path: root/swarm/storage/pyramid.go

// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package storage

import (
    "encoding/binary"
    "errors"
    "io"
    "sync"
    "time"
)

/*
   The main idea of a pyramid chunker is to process the input data without knowing the entire size apriori.
   For this to be achieved, the chunker tree is built from the ground up until the data is exhausted.
   This opens up new aveneus such as easy append and other sort of modifications to the tree thereby avoiding
   duplication of data chunks.


   Below is an example of a two level chunks tree. The leaf chunks are called data chunks and all the above
   chunks are called tree chunks. The tree chunk above data chunks is level 0 and so on until it reaches
   the root tree chunk.



                                            T10                                        <- Tree chunk lvl1
                                            |
                  __________________________|_____________________________
                 /                  |                   |                \
                /                   |                   \                 \
            __T00__             ___T01__           ___T02__           ___T03__         <- Tree chunks lvl 0
           / /     \           / /      \         / /      \         / /      \
          / /       \         / /        \       / /       \        / /        \
         D1 D2 ... D128      D1 D2 ... D128     D1 D2 ... D128     D1 D2 ... D128      <-  Data Chunks


    The split function continuously read the data and creates data chunks and send them to storage.
    When certain no of data chunks are created (defaultBranches), a signal is sent to create a tree
    entry. When the level 0 tree entries reaches certain threshold (defaultBranches), another signal
    is sent to a tree entry one level up.. and so on... until only the data is exhausted AND only one
    tree entry is present in certain level. The key of tree entry is given out as the rootKey of the file.

*/

var (
    errLoadingTreeRootChunk = errors.New("LoadTree Error: Could not load root chunk")
    errLoadingTreeChunk     = errors.New("LoadTree Error: Could not load chunk")
)

const (
    ChunkProcessors       = 8
    DefaultBranches int64 = 128
    splitTimeout          = time.Minute * 5
)

const (
    DataChunk = 0
    TreeChunk = 1
)

type ChunkerParams struct {
    Branches int64
    Hash     string
}

func NewChunkerParams() *ChunkerParams {
    return &ChunkerParams{
        Branches: DefaultBranches,
        Hash:     SHA3Hash,
    }
}

// Entry to create a tree node
type TreeEntry struct {
    level         int
    branchCount   int64
    subtreeSize   uint64
    chunk         []byte
    key           []byte
    index         int  // used in append to indicate the index of existing tree entry
    updatePending bool // indicates if the entry is loaded from existing tree
}

func NewTreeEntry(pyramid *PyramidChunker) *TreeEntry {
    return &TreeEntry{
        level:         0,
        branchCount:   0,
        subtreeSize:   0,
        chunk:         make([]byte, pyramid.chunkSize+8),
        key:           make([]byte, pyramid.hashSize),
        index:         0,
        updatePending: false,
    }
}

// Used by the hash processor to create a data/tree chunk and send to storage
type chunkJob struct {
    key       Key
    chunk     []byte
    size      int64
    parentWg  *sync.WaitGroup
    chunkType int // used to identify the tree related chunks for debugging
    chunkLvl  int // leaf-1 is level 0 and goes upwards until it reaches root
}

type PyramidChunker struct {
    hashFunc    SwarmHasher
    chunkSize   int64
    hashSize    int64
    branches    int64
    workerCount int64
    workerLock  sync.RWMutex
}

func NewPyramidChunker(params *ChunkerParams) (self *PyramidChunker) {
    self = &PyramidChunker{}
    self.hashFunc = MakeHashFunc(params.Hash)
    self.branches = params.Branches
    self.hashSize = int64(self.hashFunc().Size())
    self.chunkSize = self.hashSize * self.branches
    self.workerCount = 0
    return
}

func (self *PyramidChunker) Join(key Key, chunkC chan *Chunk) LazySectionReader {
    return &LazyChunkReader{
        key:       key,
        chunkC:    chunkC,
        chunkSize: self.chunkSize,
        branches:  self.branches,
        hashSize:  self.hashSize,
    }
}

