storj/pkg/audit/cursor.go

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// Copyright (C) 2018 Storj Labs, Inc.
// See LICENSE for copying information.
package audit
import (
"context"
"crypto/rand"
"math/big"
"sync"
"github.com/vivint/infectious"
"storj.io/storj/pkg/eestream"
"storj.io/storj/pkg/paths"
"storj.io/storj/pkg/pb"
"storj.io/storj/pkg/pointerdb/pdbclient"
"storj.io/storj/pkg/storage/meta"
)
// Stripe keeps track of a stripe's index and its parent segment
type Stripe struct {
Index int
Segment *pb.Pointer
}
// Cursor keeps track of audit location in pointer db
type Cursor struct {
pointers pdbclient.Client
lastPath *paths.Path
mutex sync.Mutex
}
// NewCursor creates a Cursor which iterates over pointer db
func NewCursor(pointers pdbclient.Client) *Cursor {
return &Cursor{pointers: pointers}
}
// NextStripe returns a random stripe to be audited
func (cursor *Cursor) NextStripe(ctx context.Context) (stripe *Stripe, err error) {
cursor.mutex.Lock()
defer cursor.mutex.Unlock()
var pointerItems []pdbclient.ListItem
var path paths.Path
var more bool
if cursor.lastPath == nil {
pointerItems, more, err = cursor.pointers.List(ctx, nil, nil, nil, true, 0, meta.None)
} else {
pointerItems, more, err = cursor.pointers.List(ctx, nil, *cursor.lastPath, nil, true, 0, meta.None)
}
if err != nil {
return nil, err
}
// get random pointer
pointerItem, err := getRandomPointer(pointerItems)
if err != nil {
return nil, err
}
// get path
path = pointerItem.Path
// keep track of last path listed
if !more {
cursor.lastPath = nil
} else {
cursor.lastPath = &pointerItems[len(pointerItems)-1].Path
}
// get pointer info
pointer, err := cursor.pointers.Get(ctx, path)
if err != nil {
return nil, err
}
// create the erasure scheme so we can get the stripe size
es, err := makeErasureScheme(pointer.GetRemote().GetRedundancy())
if err != nil {
return nil, err
}
//get random stripe
index, err := getRandomStripe(es, pointer)
if err != nil {
return nil, err
}
return &Stripe{Index: index, Segment: pointer}, nil
}
// create the erasure scheme
func makeErasureScheme(rs *pb.RedundancyScheme) (eestream.ErasureScheme, error) {
fc, err := infectious.NewFEC(int(rs.GetMinReq()), int(rs.GetTotal()))
if err != nil {
return nil, err
}
es := eestream.NewRSScheme(fc, int(rs.GetErasureShareSize()))
return es, nil
}
func getRandomStripe(es eestream.ErasureScheme, pointer *pb.Pointer) (index int, err error) {
stripeSize := es.StripeSize()
randomStripeIndex, err := rand.Int(rand.Reader, big.NewInt(pointer.GetSize()/int64(stripeSize)))
if err != nil {
return -1, err
}
return int(randomStripeIndex.Int64()), nil
}
func getRandomPointer(pointerItems []pdbclient.ListItem) (pointer pdbclient.ListItem, err error) {
randomNum, err := rand.Int(rand.Reader, big.NewInt(int64(len(pointerItems))))
if err != nil {
return pdbclient.ListItem{}, err
}
randomNumInt64 := randomNum.Int64()
pointerItem := pointerItems[randomNumInt64]
return pointerItem, nil
}