VictoriaMetrics/lib/mergeset/table.go
Nikolay dd7ebd6779
lib/storage: creates parts.json on start-up if it not exists. (#4450)
* lib/storage: creates parts.json on start-up if it not exists.
It fixes migrations from versions below v1.90.0.
Previously parts.json was created only after successful merge.
But if merge was interruped for some reason (OOM or shutdown), parts.json wasn't created and partitions left after interruped merge weren't properly deleted.
Since VM cannot check if it must be removed or not.
https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4336

* Apply suggestions from code review

Co-authored-by: Roman Khavronenko <roman@victoriametrics.com>

* Update lib/storage/partition.go

Co-authored-by: Roman Khavronenko <roman@victoriametrics.com>

---------

Co-authored-by: Roman Khavronenko <roman@victoriametrics.com>
2023-07-06 17:10:26 -07:00

1645 lines
43 KiB
Go

package mergeset
import (
"encoding/json"
"errors"
"fmt"
"os"
"path/filepath"
"sort"
"strings"
"sync"
"sync/atomic"
"time"
"unsafe"
"github.com/VictoriaMetrics/VictoriaMetrics/lib/cgroup"
"github.com/VictoriaMetrics/VictoriaMetrics/lib/fasttime"
"github.com/VictoriaMetrics/VictoriaMetrics/lib/fs"
"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
"github.com/VictoriaMetrics/VictoriaMetrics/lib/memory"
"github.com/VictoriaMetrics/VictoriaMetrics/lib/syncwg"
)
// maxInmemoryParts is the maximum number of inmemory parts in the table.
//
// This number may be reached when the insertion pace outreaches merger pace.
// If this number is reached, then assisted merges are performed
// during data ingestion.
const maxInmemoryParts = 30
// maxFileParts is the maximum number of file parts in the table.
//
// This number may be reached when the insertion pace outreaches merger pace.
// If this number is reached, then assisted merges are performed
// during data ingestion.
const maxFileParts = 64
// Default number of parts to merge at once.
//
// This number has been obtained empirically - it gives the lowest possible overhead.
// See appendPartsToMerge tests for details.
const defaultPartsToMerge = 15
// The final number of parts to merge at once.
//
// It must be smaller than defaultPartsToMerge.
// Lower value improves select performance at the cost of increased
// write amplification.
const finalPartsToMerge = 2
// maxPartSize is the maximum part size in bytes.
//
// This number should be limited by the amount of time required to merge parts of this summary size.
// The required time shouldn't exceed a day.
const maxPartSize = 400e9
// The interval for flushing buffered data to parts, so it becomes visible to search.
const pendingItemsFlushInterval = time.Second
// The interval for guaranteed flush of recently ingested data from memory to on-disk parts,
// so they survive process crash.
var dataFlushInterval = 5 * time.Second
// SetDataFlushInterval sets the interval for guaranteed flush of recently ingested data from memory to disk.
//
// The data can be flushed from memory to disk more frequently if it doesn't fit the memory limit.
//
// This function must be called before initializing the indexdb.
func SetDataFlushInterval(d time.Duration) {
if d > pendingItemsFlushInterval {
dataFlushInterval = d
}
}
// maxItemsPerCachedPart is the maximum items per created part by the merge,
// which must be cached in the OS page cache.
//
// Such parts are usually frequently accessed, so it is good to cache their
// contents in OS page cache.
func maxItemsPerCachedPart() uint64 {
mem := memory.Remaining()
// Production data shows that each item occupies ~4 bytes in the compressed part.
// It is expected no more than defaultPartsToMerge/2 parts exist
// in the OS page cache before they are merged into bigger part.
// Halft of the remaining RAM must be left for lib/storage parts,
// so the maxItems is calculated using the below code:
maxItems := uint64(mem) / (4 * defaultPartsToMerge)
if maxItems < 1e6 {
maxItems = 1e6
}
return maxItems
}
// Table represents mergeset table.
type Table struct {
// Atomically updated counters must go first in the struct, so they are properly
// aligned to 8 bytes on 32-bit architectures.
// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/212
activeInmemoryMerges uint64
activeFileMerges uint64
inmemoryMergesCount uint64
fileMergesCount uint64
inmemoryItemsMerged uint64
fileItemsMerged uint64
inmemoryAssistedMerges uint64
fileAssistedMerges uint64
itemsAdded uint64
itemsAddedSizeBytes uint64
mergeIdx uint64
path string
flushCallback func()
flushCallbackWorkerWG sync.WaitGroup
needFlushCallbackCall uint32
prepareBlock PrepareBlockCallback
isReadOnly *uint32
// rawItems contains recently added items that haven't been converted to parts yet.
//
// rawItems aren't used in search for performance reasons
rawItems rawItemsShards
// partsLock protects inmemoryParts and fileParts.
partsLock sync.Mutex
// inmemoryParts contains inmemory parts.
inmemoryParts []*partWrapper
// fileParts contains file-backed parts.
fileParts []*partWrapper
// This channel is used for signaling the background mergers that there are parts,
// which may need to be merged.
needMergeCh chan struct{}
flockF *os.File
stopCh chan struct{}
wg sync.WaitGroup
// Use syncwg instead of sync, since Add/Wait may be called from concurrent goroutines.
rawItemsPendingFlushesWG syncwg.WaitGroup
}
type rawItemsShards struct {
shardIdx uint32
// shards reduce lock contention when adding rows on multi-CPU systems.
shards []rawItemsShard
}
// The number of shards for rawItems per table.
//
// Higher number of shards reduces CPU contention and increases the max bandwidth on multi-core systems.
var rawItemsShardsPerTable = func() int {
cpus := cgroup.AvailableCPUs()
multiplier := cpus
if multiplier > 16 {
multiplier = 16
}
return (cpus*multiplier + 1) / 2
}()
const maxBlocksPerShard = 256
func (riss *rawItemsShards) init() {
riss.shards = make([]rawItemsShard, rawItemsShardsPerTable)
}
func (riss *rawItemsShards) addItems(tb *Table, items [][]byte) {
shards := riss.shards
shardsLen := uint32(len(shards))
for len(items) > 0 {
n := atomic.AddUint32(&riss.shardIdx, 1)
idx := n % shardsLen
items = shards[idx].addItems(tb, items)
}
}
func (riss *rawItemsShards) Len() int {
n := 0
for i := range riss.shards {
n += riss.shards[i].Len()
}
return n
}
type rawItemsShardNopad struct {
// Put lastFlushTime to the top in order to avoid unaligned memory access on 32-bit architectures
lastFlushTime uint64
mu sync.Mutex
ibs []*inmemoryBlock
}
type rawItemsShard struct {
rawItemsShardNopad
// The padding prevents false sharing on widespread platforms with
// 128 mod (cache line size) = 0 .