func (self *PyramidChunker) incrementWorkerCount() {
    self.workerLock.Lock()
    defer self.workerLock.Unlock()
    self.workerCount += 1
}

func (self *PyramidChunker) getWorkerCount() int64 {
    self.workerLock.Lock()
    defer self.workerLock.Unlock()
    return self.workerCount
}

func (self *PyramidChunker) decrementWorkerCount() {
    self.workerLock.Lock()
    defer self.workerLock.Unlock()
    self.workerCount -= 1
}

func (self *PyramidChunker) Split(data io.Reader, size int64, chunkC chan *Chunk, storageWG, processorWG *sync.WaitGroup) (Key, error) {
    jobC := make(chan *chunkJob, 2*ChunkProcessors)
    wg := &sync.WaitGroup{}
    errC := make(chan error)
    quitC := make(chan bool)
    rootKey := make([]byte, self.hashSize)
    chunkLevel := make([][]*TreeEntry, self.branches)

    wg.Add(1)
    go self.prepareChunks(false, chunkLevel, data, rootKey, quitC, wg, jobC, processorWG, chunkC, errC, storageWG)

    // closes internal error channel if all subprocesses in the workgroup finished
    go func() {

        // waiting for all chunks to finish
        wg.Wait()

        // if storage waitgroup is non-nil, we wait for storage to finish too
        if storageWG != nil {
            storageWG.Wait()
        }
        //We close errC here because this is passed down to 8 parallel routines underneath.
        // if a error happens in one of them.. that particular routine raises error...
        // once they all complete successfully, the control comes back and we can safely close this here.
        close(errC)
    }()

    defer close(quitC)

    select {
    case err := <-errC:
        if err != nil {
            return nil, err
        }
    case <-time.NewTimer(splitTimeout).C:
    }
    return rootKey, nil

}

func (self *PyramidChunker) Append(key Key, data io.Reader, chunkC chan *Chunk, storageWG, processorWG *sync.WaitGroup) (Key, error) {
    quitC := make(chan bool)
    rootKey := make([]byte, self.hashSize)
    chunkLevel := make([][]*TreeEntry, self.branches)

    // Load the right most unfinished tree chunks in every level
    self.loadTree(chunkLevel, key, chunkC, quitC)

    jobC := make(chan *chunkJob, 2*ChunkProcessors)
    wg := &sync.WaitGroup{}
    errC := make(chan error)

    wg.Add(1)
    go self.prepareChunks(true, chunkLevel, data, rootKey, quitC, wg, jobC, processorWG, chunkC, errC, storageWG)

    // closes internal error channel if all subprocesses in the workgroup finished
    go func() {

        // waiting for all chunks to finish
        wg.Wait()

        // if storage waitgroup is non-nil, we wait for storage to finish too
        if storageWG != nil {
            storageWG.Wait()
        }
        close(errC)
    }()

    defer close(quitC)

    select {
    case err := <-errC:
        if err != nil {
            return nil, err
        }
    case <-time.NewTimer(splitTimeout).C:
    }
    return rootKey, nil

}

func (self *PyramidChunker) processor(id int64, jobC chan *chunkJob, chunkC chan *Chunk, errC chan error, quitC chan bool, swg, wwg *sync.WaitGroup) {
    defer self.decrementWorkerCount()

    hasher := self.hashFunc()
    if wwg != nil {
        defer wwg.Done()
    }
    for {
        select {

        case job, ok := <-jobC:
            if !ok {
                return
            }
            self.processChunk(id, hasher, job, chunkC, swg)
        case <-quitC:
            return
        }
    }
}

func (self *PyramidChunker) processChunk(id int64, hasher SwarmHash, job *chunkJob, chunkC chan *Chunk, swg *sync.WaitGroup) {
    hasher.ResetWithLength(job.chunk[:8]) // 8 bytes of length
    hasher.Write(job.chunk[8:])           // minus 8 []byte length
    h := hasher.Sum(nil)

    newChunk := &Chunk{
        Key:   h,
        SData: job.chunk,
        Size:  job.size,
        wg:    swg,
    }

