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blockstore.go
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blockstore.go
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// Package blockstore implements a thin wrapper over a datastore, giving a
// clean interface for Getting and Putting block objects.
package blockstore
import (
"context"
"errors"
"sync"
"sync/atomic"
blocks "github.com/ipfs/go-ipfs/blocks"
dshelp "github.com/ipfs/go-ipfs/thirdparty/ds-help"
ds "gx/ipfs/QmRWDav6mzWseLWeYfVd5fvUKiVe9xNH29YfMF438fG364/go-datastore"
dsns "gx/ipfs/QmRWDav6mzWseLWeYfVd5fvUKiVe9xNH29YfMF438fG364/go-datastore/namespace"
dsq "gx/ipfs/QmRWDav6mzWseLWeYfVd5fvUKiVe9xNH29YfMF438fG364/go-datastore/query"
logging "gx/ipfs/QmSpJByNKFX1sCsHBEp3R73FL4NF6FnQTEGyNAXHm2GS52/go-log"
cid "gx/ipfs/QmYhQaCYEcaPPjxJX7YcPcVKkQfRy6sJ7B3XmGFk82XYdQ/go-cid"
)
var log = logging.Logger("blockstore")
// BlockPrefix namespaces blockstore datastores
var BlockPrefix = ds.NewKey("blocks")
// ErrValueTypeMismatch is an error returned when the item retrieved from
// the datatstore is not a block.
var ErrValueTypeMismatch = errors.New("the retrieved value is not a Block")
// ErrHashMismatch is an error returned when the hash of a block
// is different than expected.
var ErrHashMismatch = errors.New("block in storage has different hash than requested")
// ErrNotFound is an error returned when a block is not found.
var ErrNotFound = errors.New("blockstore: block not found")
// Blockstore wraps a Datastore block-centered methods and provides a layer
// of abstraction which allows to add different caching strategies.
type Blockstore interface {
DeleteBlock(*cid.Cid) error
Has(*cid.Cid) (bool, error)
Get(*cid.Cid) (blocks.Block, error)
Put(blocks.Block) error
PutMany([]blocks.Block) error
// AllKeysChan returns a channel from which
// the CIDs in the Blockstore can be read. It should respect
// the given context, closing the channel if it becomes Done.
AllKeysChan(ctx context.Context) (<-chan *cid.Cid, error)
// HashOnRead specifies if every read block should be
// rehashed to make sure it matches its CID.
HashOnRead(enabled bool)
}
// GCLocker abstract functionality to lock a blockstore when performing
// garbage-collection operations.
type GCLocker interface {
// GCLock locks the blockstore for garbage collection. No operations
// that expect to finish with a pin should ocurr simultaneously.
// Reading during GC is safe, and requires no lock.
GCLock() Unlocker
// PinLock locks the blockstore for sequences of puts expected to finish
// with a pin (before GC). Multiple put->pin sequences can write through
// at the same time, but no GC should not happen simulatenously.
// Reading during Pinning is safe, and requires no lock.
PinLock() Unlocker
// GcRequested returns true if GCLock has been called and is waiting to
// take the lock
GCRequested() bool
}
// GCBlockstore is a blockstore that can safely run garbage-collection
// operations.
type GCBlockstore interface {
Blockstore
GCLocker
}
// NewGCBlockstore returns a default implementation of GCBlockstore
// using the given Blockstore and GCLocker.
func NewGCBlockstore(bs Blockstore, gcl GCLocker) GCBlockstore {
return gcBlockstore{bs, gcl}
}
type gcBlockstore struct {
Blockstore
GCLocker
}
// NewBlockstore returns a default Blockstore implementation
// using the provided datastore.Batching backend.
