulePrefetch(req)
p.sendOverallSyncStatusNotification()
return true, false
}
// Otherwise, only stop if we're supposed to stop when full.
doStop = req.action.StopIfFull()
if doStop {
doCancel = true
}
return doStop, doCancel
}
type prefetchStatusRequest struct {
ptr data.BlockPointer
ch chan<- PrefetchProgress
}
func (p *blockPrefetcher) handlePrefetchRequest(req *prefetchRequest) {
pre, isPrefetchWaiting := p.prefetches[req.ptr.ID]
if isPrefetchWaiting && pre.req == nil {
// If this prefetch already appeared in the tree, ensure it
// has a req associated with it.
pre.req = req
}
p.clearRescheduleState(req.ptr.ID)
// If this request is just asking for the wait channel,
// send it now. (This is processed in the same queue as
// the prefetch requests, to guarantee an initial prefetch
// request has always been processed before the wait
// channel request is processed.)
if req.sendCh != nil {
if !isPrefetchWaiting {
req.sendCh <- p.closedCh