_ [128 - unsafe.Sizeof(rawItemsShardNopad{})%128]byte
}
func (ris *rawItemsShard) Len() int {
ris.mu.Lock()
n := 0
for _, ib := range ris.ibs {
n += len(ib.items)
}
ris.mu.Unlock()
return n
}
func (ris *rawItemsShard) addItems(tb *Table, items [][]byte) [][]byte {
var ibsToFlush []*inmemoryBlock
var tailItems [][]byte
ris.mu.Lock()
ibs := ris.ibs
if len(ibs) == 0 {
ib := getInmemoryBlock()
ibs = append(ibs, ib)
ris.ibs = ibs
}
ib := ibs[len(ibs)-1]
for i, item := range items {
if ib.Add(item) {
continue
}
if len(ibs) >= maxBlocksPerShard {
ibsToFlush = ibs
ibs = make([]*inmemoryBlock, 0, maxBlocksPerShard)
tailItems = items[i:]
atomic.StoreUint64(&ris.lastFlushTime, fasttime.UnixTimestamp())
break
}
ib = getInmemoryBlock()
if ib.Add(item) {
ibs = append(ibs, ib)
continue
}
putInmemoryBlock(ib)
logger.Panicf("BUG: cannot insert too big item into an empty inmemoryBlock len(item)=%d; the caller should be responsible for avoiding too big items", len(item))
}
ris.ibs = ibs
ris.mu.Unlock()
tb.flushBlocksToParts(ibsToFlush, false)
if len(ibsToFlush) > 0 {
// Run assisted merges if needed.
flushConcurrencyCh <- struct{}{}
tb.assistedMergeForInmemoryParts()
tb.assistedMergeForFileParts()
<-flushConcurrencyCh
}
return tailItems
}
type partWrapper struct {
p *part
mp *inmemoryPart
refCount uint32
// mustBeDeleted marks partWrapper for deletion.
// This field should be updated only after partWrapper
// was removed from the list of active parts.
mustBeDeleted uint32
isInMerge bool
// The deadline when the in-memory part must be flushed to disk.
flushToDiskDeadline time.Time
}
func (pw *partWrapper) incRef() {
atomic.AddUint32(&pw.refCount, 1)
}
func (pw *partWrapper) decRef() {
n := atomic.AddUint32(&pw.refCount, ^uint32(0))
if int32(n) < 0 {
logger.Panicf("BUG: pw.refCount must be bigger than 0; got %d", int32(n))
}
if n > 0 {
return
}
deletePath := ""
if pw.mp == nil && atomic.LoadUint32(&pw.mustBeDeleted) != 0 {
deletePath = pw.p.path
}
if pw.mp != nil {
// Do not return pw.mp to pool via putInmemoryPart(),
// since pw.mp size may be too big compared to other entries stored in the pool.
// This may result in increased memory usage because of high fragmentation.
pw.mp = nil
}
pw.p.MustClose()
pw.p = nil
if deletePath != "" {
fs.MustRemoveAll(deletePath)
}
}
// MustOpenTable opens a table on the given path.
//
// Optional flushCallback is called every time new data batch is flushed
// to the underlying storage and becomes visible to search.
//
// Optional prepareBlock is called during merge before flushing the prepared block
// to persistent storage.
//
// The table is created if it doesn't exist yet.
func MustOpenTable(path string, flushCallback func(), prepareBlock PrepareBlockCallback, isReadOnly *uint32) *Table {
path = filepath.Clean(path)
// Create a directory for the table if it doesn't exist yet.
fs.MustMkdirIfNotExist(path)
// Protect from concurrent opens.
flockF := fs.MustCreateFlockFile(path)
// Open table parts.
pws := mustOpenParts(path)
tb := &Table{
path: path,
flushCallback: flushCallback,
prepareBlock: prepareBlock,
isReadOnly: isReadOnly,
fileParts: pws,
mergeIdx: uint64(time.Now().UnixNano()),
needMergeCh: make(chan struct{}, 1),
flockF: flockF,
stopCh: make(chan struct{}),
}
tb.rawItems.init()
tb.startBackgroundWorkers()
// Wake up a single background merger, so it could start merging parts if needed.
tb.notifyBackgroundMergers()
if flushCallback != nil {
tb.flushCallbackWorkerWG.Add(1)
go func() {
// call flushCallback once per 10 seconds in order to improve the effectiveness of caches,
// which are reset by the flushCallback.
tc := time.NewTicker(10 * time.Second)
for {
select {
case <-tb.stopCh:
tb.flushCallback()
tb.flushCallbackWorkerWG.Done()
return
case <-tc.C:
if atomic.CompareAndSwapUint32(&tb.needFlushCallbackCall, 1, 0) {
tb.flushCallback()
}
}
}
}()
}
return tb
}
func (tb *Table) startBackgroundWorkers() {
tb.startMergeWorkers()
tb.startInmemoryPartsFlusher()
tb.startPendingItemsFlusher()
}
// MustClose closes the table.
func (tb *Table) MustClose() {
close(tb.stopCh)
// Waiting for background workers to stop
tb.wg.Wait()
tb.flushInmemoryItems()
tb.flushCallbackWorkerWG.Wait()
// Remove references to parts from the tb, so they may be eventually closed after all the searches are done.
tb.partsLock.Lock()
inmemoryParts := tb.inmemoryParts
fileParts := tb.fileParts
tb.inmemoryParts = nil
tb.fileParts = nil
tb.partsLock.Unlock()
for _, pw := range inmemoryParts {
pw.decRef()
}
for _, pw := range fileParts {
pw.decRef()
}
// Release flockF
fs.MustClose(tb.flockF)
tb.flockF = nil
}
// Path returns the path to tb on the filesystem.
func (tb *Table) Path() string {
return tb.path
}
// TableMetrics contains essential metrics for the Table.
