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package statesync
import (
"errors"
"fmt"
"io/ioutil"
"os"
"path/filepath"
"strconv"
"time"
tmsync "github.com/tendermint/tendermint/libs/sync"
"github.com/tendermint/tendermint/p2p"
)
// errDone is returned by chunkQueue.Next() when all chunks have been returned.
var errDone = errors.New("chunk queue has completed")
// chunk contains data for a chunk.
type chunk struct {
Height uint64
Format uint32
Index uint32
Chunk []byte
Sender p2p.PeerID
}
// chunkQueue manages chunks for a state sync process, ordering them if requested. It acts as an
// iterator over all chunks, but callers can request chunks to be retried, optionally after
// refetching.
type chunkQueue struct {
tmsync.Mutex
snapshot *snapshot // if this is nil, the queue has been closed
dir string // temp dir for on-disk chunk storage
chunkFiles map[uint32]string // path to temporary chunk file
chunkSenders map[uint32]p2p.PeerID // the peer who sent the given chunk
chunkAllocated map[uint32]bool // chunks that have been allocated via Allocate()
chunkReturned map[uint32]bool // chunks returned via Next()
waiters map[uint32][]chan<- uint32 // signals WaitFor() waiters about chunk arrival
}
// newChunkQueue creates a new chunk queue for a snapshot, using a temp dir for storage.
// Callers must call Close() when done.
func newChunkQueue(snapshot *snapshot, tempDir string) (*chunkQueue, error) {
dir, err := ioutil.TempDir(tempDir, "tm-statesync")
if err != nil {
return nil, fmt.Errorf("unable to create temp dir for state sync chunks: %w", err)
}
if snapshot.Chunks == 0 {
return nil, errors.New("snapshot has no chunks")
}
return &chunkQueue{
snapshot: snapshot,
dir: dir,
chunkFiles: make(map[uint32]string, snapshot.Chunks),
chunkSenders: make(map[uint32]p2p.PeerID, snapshot.Chunks),
chunkAllocated: make(map[uint32]bool, snapshot.Chunks),
chunkReturned: make(map[uint32]bool, snapshot.Chunks),
waiters: make(map[uint32][]chan<- uint32),
}, nil
}
// Add adds a chunk to the queue. It ignores chunks that already exist, returning false.
func (q *chunkQueue) Add(chunk *chunk) (bool, error) {
if chunk == nil || chunk.Chunk == nil {
return false, errors.New("cannot add nil chunk")
}
q.Lock()
defer q.Unlock()
if q.snapshot == nil {
return false, nil // queue is closed
}
if chunk.Height != q.snapshot.Height {
return false, fmt.Errorf("invalid chunk height %v, expected %v", chunk.Height, q.snapshot.Height)
}
if chunk.Format != q.snapshot.Format {
return false, fmt.Errorf("invalid chunk format %v, expected %v", chunk.Format, q.snapshot.Format)
}
if chunk.Index >= q.snapshot.Chunks {
return false, fmt.Errorf("received unexpected chunk %v", chunk.Index)
}
if q.chunkFiles[chunk.Index] != "" {
return false, nil
}
path := filepath.Join(q.dir, strconv.FormatUint(uint64(chunk.Index), 10))
err := ioutil.WriteFile(path, chunk.Chunk, 0600)
if err != nil {
return false, fmt.Errorf("failed to save chunk %v to file %v: %w", chunk.Index, path, err)
}
q.chunkFiles[chunk.Index] = path
q.chunkSenders[chunk.Index] = chunk.Sender
// Signal any waiters that the chunk has arrived.
for _, waiter := range q.waiters[chunk.Index] {
waiter <- chunk.Index
close(waiter)
}
delete(q.waiters, chunk.Index)
return true, nil
}
// Allocate allocates a chunk to the caller, making it responsible for fetching it. Returns
// errDone once no chunks are left or the queue is closed.
func (q *chunkQueue) Allocate() (uint32, error) {
q.Lock()
defer q.Unlock()
if q.snapshot == nil {
return 0, errDone
}
if uint32(len(q.chunkAllocated)) >= q.snapshot.Chunks {
return 0, errDone
}
for i := uint32(0); i < q.snapshot.Chunks; i++ {
if !q.chunkAllocated[i] {
q.chunkAllocated[i] = true
return i, nil
}
}
return 0, errDone
}
// Close closes the chunk queue, cleaning up all temporary files.
func (q *chunkQueue) Close() error {
q.Lock()
defer q.Unlock()
if q.snapshot == nil {
return nil
}
for _, waiters := range q.waiters {
for _, waiter := range waiters {
close(waiter)
}
}
q.waiters = nil
q.snapshot = nil
if err := os.RemoveAll(q.dir); err != nil {
return fmt.Errorf("failed to clean up state sync tempdir %v: %w", q.dir, err)
}
return nil
}
// Discard discards a chunk. It will be removed from the queue, available for allocation, and can
// be added and returned via Next() again. If the chunk is not already in the queue this does
// nothing, to avoid it being allocated to multiple fetchers.