    // report hash of this chunk one level up (keys corresponds to the proper subslice of the parent chunk)
    copy(job.key, h)

    // send off new chunk to storage
    if chunkC != nil {
        if swg != nil {
            swg.Add(1)
        }
    }
    job.parentWg.Done()

    if chunkC != nil {
        chunkC <- newChunk
    }
}

func (self *PyramidChunker) loadTree(chunkLevel [][]*TreeEntry, key Key, chunkC chan *Chunk, quitC chan bool) error {
    // Get the root chunk to get the total size
    chunk := retrieve(key, chunkC, quitC)
    if chunk == nil {
        return errLoadingTreeRootChunk
    }

    //if data size is less than a chunk... add a parent with update as pending
    if chunk.Size <= self.chunkSize {
        newEntry := &TreeEntry{
            level:         0,
            branchCount:   1,
            subtreeSize:   uint64(chunk.Size),
            chunk:         make([]byte, self.chunkSize+8),
            key:           make([]byte, self.hashSize),
            index:         0,
            updatePending: true,
        }
        copy(newEntry.chunk[8:], chunk.Key)
        chunkLevel[0] = append(chunkLevel[0], newEntry)
        return nil
    }

    var treeSize int64
    var depth int
    treeSize = self.chunkSize
    for ; treeSize < chunk.Size; treeSize *= self.branches {
        depth++
    }

    // Add the root chunk entry
    branchCount := int64(len(chunk.SData)-8) / self.hashSize
    newEntry := &TreeEntry{
        level:         depth - 1,
        branchCount:   branchCount,
        subtreeSize:   uint64(chunk.Size),
        chunk:         chunk.SData,
        key:           key,
        index:         0,
        updatePending: true,
    }
    chunkLevel[depth-1] = append(chunkLevel[depth-1], newEntry)

    // Add the rest of the tree
    for lvl := (depth - 1); lvl >= 1; lvl-- {

        //TODO(jmozah): instead of loading finished branches and then trim in the end,
        //avoid loading them in the first place
        for _, ent := range chunkLevel[lvl] {
            branchCount = int64(len(ent.chunk)-8) / self.hashSize
            for i := int64(0); i < branchCount; i++ {
                key := ent.chunk[8+(i*self.hashSize) : 8+((i+1)*self.hashSize)]
                newChunk := retrieve(key, chunkC, quitC)
                if newChunk == nil {
                    return errLoadingTreeChunk
                }
                bewBranchCount := int64(len(newChunk.SData)-8) / self.hashSize
                newEntry := &TreeEntry{
                    level:         lvl - 1,
                    branchCount:   bewBranchCount,
                    subtreeSize:   uint64(newChunk.Size),
                    chunk:         newChunk.SData,
                    key:           key,
                    index:         0,
                    updatePending: true,
                }
                chunkLevel[lvl-1] = append(chunkLevel[lvl-1], newEntry)

            }

            // We need to get only the right most unfinished branch.. so trim all finished branches
            if int64(len(chunkLevel[lvl-1])) >= self.branches {
                chunkLevel[lvl-1] = nil
            }
        }
    }

    return nil
}

func (self *PyramidChunker) prepareChunks(isAppend bool, chunkLevel [][]*TreeEntry, data io.Reader, rootKey []byte, quitC chan bool, wg *sync.WaitGroup, jobC chan *chunkJob, processorWG *sync.WaitGroup, chunkC chan *Chunk, errC chan error, storageWG *sync.WaitGroup) {
    defer wg.Done()

    chunkWG := &sync.WaitGroup{}
    totalDataSize := 0

    // processorWG keeps track of workers spawned for hashing chunks
    if processorWG != nil {
        processorWG.Add(1)
    }

    self.incrementWorkerCount()
    go self.processor(self.workerCount, jobC, chunkC, errC, quitC, storageWG, processorWG)

    parent := NewTreeEntry(self)
    var unFinishedChunk *Chunk

    if isAppend && len(chunkLevel[0]) != 0 {

        lastIndex := len(chunkLevel[0]) - 1
        ent := chunkLevel[0][lastIndex]