type TableMetrics struct {
ActiveInmemoryMerges uint64
ActiveFileMerges uint64
InmemoryMergesCount uint64
FileMergesCount uint64
InmemoryItemsMerged uint64
FileItemsMerged uint64
InmemoryAssistedMerges uint64
FileAssistedMerges uint64
ItemsAdded uint64
ItemsAddedSizeBytes uint64
PendingItems uint64
InmemoryPartsCount uint64
FilePartsCount uint64
InmemoryBlocksCount uint64
FileBlocksCount uint64
InmemoryItemsCount uint64
FileItemsCount uint64
InmemorySizeBytes uint64
FileSizeBytes uint64
DataBlocksCacheSize uint64
DataBlocksCacheSizeBytes uint64
DataBlocksCacheSizeMaxBytes uint64
DataBlocksCacheRequests uint64
DataBlocksCacheMisses uint64
IndexBlocksCacheSize uint64
IndexBlocksCacheSizeBytes uint64
IndexBlocksCacheSizeMaxBytes uint64
IndexBlocksCacheRequests uint64
IndexBlocksCacheMisses uint64
PartsRefCount uint64
}
// TotalItemsCount returns the total number of items in the table.
func (tm *TableMetrics) TotalItemsCount() uint64 {
return tm.InmemoryItemsCount + tm.FileItemsCount
}
// UpdateMetrics updates m with metrics from tb.
func (tb *Table) UpdateMetrics(m *TableMetrics) {
m.ActiveInmemoryMerges += atomic.LoadUint64(&tb.activeInmemoryMerges)
m.ActiveFileMerges += atomic.LoadUint64(&tb.activeFileMerges)
m.InmemoryMergesCount += atomic.LoadUint64(&tb.inmemoryMergesCount)
m.FileMergesCount += atomic.LoadUint64(&tb.fileMergesCount)
m.InmemoryItemsMerged += atomic.LoadUint64(&tb.inmemoryItemsMerged)
m.FileItemsMerged += atomic.LoadUint64(&tb.fileItemsMerged)
m.InmemoryAssistedMerges += atomic.LoadUint64(&tb.inmemoryAssistedMerges)
m.FileAssistedMerges += atomic.LoadUint64(&tb.fileAssistedMerges)
m.ItemsAdded += atomic.LoadUint64(&tb.itemsAdded)
m.ItemsAddedSizeBytes += atomic.LoadUint64(&tb.itemsAddedSizeBytes)
m.PendingItems += uint64(tb.rawItems.Len())
tb.partsLock.Lock()
m.InmemoryPartsCount += uint64(len(tb.inmemoryParts))
for _, pw := range tb.inmemoryParts {
p := pw.p
m.InmemoryBlocksCount += p.ph.blocksCount
m.InmemoryItemsCount += p.ph.itemsCount
m.InmemorySizeBytes += p.size
m.PartsRefCount += uint64(atomic.LoadUint32(&pw.refCount))
}
m.FilePartsCount += uint64(len(tb.fileParts))
for _, pw := range tb.fileParts {
p := pw.p
m.FileBlocksCount += p.ph.blocksCount
m.FileItemsCount += p.ph.itemsCount
m.FileSizeBytes += p.size
m.PartsRefCount += uint64(atomic.LoadUint32(&pw.refCount))
}
tb.partsLock.Unlock()
m.DataBlocksCacheSize = uint64(ibCache.Len())
m.DataBlocksCacheSizeBytes = uint64(ibCache.SizeBytes())
m.DataBlocksCacheSizeMaxBytes = uint64(ibCache.SizeMaxBytes())
m.DataBlocksCacheRequests = ibCache.Requests()
m.DataBlocksCacheMisses = ibCache.Misses()
m.IndexBlocksCacheSize = uint64(idxbCache.Len())
m.IndexBlocksCacheSizeBytes = uint64(idxbCache.SizeBytes())
m.IndexBlocksCacheSizeMaxBytes = uint64(idxbCache.SizeMaxBytes())
m.IndexBlocksCacheRequests = idxbCache.Requests()
m.IndexBlocksCacheMisses = idxbCache.Misses()
}
// AddItems adds the given items to the tb.
//
// The function panics when items contains an item with length exceeding maxInmemoryBlockSize.
// It is caller's responsibility to make sure there are no too long items.
func (tb *Table) AddItems(items [][]byte) {
tb.rawItems.addItems(tb, items)
atomic.AddUint64(&tb.itemsAdded, uint64(len(items)))
n := 0
for _, item := range items {
n += len(item)
}
atomic.AddUint64(&tb.itemsAddedSizeBytes, uint64(n))
}
// getParts appends parts snapshot to dst and returns it.
//
// The appended parts must be released with putParts.
func (tb *Table) getParts(dst []*partWrapper) []*partWrapper {
tb.partsLock.Lock()
for _, pw := range tb.inmemoryParts {
pw.incRef()
}
for _, pw := range tb.fileParts {
pw.incRef()
}
dst = append(dst, tb.inmemoryParts...)
dst = append(dst, tb.fileParts...)
tb.partsLock.Unlock()
return dst
}
// putParts releases the given pws obtained via getParts.
func (tb *Table) putParts(pws []*partWrapper) {
for _, pw := range pws {
pw.decRef()
}
}
func (tb *Table) mergePartsOptimal(pws []*partWrapper) error {
sortPartsForOptimalMerge(pws)
for len(pws) > 0 {
n := defaultPartsToMerge
if n > len(pws) {
n = len(pws)
}
pwsChunk := pws[:n]
pws = pws[n:]
err := tb.mergeParts(pwsChunk, nil, true)
if err == nil {
continue
}
tb.releasePartsToMerge(pws)
return fmt.Errorf("cannot optimally merge %d parts: %w", n, err)
}
return nil
}
// DebugFlush makes sure all the recently added data is visible to search.
//
// Note: this function doesn't store all the in-memory data to disk - it just converts
// recently added items to searchable parts, which can be stored either in memory
// (if they are quite small) or to persistent disk.