func NewBlockstore(d ds.Batching) Blockstore {
var dsb ds.Batching
dd := dsns.Wrap(d, BlockPrefix)
dsb = dd
return &blockstore{
datastore: dsb,
}
}
type blockstore struct {
datastore ds.Batching
rehash bool
}
func (bs *blockstore) HashOnRead(enabled bool) {
bs.rehash = enabled
}
func (bs *blockstore) Get(k *cid.Cid) (blocks.Block, error) {
if k == nil {
log.Error("nil cid in blockstore")
return nil, ErrNotFound
}
maybeData, err := bs.datastore.Get(dshelp.CidToDsKey(k))
if err == ds.ErrNotFound {
return nil, ErrNotFound
}
if err != nil {
return nil, err
}
bdata, ok := maybeData.([]byte)
if !ok {
return nil, ErrValueTypeMismatch
}
if bs.rehash {
rbcid, err := k.Prefix().Sum(bdata)
if err != nil {
return nil, err
}
if !rbcid.Equals(k) {
return nil, ErrHashMismatch
}
return blocks.NewBlockWithCid(bdata, rbcid)
}
return blocks.NewBlockWithCid(bdata, k)
}
func (bs *blockstore) Put(block blocks.Block) error {
k := dshelp.CidToDsKey(block.Cid())
// Has is cheaper than Put, so see if we already have it
exists, err := bs.datastore.Has(k)
if err == nil && exists {
return nil // already stored.
}
return bs.datastore.Put(k, block.RawData())
}
func (bs *blockstore) PutMany(blocks []blocks.Block) error {
t, err := bs.datastore.Batch()
if err != nil {
return err
}
for _, b := range blocks {
k := dshelp.CidToDsKey(b.Cid())
exists, err := bs.datastore.Has(k)
if err == nil && exists {
continue
}
err = t.Put(k, b.RawData())
if err != nil {
return err
}
}
return t.Commit()
}
func (bs *blockstore) Has(k *cid.Cid) (bool, error) {
return bs.datastore.Has(dshelp.CidToDsKey(k))
}
func (bs *blockstore) DeleteBlock(k *cid.Cid) error {
err := bs.datastore.Delete(dshelp.CidToDsKey(k))
if err == ds.ErrNotFound {
return ErrNotFound
}
return err
}
// AllKeysChan runs a query for keys from the blockstore.
// this is very simplistic, in the future, take dsq.Query as a param?
//
// AllKeysChan respects context.
func (bs *blockstore) AllKeysChan(ctx context.Context) (<-chan *cid.Cid, error) {
// KeysOnly, because that would be _a lot_ of data.
q := dsq.Query{KeysOnly: true}
// datastore/namespace does *NOT* fix up Query.Prefix
q.Prefix = BlockPrefix.String()
res, err := bs.datastore.Query(q)
if err != nil {
return nil, err
}
output := make(chan *cid.Cid, dsq.KeysOnlyBufSize)
go func() {
defer func() {
res.Close() // ensure exit (signals early exit, too)
close(output)
}()
for {
e, ok := res.NextSync()
if !ok {
return
}
if e.Error != nil {
log.Errorf("blockstore.AllKeysChan got err: %s", e.Error)
return
}
// need to convert to key.Key using key.KeyFromDsKey.
k, err := dshelp.DsKeyToCid(ds.RawKey(e.Key))
if err != nil {
log.Warningf("error parsing key from DsKey: %s", err)
continue
}
select {
case <-ctx.Done():
return
case output <- k:
}
}
}()
return output, nil
}
// NewGCLocker returns a default implementation of
// GCLocker using standard [RW] mutexes.
func NewGCLocker() GCLocker {
return &gclocker{}
}
type gclocker struct {
lk sync.RWMutex
gcreq int32
}
// Unlocker represents an object which can Unlock
// something.
type Unlocker interface {
Unlock()
}
type unlocker struct {
unlock func()
}
func (u *unlocker) Unlock() {
u.unlock()
u.unlock = nil // ensure its not called twice
}
func (bs *gclocker) GCLock() Unlocker {
atomic.AddInt32(&bs.gcreq, 1)
bs.lk.Lock()
atomic.AddInt32(&bs.gcreq, -1)
return &unlocker{bs.lk.Unlock}
}
func (bs *gclocker) PinLock() Unlocker {
bs.lk.RLock()
return &unlocker{bs.lk.RUnlock}
}
func (bs *gclocker) GCRequested() bool {
return atomic.LoadInt32(&bs.gcreq) > 0
}