        if ent.branchCount < self.branches {
            parent = &TreeEntry{
                level:         0,
                branchCount:   ent.branchCount,
                subtreeSize:   ent.subtreeSize,
                chunk:         ent.chunk,
                key:           ent.key,
                index:         lastIndex,
                updatePending: true,
            }

            lastBranch := parent.branchCount - 1
            lastKey := parent.chunk[8+lastBranch*self.hashSize : 8+(lastBranch+1)*self.hashSize]

            unFinishedChunk = retrieve(lastKey, chunkC, quitC)
            if unFinishedChunk.Size < self.chunkSize {

                parent.subtreeSize = parent.subtreeSize - uint64(unFinishedChunk.Size)
                parent.branchCount = parent.branchCount - 1
            } else {
                unFinishedChunk = nil
            }
        }
    }

    for index := 0; ; index++ {

        var n int
        var err error
        chunkData := make([]byte, self.chunkSize+8)
        if unFinishedChunk != nil {
            copy(chunkData, unFinishedChunk.SData)
            n, err = data.Read(chunkData[8+unFinishedChunk.Size:])
            n += int(unFinishedChunk.Size)
            unFinishedChunk = nil
        } else {
            n, err = data.Read(chunkData[8:])
        }

        totalDataSize += n
        if err != nil {
            if err == io.EOF || err == io.ErrUnexpectedEOF {
                if parent.branchCount == 1 {
                    // Data is exactly one chunk.. pick the last chunk key as root
                    chunkWG.Wait()
                    lastChunksKey := parent.chunk[8 : 8+self.hashSize]
                    copy(rootKey, lastChunksKey)
                    break
                }
            } else {
                close(quitC)
                break
            }
        }

        // Data ended in chunk boundary.. just signal to start bulding tree
        if n == 0 {
            self.buildTree(isAppend, chunkLevel, parent, chunkWG, jobC, quitC, true, rootKey)
            break
        } else {

            pkey := self.enqueueDataChunk(chunkData, uint64(n), parent, chunkWG, jobC, quitC)

            // update tree related parent data structures
            parent.subtreeSize += uint64(n)
            parent.branchCount++

            // Data got exhausted... signal to send any parent tree related chunks
            if int64(n) < self.chunkSize {

                // only one data chunk .. so dont add any parent chunk
                if parent.branchCount <= 1 {
                    chunkWG.Wait()
                    copy(rootKey, pkey)
                    break
                }

                self.buildTree(isAppend, chunkLevel, parent, chunkWG, jobC, quitC, true, rootKey)
                break
            }

            if parent.branchCount == self.branches {
                self.buildTree(isAppend, chunkLevel, parent, chunkWG, jobC, quitC, false, rootKey)
                parent = NewTreeEntry(self)
            }

        }

        workers := self.getWorkerCount()
        if int64(len(jobC)) > workers && workers < ChunkProcessors {
            if processorWG != nil {
                processorWG.Add(1)
            }
            self.incrementWorkerCount()
            go self.processor(self.workerCount, jobC, chunkC, errC, quitC, storageWG, processorWG)
        }

    }

}

func (self *PyramidChunker) buildTree(isAppend bool, chunkLevel [][]*TreeEntry, ent *TreeEntry, chunkWG *sync.WaitGroup, jobC chan *chunkJob, quitC chan bool, last bool, rootKey []byte) {
    chunkWG.Wait()
    self.enqueueTreeChunk(chunkLevel, ent, chunkWG, jobC, quitC, last)

    compress := false
    endLvl := self.branches
    for lvl := int64(0); lvl < self.branches; lvl++ {
        lvlCount := int64(len(chunkLevel[lvl]))
        if lvlCount >= self.branches {
            endLvl = lvl + 1
            compress = true
            break
        }
    }

    if !compress && !last {
        return
    }

    // Wait for all the keys to be processed before compressing the tree
    chunkWG.Wait()

    for lvl := int64(ent.level); lvl < endLvl; lvl++ {

        lvlCount := int64(len(chunkLevel[lvl]))
        if lvlCount == 1 && last {
            copy(rootKey, chunkLevel[lvl][0].key)
            return
        }