//
// This function is for debugging and testing purposes only,
// since it may slow down data ingestion when used frequently.
func (tb *Table) DebugFlush() {
tb.flushPendingItems(nil, true)
// Wait for background flushers to finish.
tb.rawItemsPendingFlushesWG.Wait()
}
func (tb *Table) startInmemoryPartsFlusher() {
tb.wg.Add(1)
go func() {
tb.inmemoryPartsFlusher()
tb.wg.Done()
}()
}
func (tb *Table) startPendingItemsFlusher() {
tb.wg.Add(1)
go func() {
tb.pendingItemsFlusher()
tb.wg.Done()
}()
}
func (tb *Table) inmemoryPartsFlusher() {
ticker := time.NewTicker(dataFlushInterval)
defer ticker.Stop()
for {
select {
case <-tb.stopCh:
return
case <-ticker.C:
tb.flushInmemoryParts(false)
}
}
}
func (tb *Table) pendingItemsFlusher() {
ticker := time.NewTicker(pendingItemsFlushInterval)
defer ticker.Stop()
var ibs []*inmemoryBlock
for {
select {
case <-tb.stopCh:
return
case <-ticker.C:
ibs = tb.flushPendingItems(ibs[:0], false)
for i := range ibs {
ibs[i] = nil
}
}
}
}
func (tb *Table) flushPendingItems(dst []*inmemoryBlock, isFinal bool) []*inmemoryBlock {
return tb.rawItems.flush(tb, dst, isFinal)
}
func (tb *Table) flushInmemoryItems() {
tb.rawItems.flush(tb, nil, true)
tb.flushInmemoryParts(true)
}
func (tb *Table) flushInmemoryParts(isFinal bool) {
currentTime := time.Now()
var pws []*partWrapper
tb.partsLock.Lock()
for _, pw := range tb.inmemoryParts {
if !pw.isInMerge && (isFinal || pw.flushToDiskDeadline.Before(currentTime)) {
pw.isInMerge = true
pws = append(pws, pw)
}
}
tb.partsLock.Unlock()
if err := tb.mergePartsOptimal(pws); err != nil {
logger.Panicf("FATAL: cannot merge in-memory parts: %s", err)
}
}
func (riss *rawItemsShards) flush(tb *Table, dst []*inmemoryBlock, isFinal bool) []*inmemoryBlock {
tb.rawItemsPendingFlushesWG.Add(1)
defer tb.rawItemsPendingFlushesWG.Done()
for i := range riss.shards {
dst = riss.shards[i].appendBlocksToFlush(dst, tb, isFinal)
}
tb.flushBlocksToParts(dst, isFinal)
return dst
}
func (ris *rawItemsShard) appendBlocksToFlush(dst []*inmemoryBlock, tb *Table, isFinal bool) []*inmemoryBlock {
currentTime := fasttime.UnixTimestamp()
flushSeconds := int64(pendingItemsFlushInterval.Seconds())
if flushSeconds <= 0 {
flushSeconds = 1
}
lastFlushTime := atomic.LoadUint64(&ris.lastFlushTime)
if !isFinal && currentTime < lastFlushTime+uint64(flushSeconds) {
// Fast path - nothing to flush
return dst
}
// Slow path - move ris.ibs to dst
ris.mu.Lock()
ibs := ris.ibs
dst = append(dst, ibs...)
for i := range ibs {
ibs[i] = nil
}
ris.ibs = ibs[:0]
atomic.StoreUint64(&ris.lastFlushTime, currentTime)
ris.mu.Unlock()
return dst
}
func (tb *Table) flushBlocksToParts(ibs []*inmemoryBlock, isFinal bool) {
if len(ibs) == 0 {
return
}
var pwsLock sync.Mutex
pws := make([]*partWrapper, 0, (len(ibs)+defaultPartsToMerge-1)/defaultPartsToMerge)
wg := getWaitGroup()
for len(ibs) > 0 {
n := defaultPartsToMerge
if n > len(ibs) {
n = len(ibs)
}
wg.Add(1)
flushConcurrencyCh <- struct{}{}
go func(ibsChunk []*inmemoryBlock) {
defer func() {
<-flushConcurrencyCh
wg.Done()
}()
pw := tb.createInmemoryPart(ibsChunk)
if pw == nil {
return
}
pwsLock.Lock()
pws = append(pws, pw)
pwsLock.Unlock()
}(ibs[:n])
ibs = ibs[n:]
}
wg.Wait()
putWaitGroup(wg)
tb.partsLock.Lock()
tb.inmemoryParts = append(tb.inmemoryParts, pws...)
for range pws {
if !tb.notifyBackgroundMergers() {
break
}
}
tb.partsLock.Unlock()
if tb.flushCallback != nil {
if isFinal {
tb.flushCallback()
} else {
atomic.CompareAndSwapUint32(&tb.needFlushCallbackCall, 0, 1)
}
}
}
func (tb *Table) notifyBackgroundMergers() bool {
select {
case tb.needMergeCh <- struct{}{}:
return true
default:
return false
}
}
var flushConcurrencyLimit = func() int {
n := cgroup.AvailableCPUs()
if n < 2 {
// Allow at least 2 concurrent flushers on systems with a single CPU core
// in order to guarantee that in-memory data flushes and background merges can be continued
// when a single flusher is busy with the long merge.
n = 2
}
return n
}()
var flushConcurrencyCh = make(chan struct{}, flushConcurrencyLimit)
func needAssistedMerge(pws []*partWrapper, maxParts int) bool {
if len(pws) < maxParts {
return false
}
return getNotInMergePartsCount(pws) >= defaultPartsToMerge
}
func (tb *Table) assistedMergeForInmemoryParts() {
for {
tb.partsLock.Lock()
needMerge := needAssistedMerge(tb.inmemoryParts, maxInmemoryParts)
tb.partsLock.Unlock()
if !needMerge {
return
}
atomic.AddUint64(&tb.inmemoryAssistedMerges, 1)
err := tb.mergeInmemoryParts()
if err == nil {
continue
}
if errors.Is(err, errNothingToMerge) || errors.Is(err, errForciblyStopped) {
return
}
logger.Panicf("FATAL: cannot assist with merging inmemory parts: %s", err)
}
}
func (tb *Table) assistedMergeForFileParts() {
for {
tb.partsLock.Lock()
needMerge := needAssistedMerge(tb.fileParts, maxFileParts)
tb.partsLock.Unlock()
if !needMerge {
return
}
atomic.AddUint64(&tb.fileAssistedMerges, 1)
err := tb.mergeExistingParts(false)
if err == nil {
continue
}
if errors.Is(err, errNothingToMerge) || errors.Is(err, errForciblyStopped) || errors.Is(err, errReadOnlyMode) {
return
}
logger.Panicf("FATAL: cannot assist with merging file parts: %s", err)
}
}
func getNotInMergePartsCount(pws []*partWrapper) int {
n := 0
for _, pw := range pws {
if !pw.isInMerge {
n++
}
}
return n
}
func getWaitGroup() *sync.WaitGroup {
v := wgPool.Get()
if v == nil {
return &sync.WaitGroup{}
}
return v.(*sync.WaitGroup)
}
func putWaitGroup(wg *sync.WaitGroup) {
wgPool.Put(wg)
}
var wgPool sync.Pool
func (tb *Table) createInmemoryPart(ibs []*inmemoryBlock) *partWrapper {
outItemsCount := uint64(0)
for _, ib := range ibs {
outItemsCount += uint64(ib.Len())
}
// Prepare blockStreamReaders for source blocks.