func (q *chunkQueue) Discard(index uint32) error {
q.Lock()
defer q.Unlock()
return q.discard(index)
}
// discard discards a chunk, scheduling it for refetching. The caller must hold the mutex lock.
func (q *chunkQueue) discard(index uint32) error {
if q.snapshot == nil {
return nil
}
path := q.chunkFiles[index]
if path == "" {
return nil
}
if err := os.Remove(path); err != nil {
return fmt.Errorf("failed to remove chunk %v: %w", index, err)
}
delete(q.chunkFiles, index)
delete(q.chunkReturned, index)
delete(q.chunkAllocated, index)
return nil
}
// DiscardSender discards all *unreturned* chunks from a given sender. If the caller wants to
// discard already returned chunks, this can be done via Discard().
func (q *chunkQueue) DiscardSender(peerID p2p.PeerID) error {
q.Lock()
defer q.Unlock()
for index, sender := range q.chunkSenders {
if sender.Equal(peerID) && !q.chunkReturned[index] {
err := q.discard(index)
if err != nil {
return err
}
delete(q.chunkSenders, index)
}
}
return nil
}
// GetSender returns the sender of the chunk with the given index, or empty if
// not found.
func (q *chunkQueue) GetSender(index uint32) p2p.PeerID {
q.Lock()
defer q.Unlock()
return q.chunkSenders[index]
}
// Has checks whether a chunk exists in the queue.
func (q *chunkQueue) Has(index uint32) bool {
q.Lock()
defer q.Unlock()
return q.chunkFiles[index] != ""
}
// load loads a chunk from disk, or nil if the chunk is not in the queue. The caller must hold the
// mutex lock.
func (q *chunkQueue) load(index uint32) (*chunk, error) {
path, ok := q.chunkFiles[index]
if !ok {
return nil, nil
}
body, err := ioutil.ReadFile(path)
if err != nil {
return nil, fmt.Errorf("failed to load chunk %v: %w", index, err)
}
return &chunk{
Height: q.snapshot.Height,
Format: q.snapshot.Format,
Index: index,
Chunk: body,
Sender: q.chunkSenders[index],
}, nil
}
// Next returns the next chunk from the queue, or errDone if all chunks have been returned. It
// blocks until the chunk is available. Concurrent Next() calls may return the same chunk.
func (q *chunkQueue) Next() (*chunk, error) {
q.Lock()
var chunk *chunk
index, err := q.nextUp()
if err == nil {
chunk, err = q.load(index)
if err == nil {
q.chunkReturned[index] = true
}
}
q.Unlock()
if chunk != nil || err != nil {
return chunk, err
}
select {
case _, ok := <-q.WaitFor(index):
if !ok {
return nil, errDone // queue closed
}
case <-time.After(chunkTimeout):
return nil, errTimeout
}
q.Lock()
defer q.Unlock()
chunk, err = q.load(index)
if err != nil {
return nil, err
}
q.chunkReturned[index] = true
return chunk, nil
}
// nextUp returns the next chunk to be returned, or errDone if all chunks have been returned. The
// caller must hold the mutex lock.
func (q *chunkQueue) nextUp() (uint32, error) {
if q.snapshot == nil {
return 0, errDone
}
for i := uint32(0); i < q.snapshot.Chunks; i++ {
if !q.chunkReturned[i] {
return i, nil
}
}
return 0, errDone
}
// Retry schedules a chunk to be retried, without refetching it.
func (q *chunkQueue) Retry(index uint32) {
q.Lock()
defer q.Unlock()
delete(q.chunkReturned, index)
}
// RetryAll schedules all chunks to be retried, without refetching them.
func (q *chunkQueue) RetryAll() {
q.Lock()
defer q.Unlock()
q.chunkReturned = make(map[uint32]bool)
}
// Size returns the total number of chunks for the snapshot and queue, or 0 when closed.
func (q *chunkQueue) Size() uint32 {
q.Lock()
defer q.Unlock()
if q.snapshot == nil {
return 0
}
return q.snapshot.Chunks
}
// WaitFor returns a channel that receives a chunk index when it arrives in the queue, or
// immediately if it has already arrived. The channel is closed without a value if the queue is
// closed or if the chunk index is not valid.
func (q *chunkQueue) WaitFor(index uint32) <-chan uint32 {
q.Lock()
defer q.Unlock()
ch := make(chan uint32, 1)
switch {
case q.snapshot == nil:
close(ch)
case index >= q.snapshot.Chunks:
close(ch)
case q.chunkFiles[index] != "":
ch <- index
close(ch)
default:
if q.waiters[index] == nil {
q.waiters[index] = make([]chan<- uint32, 0)
}
q.waiters[index] = append(q.waiters[index], ch)
}
return ch
}