        for startCount := int64(0); startCount < lvlCount; startCount += self.branches {

            endCount := startCount + self.branches
            if endCount > lvlCount {
                endCount = lvlCount
            }

            var nextLvlCount int64
            var tempEntry *TreeEntry
            if len(chunkLevel[lvl+1]) > 0 {
                nextLvlCount = int64(len(chunkLevel[lvl+1]) - 1)
                tempEntry = chunkLevel[lvl+1][nextLvlCount]
            }
            if isAppend && tempEntry != nil && tempEntry.updatePending {
                updateEntry := &TreeEntry{
                    level:         int(lvl + 1),
                    branchCount:   0,
                    subtreeSize:   0,
                    chunk:         make([]byte, self.chunkSize+8),
                    key:           make([]byte, self.hashSize),
                    index:         int(nextLvlCount),
                    updatePending: true,
                }
                for index := int64(0); index < lvlCount; index++ {
                    updateEntry.branchCount++
                    updateEntry.subtreeSize += chunkLevel[lvl][index].subtreeSize
                    copy(updateEntry.chunk[8+(index*self.hashSize):8+((index+1)*self.hashSize)], chunkLevel[lvl][index].key[:self.hashSize])
                }

                self.enqueueTreeChunk(chunkLevel, updateEntry, chunkWG, jobC, quitC, last)

            } else {

                noOfBranches := endCount - startCount
                newEntry := &TreeEntry{
                    level:         int(lvl + 1),
                    branchCount:   noOfBranches,
                    subtreeSize:   0,
                    chunk:         make([]byte, (noOfBranches*self.hashSize)+8),
                    key:           make([]byte, self.hashSize),
                    index:         int(nextLvlCount),
                    updatePending: false,
                }

                index := int64(0)
                for i := startCount; i < endCount; i++ {
                    entry := chunkLevel[lvl][i]
                    newEntry.subtreeSize += entry.subtreeSize
                    copy(newEntry.chunk[8+(index*self.hashSize):8+((index+1)*self.hashSize)], entry.key[:self.hashSize])
                    index++
                }

                self.enqueueTreeChunk(chunkLevel, newEntry, chunkWG, jobC, quitC, last)

            }

        }

        if !isAppend {
            chunkWG.Wait()
            if compress {
                chunkLevel[lvl] = nil
            }
        }
    }

}

func (self *PyramidChunker) enqueueTreeChunk(chunkLevel [][]*TreeEntry, ent *TreeEntry, chunkWG *sync.WaitGroup, jobC chan *chunkJob, quitC chan bool, last bool) {
    if ent != nil {

        // wait for data chunks to get over before processing the tree chunk
        if last {
            chunkWG.Wait()
        }

        binary.LittleEndian.PutUint64(ent.chunk[:8], ent.subtreeSize)
        ent.key = make([]byte, self.hashSize)
        chunkWG.Add(1)
        select {
        case jobC <- &chunkJob{ent.key, ent.chunk[:ent.branchCount*self.hashSize+8], int64(ent.subtreeSize), chunkWG, TreeChunk, 0}:
        case <-quitC:
        }

        // Update or append based on weather it is a new entry or being reused
        if ent.updatePending {
            chunkWG.Wait()
            chunkLevel[ent.level][ent.index] = ent
        } else {
            chunkLevel[ent.level] = append(chunkLevel[ent.level], ent)
        }

    }
}

func (self *PyramidChunker) enqueueDataChunk(chunkData []byte, size uint64, parent *TreeEntry, chunkWG *sync.WaitGroup, jobC chan *chunkJob, quitC chan bool) Key {
    binary.LittleEndian.PutUint64(chunkData[:8], size)
    pkey := parent.chunk[8+parent.branchCount*self.hashSize : 8+(parent.branchCount+1)*self.hashSize]

    chunkWG.Add(1)
    select {
    case jobC <- &chunkJob{pkey, chunkData[:size+8], int64(size), chunkWG, DataChunk, -1}:
    case <-quitC:
    }

    return pkey

}