bsrs := make([]*blockStreamReader, 0, len(ibs))
for _, ib := range ibs {
if len(ib.items) == 0 {
continue
}
bsr := getBlockStreamReader()
bsr.MustInitFromInmemoryBlock(ib)
putInmemoryBlock(ib)
bsrs = append(bsrs, bsr)
}
if len(bsrs) == 0 {
return nil
}
flushToDiskDeadline := time.Now().Add(dataFlushInterval)
if len(bsrs) == 1 {
// Nothing to merge. Just return a single inmemory part.
bsr := bsrs[0]
mp := &inmemoryPart{}
mp.Init(&bsr.Block)
putBlockStreamReader(bsr)
return newPartWrapperFromInmemoryPart(mp, flushToDiskDeadline)
}
// Prepare blockStreamWriter for destination part.
compressLevel := getCompressLevel(outItemsCount)
bsw := getBlockStreamWriter()
mpDst := &inmemoryPart{}
bsw.MustInitFromInmemoryPart(mpDst, compressLevel)
// Merge parts.
// The merge shouldn't be interrupted by stopCh,
// since it may be final after stopCh is closed.
atomic.AddUint64(&tb.activeInmemoryMerges, 1)
err := mergeBlockStreams(&mpDst.ph, bsw, bsrs, tb.prepareBlock, nil, &tb.inmemoryItemsMerged)
atomic.AddUint64(&tb.activeInmemoryMerges, ^uint64(0))
atomic.AddUint64(&tb.inmemoryMergesCount, 1)
if err != nil {
logger.Panicf("FATAL: cannot merge inmemoryBlocks: %s", err)
}
putBlockStreamWriter(bsw)
for _, bsr := range bsrs {
putBlockStreamReader(bsr)
}
return newPartWrapperFromInmemoryPart(mpDst, flushToDiskDeadline)
}
func newPartWrapperFromInmemoryPart(mp *inmemoryPart, flushToDiskDeadline time.Time) *partWrapper {
p := mp.NewPart()
return &partWrapper{
p: p,
mp: mp,
refCount: 1,
flushToDiskDeadline: flushToDiskDeadline,
}
}
func (tb *Table) startMergeWorkers() {
// The actual number of concurrent merges is limited inside mergeWorker() below.
for i := 0; i < cap(mergeWorkersLimitCh); i++ {
tb.wg.Add(1)
go func() {
tb.mergeWorker()
tb.wg.Done()
}()
}
}
func getMaxInmemoryPartSize() uint64 {
// Allow up to 5% of memory for in-memory parts.
n := uint64(0.05 * float64(memory.Allowed()) / maxInmemoryParts)
if n < 1e6 {
n = 1e6
}
return n
}
func (tb *Table) getMaxFilePartSize() uint64 {
n := fs.MustGetFreeSpace(tb.path)
// Divide free space by the max number of concurrent merges.
maxOutBytes := n / uint64(cap(mergeWorkersLimitCh))
if maxOutBytes > maxPartSize {
maxOutBytes = maxPartSize
}
return maxOutBytes
}
func (tb *Table) canBackgroundMerge() bool {
return atomic.LoadUint32(tb.isReadOnly) == 0
}
var errReadOnlyMode = fmt.Errorf("storage is in readonly mode")
func (tb *Table) mergeInmemoryParts() error {
maxOutBytes := tb.getMaxFilePartSize()
tb.partsLock.Lock()
pws := getPartsToMerge(tb.inmemoryParts, maxOutBytes, false)
tb.partsLock.Unlock()
return tb.mergeParts(pws, tb.stopCh, false)
}
func (tb *Table) mergeExistingParts(isFinal bool) error {
if !tb.canBackgroundMerge() {
// Do not perform background merge in read-only mode
// in order to prevent from disk space shortage.
// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2603
return errReadOnlyMode
}
maxOutBytes := tb.getMaxFilePartSize()
tb.partsLock.Lock()
dst := make([]*partWrapper, 0, len(tb.inmemoryParts)+len(tb.fileParts))
dst = append(dst, tb.inmemoryParts...)
dst = append(dst, tb.fileParts...)
pws := getPartsToMerge(dst, maxOutBytes, isFinal)
tb.partsLock.Unlock()
return tb.mergeParts(pws, tb.stopCh, isFinal)
}
func (tb *Table) mergeWorker() {
var lastMergeTime uint64
isFinal := false
for {
// Limit the number of concurrent calls to mergeExistingParts, since the total number of merge workers
// across tables may exceed the the cap(mergeWorkersLimitCh).
mergeWorkersLimitCh <- struct{}{}
err := tb.mergeExistingParts(isFinal)
<-mergeWorkersLimitCh
if err == nil {
// Try merging additional parts.
lastMergeTime = fasttime.UnixTimestamp()
isFinal = false
continue
}
if errors.Is(err, errForciblyStopped) {
// The merger has been stopped.
return
}
if !errors.Is(err, errNothingToMerge) && !errors.Is(err, errReadOnlyMode) {
// Unexpected error.
logger.Panicf("FATAL: unrecoverable error when merging inmemory parts in %q: %s", tb.path, err)
}
if finalMergeDelaySeconds > 0 && fasttime.UnixTimestamp()-lastMergeTime > finalMergeDelaySeconds {
// We have free time for merging into bigger parts.
// This should improve select performance.
lastMergeTime = fasttime.UnixTimestamp()
isFinal = true
continue
}
// Nothing to merge. Wait for the notification of new merge.
select {
case <-tb.stopCh:
return
case <-tb.needMergeCh:
}
}
}
// Disable final merge by default, since it may lead to high disk IO and CPU usage
// after some inactivity time.
var finalMergeDelaySeconds = uint64(0)
// SetFinalMergeDelay sets the delay before doing final merge for Table without newly ingested data.
//
// This function may be called only before Table initialization.
func SetFinalMergeDelay(delay time.Duration) {
if delay <= 0 {
return
}
finalMergeDelaySeconds = uint64(delay.Seconds() + 1)
}
var errNothingToMerge = fmt.Errorf("nothing to merge")
func (tb *Table) releasePartsToMerge(pws []*partWrapper) {
tb.partsLock.Lock()
for _, pw := range pws {
if !pw.isInMerge {
logger.Panicf("BUG: missing isInMerge flag on the part %q", pw.p.path)
}
pw.isInMerge = false
}
tb.partsLock.Unlock()
}
// mergeParts merges pws to a single resulting part.
//
// Merging is immediately stopped if stopCh is closed.
//
// If isFinal is set, then the resulting part will be stored to disk.
//
// All the parts inside pws must have isInMerge field set to true.
func (tb *Table) mergeParts(pws []*partWrapper, stopCh <-chan struct{}, isFinal bool) error {
if len(pws) == 0 {
// Nothing to merge.
return errNothingToMerge
}
startTime := time.Now()
// Initialize destination paths.
dstPartType := getDstPartType(pws, isFinal)
mergeIdx := tb.nextMergeIdx()
dstPartPath := ""
if dstPartType == partFile {
dstPartPath = filepath.Join(tb.path, fmt.Sprintf("%016X", mergeIdx))
}
if isFinal && len(pws) == 1 && pws[0].mp != nil {
// Fast path: flush a single in-memory part to disk.
mp := pws[0].mp
mp.MustStoreToDisk(dstPartPath)
pwNew := tb.openCreatedPart(pws, nil, dstPartPath)
tb.swapSrcWithDstParts(pws, pwNew, dstPartType)
return nil
}
// Prepare BlockStreamReaders for source parts.
bsrs := mustOpenBlockStreamReaders(pws)
// Prepare BlockStreamWriter for destination part.
srcSize := uint64(0)
srcItemsCount := uint64(0)
srcBlocksCount := uint64(0)
for _, pw := range pws {
srcSize += pw.p.size
srcItemsCount += pw.p.ph.itemsCount
srcBlocksCount += pw.p.ph.blocksCount
}
compressLevel := getCompressLevel(srcItemsCount)
bsw := getBlockStreamWriter()
var mpNew *inmemoryPart
if dstPartType == partInmemory {
mpNew = &inmemoryPart{}
bsw.MustInitFromInmemoryPart(mpNew, compressLevel)
} else {
nocache := srcItemsCount > maxItemsPerCachedPart()
bsw.MustInitFromFilePart(dstPartPath, nocache, compressLevel)
}
// Merge source parts to destination part.
ph, err := tb.mergePartsInternal(dstPartPath, bsw, bsrs, dstPartType, stopCh)
putBlockStreamWriter(bsw)
for _, bsr := range bsrs {
putBlockStreamReader(bsr)
}
if err != nil {
tb.releasePartsToMerge(pws)
return err
}
if mpNew != nil {
// Update partHeader for destination inmemory part after the merge.
mpNew.ph = *ph
} else {
// Make sure the created part directory listing is synced.
fs.MustSyncPath(dstPartPath)
}
// Atomically swap the source parts with the newly created part.
pwNew := tb.openCreatedPart(pws, mpNew, dstPartPath)
pDst := pwNew.p
dstItemsCount := pDst.ph.itemsCount
dstBlocksCount := pDst.ph.blocksCount
dstSize := pDst.size
tb.swapSrcWithDstParts(pws, pwNew, dstPartType)
d := time.Since(startTime)
if d <= 30*time.Second {
return nil
}
// Log stats for long merges.
durationSecs := d.Seconds()
itemsPerSec := int(float64(srcItemsCount) / durationSecs)
logger.Infof("merged (%d parts, %d items, %d blocks, %d bytes) into (1 part, %d items, %d blocks, %d bytes) in %.3f seconds at %d items/sec to %q",
len(pws), srcItemsCount, srcBlocksCount, srcSize, dstItemsCount, dstBlocksCount, dstSize, durationSecs, itemsPerSec, dstPartPath)
return nil
}
func getFlushToDiskDeadline(pws []*partWrapper) time.Time {
d := time.Now().Add(dataFlushInterval)
for _, pw := range pws {
if pw.mp != nil && pw.flushToDiskDeadline.Before(d) {
d = pw.flushToDiskDeadline
}
}
return d
}
type partType int
var (
partInmemory = partType(0)
partFile = partType(1)
)
func getDstPartType(pws []*partWrapper, isFinal bool) partType {
dstPartSize := getPartsSize(pws)
if isFinal || dstPartSize > getMaxInmemoryPartSize() {
return partFile
}
if !areAllInmemoryParts(pws) {
// If at least a single source part is located in file,
// then the destination part must be in file for durability reasons.
return partFile
}
return partInmemory
}
func mustOpenBlockStreamReaders(pws []*partWrapper) []*blockStreamReader {
bsrs := make([]*blockStreamReader, 0, len(pws))
for _, pw := range pws {
bsr := getBlockStreamReader()
if pw.mp != nil {
bsr.MustInitFromInmemoryPart(pw.mp)
} else {
bsr.MustInitFromFilePart(pw.p.path)
}
bsrs = append(bsrs, bsr)
}
return bsrs
}
func (tb *Table) mergePartsInternal(dstPartPath string, bsw *blockStreamWriter, bsrs []*blockStreamReader, dstPartType partType, stopCh <-chan struct{}) (*partHeader, error) {
var ph partHeader
var itemsMerged *uint64
var mergesCount *uint64
var activeMerges *uint64
switch dstPartType {
case partInmemory:
itemsMerged = &tb.inmemoryItemsMerged
mergesCount = &tb.inmemoryMergesCount
activeMerges = &tb.activeInmemoryMerges
case partFile:
itemsMerged = &tb.fileItemsMerged
mergesCount = &tb.fileMergesCount
activeMerges = &tb.activeFileMerges
default:
logger.Panicf("BUG: unknown partType=%d", dstPartType)
}
atomic.AddUint64(activeMerges, 1)
err := mergeBlockStreams(&ph, bsw, bsrs, tb.prepareBlock, stopCh, itemsMerged)
atomic.AddUint64(activeMerges, ^uint64(0))
atomic.AddUint64(mergesCount, 1)
if err != nil {
return nil, fmt.Errorf("cannot merge %d parts to %s: %w", len(bsrs), dstPartPath, err)
}
if dstPartPath != "" {
ph.MustWriteMetadata(dstPartPath)
}
return &ph, nil
}
func (tb *Table) openCreatedPart(pws []*partWrapper, mpNew *inmemoryPart, dstPartPath string) *partWrapper {
// Open the created part.
if mpNew != nil {
// Open the created part from memory.
flushToDiskDeadline := getFlushToDiskDeadline(pws)
pwNew := newPartWrapperFromInmemoryPart(mpNew, flushToDiskDeadline)
return pwNew
}
// Open the created part from disk.
pNew := mustOpenFilePart(dstPartPath)
pwNew := &partWrapper{
p: pNew,
refCount: 1,
}
return pwNew
}
func areAllInmemoryParts(pws []*partWrapper) bool {
for _, pw := range pws {
if pw.mp == nil {
return false
}
}
return true
}
func (tb *Table) swapSrcWithDstParts(pws []*partWrapper, pwNew *partWrapper, dstPartType partType) {
// Atomically unregister old parts and add new part to tb.
m := make(map[*partWrapper]bool, len(pws))
for _, pw := range pws {
m[pw] = true
}
if len(m) != len(pws) {
logger.Panicf("BUG: %d duplicate parts found when merging %d parts", len(pws)-len(m), len(pws))
}
removedInmemoryParts := 0
removedFileParts := 0
tb.partsLock.Lock()
tb.inmemoryParts, removedInmemoryParts = removeParts(tb.inmemoryParts, m)
tb.fileParts, removedFileParts = removeParts(tb.fileParts, m)
switch dstPartType {
case partInmemory:
tb.inmemoryParts = append(tb.inmemoryParts, pwNew)
case partFile:
tb.fileParts = append(tb.fileParts, pwNew)
default:
logger.Panicf("BUG: unknown partType=%d", dstPartType)
}
tb.notifyBackgroundMergers()
// Atomically store the updated list of file-based parts on disk.
// This must be performed under partsLock in order to prevent from races
// when multiple concurrently running goroutines update the list.
if removedFileParts > 0 || dstPartType == partFile {
mustWritePartNames(tb.fileParts, tb.path)
}
tb.partsLock.Unlock()
removedParts := removedInmemoryParts + removedFileParts
if removedParts != len(m) {
logger.Panicf("BUG: unexpected number of parts removed; got %d, want %d", removedParts, len(m))
}
// Mark old parts as must be deleted and decrement reference count,
// so they are eventually closed and deleted.
for _, pw := range pws {
atomic.StoreUint32(&pw.mustBeDeleted, 1)
pw.decRef()
}
}
func getPartsSize(pws []*partWrapper) uint64 {
n := uint64(0)
for _, pw := range pws {
n += pw.p.size
}
return n
}
func getCompressLevel(itemsCount uint64) int {
if itemsCount <= 1<<16 {
// -5 is the minimum supported compression for zstd.
// See https://github.com/facebook/zstd/releases/tag/v1.3.4
return -5
}
if itemsCount <= 1<<17 {
return -4
}
if itemsCount <= 1<<18 {
return -3
}
if itemsCount <= 1<<19 {
return -2
}
if itemsCount <= 1<<20 {
return -1
}
if itemsCount <= 1<<22 {
return 1
}
if itemsCount <= 1<<25 {
return 2
}
if itemsCount <= 1<<28 {
return 3
}
return 4
}
func (tb *Table) nextMergeIdx() uint64 {
return atomic.AddUint64(&tb.mergeIdx, 1)
}
var mergeWorkersLimitCh = make(chan struct{}, getWorkersCount())
func getWorkersCount() int {
n := cgroup.AvailableCPUs()
if n < 4 {
// Allow at least 4 merge workers on systems with small CPUs count
// in order to guarantee that background merges can be continued
// when multiple workers are busy with big merges.
n = 4
}
return n
}
func mustOpenParts(path string) []*partWrapper {
// The path can be missing after restoring from backup, so create it if needed.
fs.MustMkdirIfNotExist(path)
fs.MustRemoveTemporaryDirs(path)
// Remove txn and tmp directories, which may be left after the upgrade
// to v1.90.0 and newer versions.
fs.MustRemoveAll(filepath.Join(path, "txn"))
fs.MustRemoveAll(filepath.Join(path, "tmp"))
partNames := mustReadPartNames(path)
// Remove dirs missing in partNames. These dirs may be left after unclean shutdown
// or after the update from versions prior to v1.90.0.
des := fs.MustReadDir(path)
m := make(map[string]struct{}, len(partNames))
for _, partName := range partNames {
m[partName] = struct{}{}
}
for _, de := range des {
if !fs.IsDirOrSymlink(de) {
// Skip non-directories.
continue
}
fn := de.Name()
if _, ok := m[fn]; !ok {
deletePath := filepath.Join(path, fn)
fs.MustRemoveAll(deletePath)
}
}
fs.MustSyncPath(path)
// Open parts
var pws []*partWrapper
for _, partName := range partNames {
partPath := filepath.Join(path, partName)
p := mustOpenFilePart(partPath)
pw := &partWrapper{
p: p,
refCount: 1,
}
pws = append(pws, pw)
}
partNamesPath := filepath.Join(path, partsFilename)
if !fs.IsPathExist(partNamesPath) {
// create parts.json file on migration from previous versions before v1.90.0
mustWritePartNames(pws, path)
}
return pws
}
// CreateSnapshotAt creates tb snapshot in the given dstDir.
//
// Snapshot is created using linux hard links, so it is usually created very quickly.
//
// If deadline is reached before snapshot is created error is returned.
//
// The caller is responsible for data removal at dstDir on unsuccessful snapshot creation.
func (tb *Table) CreateSnapshotAt(dstDir string, deadline uint64) error {
logger.Infof("creating Table snapshot of %q...", tb.path)
startTime := time.Now()
var err error
srcDir := tb.path
srcDir, err = filepath.Abs(srcDir)
if err != nil {
return fmt.Errorf("cannot obtain absolute dir for %q: %w", srcDir, err)
}
dstDir, err = filepath.Abs(dstDir)
if err != nil {
return fmt.Errorf("cannot obtain absolute dir for %q: %w", dstDir, err)
}
if strings.HasPrefix(dstDir, srcDir+string(filepath.Separator)) {
return fmt.Errorf("cannot create snapshot %q inside the data dir %q", dstDir, srcDir)
}
// Flush inmemory items to disk.
tb.flushInmemoryItems()
fs.MustMkdirFailIfExist(dstDir)
pws := tb.getParts(nil)
defer tb.putParts(pws)
// Create a file with part names at dstDir
mustWritePartNames(pws, dstDir)
// Make hardlinks for pws at dstDir
for _, pw := range pws {
if pw.mp != nil {
// Skip in-memory parts
continue
}
if deadline > 0 && fasttime.UnixTimestamp() > deadline {
return fmt.Errorf("cannot create snapshot for %q: timeout exceeded", tb.path)
}
srcPartPath := pw.p.path
dstPartPath := filepath.Join(dstDir, filepath.Base(srcPartPath))
fs.MustHardLinkFiles(srcPartPath, dstPartPath)
}
fs.MustSyncPath(dstDir)
parentDir := filepath.Dir(dstDir)
fs.MustSyncPath(parentDir)
logger.Infof("created Table snapshot of %q at %q in %.3f seconds", srcDir, dstDir, time.Since(startTime).Seconds())
return nil
}
func mustWritePartNames(pws []*partWrapper, dstDir string) {
partNames := make([]string, 0, len(pws))
for _, pw := range pws {
if pw.mp != nil {
// Skip in-memory parts
continue
}
partName := filepath.Base(pw.p.path)
partNames = append(partNames, partName)
}
sort.Strings(partNames)
data, err := json.Marshal(partNames)
if err != nil {
logger.Panicf("BUG: cannot marshal partNames to JSON: %s", err)
}
partNamesPath := filepath.Join(dstDir, partsFilename)
fs.MustWriteAtomic(partNamesPath, data, true)
}
func mustReadPartNames(srcDir string) []string {
partNamesPath := filepath.Join(srcDir, partsFilename)
if fs.IsPathExist(partNamesPath) {
data, err := os.ReadFile(partNamesPath)
if err != nil {
logger.Panicf("FATAL: cannot read %s file: %s", partsFilename, err)
}
var partNames []string
if err := json.Unmarshal(data, &partNames); err != nil {
logger.Panicf("FATAL: cannot parse %s: %s", partNamesPath, err)
}
return partNames
}
// The partsFilename is missing. This is the upgrade from versions previous to v1.90.0.
// Read part names from directories under srcDir
des := fs.MustReadDir(srcDir)
var partNames []string
for _, de := range des {
if !fs.IsDirOrSymlink(de) {
// Skip non-directories.
continue
}
partName := de.Name()
if isSpecialDir(partName) {
// Skip special dirs.
continue
}
partNames = append(partNames, partName)
}
return partNames
}
// getPartsToMerge returns optimal parts to merge from pws.
//
// if isFinal is set, then merge harder.
//
// The summary size of the returned parts must be smaller than the maxOutBytes.
func getPartsToMerge(pws []*partWrapper, maxOutBytes uint64, isFinal bool) []*partWrapper {
pwsRemaining := make([]*partWrapper, 0, len(pws))
for _, pw := range pws {
if !pw.isInMerge {
pwsRemaining = append(pwsRemaining, pw)
}
}
maxPartsToMerge := defaultPartsToMerge
var dst []*partWrapper
if isFinal {
for len(dst) == 0 && maxPartsToMerge >= finalPartsToMerge {
dst = appendPartsToMerge(dst[:0], pwsRemaining, maxPartsToMerge, maxOutBytes)
maxPartsToMerge--
}
} else {
dst = appendPartsToMerge(dst[:0], pwsRemaining, maxPartsToMerge, maxOutBytes)
}
for _, pw := range dst {
if pw.isInMerge {
logger.Panicf("BUG: partWrapper.isInMerge is already set")
}
pw.isInMerge = true
}
return dst
}
// minMergeMultiplier is the minimum multiplier for the size of the output part
// compared to the size of the maximum input part for the merge.
//
// Higher value reduces write amplification (disk write IO induced by the merge),
// while increases the number of unmerged parts.
// The 1.7 is good enough for production workloads.
const minMergeMultiplier = 1.7
// appendPartsToMerge finds optimal parts to merge from src, appends
// them to dst and returns the result.
func appendPartsToMerge(dst, src []*partWrapper, maxPartsToMerge int, maxOutBytes uint64) []*partWrapper {
if len(src) < 2 {
// There is no need in merging zero or one part :)
return dst
}
if maxPartsToMerge < 2 {
logger.Panicf("BUG: maxPartsToMerge cannot be smaller than 2; got %d", maxPartsToMerge)
}
// Filter out too big parts.
// This should reduce N for O(n^2) algorithm below.
maxInPartBytes := uint64(float64(maxOutBytes) / minMergeMultiplier)
tmp := make([]*partWrapper, 0, len(src))
for _, pw := range src {
if pw.p.size > maxInPartBytes {
continue
}
tmp = append(tmp, pw)
}
src = tmp
sortPartsForOptimalMerge(src)
maxSrcParts := maxPartsToMerge
if maxSrcParts > len(src) {
maxSrcParts = len(src)
}
minSrcParts := (maxSrcParts + 1) / 2
if minSrcParts < 2 {
minSrcParts = 2
}
// Exhaustive search for parts giving the lowest write amplification when merged.
var pws []*partWrapper
maxM := float64(0)
for i := minSrcParts; i <= maxSrcParts; i++ {
for j := 0; j <= len(src)-i; j++ {
a := src[j : j+i]
if a[0].p.size*uint64(len(a)) < a[len(a)-1].p.size {
// Do not merge parts with too big difference in size,
// since this results in unbalanced merges.
continue
}
outBytes := uint64(0)
for _, pw := range a {
outBytes += pw.p.size
}
if outBytes > maxOutBytes {
// There is no sense in checking the remaining bigger parts.
break
}
m := float64(outBytes) / float64(a[len(a)-1].p.size)
if m < maxM {
continue
}
maxM = m
pws = a
}
}
minM := float64(maxPartsToMerge) / 2
if minM < minMergeMultiplier {
minM = minMergeMultiplier
}
if maxM < minM {
// There is no sense in merging parts with too small m,
// since this leads to high disk write IO.
return dst
}
return append(dst, pws...)
}
func sortPartsForOptimalMerge(pws []*partWrapper) {
// Sort src parts by size.
sort.Slice(pws, func(i, j int) bool {
return pws[i].p.size < pws[j].p.size
})
}
func removeParts(pws []*partWrapper, partsToRemove map[*partWrapper]bool) ([]*partWrapper, int) {
dst := pws[:0]
for _, pw := range pws {
if !partsToRemove[pw] {
dst = append(dst, pw)
}
}
for i := len(dst); i < len(pws); i++ {
pws[i] = nil
}
return dst, len(pws) - len(dst)
}
func isSpecialDir(name string) bool {
// Snapshots and cache dirs aren't used anymore.
// Keep them here for backwards compatibility.
return name == "tmp" || name == "txn" || name == "snapshots" || name == "cache" || fs.IsScheduledForRemoval(name)
}