forked from ipfs/kubo
/
merkledag.go
392 lines (338 loc) · 10 KB
/
merkledag.go
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// Package merkledag implements the IPFS Merkle DAG data structures.
package merkledag
import (
"context"
"fmt"
"sync"
bserv "github.com/ipfs/go-ipfs/blockservice"
blocks "gx/ipfs/QmVzK524a2VWLqyvtBeiHKsUAWYgeAk4DBeZoY7vpNPNRx/go-block-format"
ipldcbor "gx/ipfs/QmWrbExtUaQQHjJ8FVVDAWj5o1MRAELDUV3VmoQsZHHb6L/go-ipld-cbor"
cid "gx/ipfs/QmYVNvtQkeZ6AKSwDrjQTs432QtL6umrrK41EBq3cu7iSP/go-cid"
ipld "gx/ipfs/QmZtNq8dArGfnpCZfx2pUNY7UcjGhVp5qqwQ4hH6mpTMRQ/go-ipld-format"
)
// TODO: We should move these registrations elsewhere. Really, most of the IPLD
// functionality should go in a `go-ipld` repo but that will take a lot of work
// and design.
func init() {
ipld.Register(cid.DagProtobuf, DecodeProtobufBlock)
ipld.Register(cid.Raw, DecodeRawBlock)
ipld.Register(cid.DagCBOR, ipldcbor.DecodeBlock)
}
// contextKey is a type to use as value for the ProgressTracker contexts.
type contextKey string
const progressContextKey contextKey = "progress"
// NewDAGService constructs a new DAGService (using the default implementation).
// Note that the default implementation is also an ipld.LinkGetter.
func NewDAGService(bs bserv.BlockService) *dagService {
return &dagService{Blocks: bs}
}
// dagService is an IPFS Merkle DAG service.
// - the root is virtual (like a forest)
// - stores nodes' data in a BlockService
// TODO: should cache Nodes that are in memory, and be
// able to free some of them when vm pressure is high
type dagService struct {
Blocks bserv.BlockService
}
// Add adds a node to the dagService, storing the block in the BlockService
func (n *dagService) Add(ctx context.Context, nd ipld.Node) error {
if n == nil { // FIXME remove this assertion. protect with constructor invariant
return fmt.Errorf("dagService is nil")
}
return n.Blocks.AddBlock(nd)
}
func (n *dagService) AddMany(ctx context.Context, nds []ipld.Node) error {
blks := make([]blocks.Block, len(nds))
for i, nd := range nds {
blks[i] = nd
}
return n.Blocks.AddBlocks(blks)
}
// Get retrieves a node from the dagService, fetching the block in the BlockService
func (n *dagService) Get(ctx context.Context, c *cid.Cid) (ipld.Node, error) {
if n == nil {
return nil, fmt.Errorf("dagService is nil")
}
ctx, cancel := context.WithCancel(ctx)
defer cancel()
b, err := n.Blocks.GetBlock(ctx, c)
if err != nil {
if err == bserv.ErrNotFound {
return nil, ipld.ErrNotFound
}
return nil, fmt.Errorf("failed to get block for %s: %v", c, err)
}
return ipld.Decode(b)
}
// GetLinks return the links for the node, the node doesn't necessarily have
// to exist locally.
func (n *dagService) GetLinks(ctx context.Context, c *cid.Cid) ([]*ipld.Link, error) {
if c.Type() == cid.Raw {
return nil, nil
}
node, err := n.Get(ctx, c)
if err != nil {
return nil, err
}
return node.Links(), nil
}
func (n *dagService) Remove(ctx context.Context, c *cid.Cid) error {
return n.Blocks.DeleteBlock(c)
}
// RemoveMany removes multiple nodes from the DAG. It will likely be faster than
// removing them individually.
//
// This operation is not atomic. If it returns an error, some nodes may or may
// not have been removed.
func (n *dagService) RemoveMany(ctx context.Context, cids []*cid.Cid) error {
// TODO(#4608): make this batch all the way down.
for _, c := range cids {
if err := n.Blocks.DeleteBlock(c); err != nil {
return err
}
}
return nil
}
// GetLinksDirect creates a function to get the links for a node, from
// the node, bypassing the LinkService. If the node does not exist
// locally (and can not be retrieved) an error will be returned.
func GetLinksDirect(serv ipld.NodeGetter) GetLinks {
return func(ctx context.Context, c *cid.Cid) ([]*ipld.Link, error) {
nd, err := serv.Get(ctx, c)
if err != nil {
if err == bserv.ErrNotFound {
err = ipld.ErrNotFound
}
return nil, err
}
return nd.Links(), nil
}
}
type sesGetter struct {
bs *bserv.Session
}
// Get gets a single node from the DAG.
func (sg *sesGetter) Get(ctx context.Context, c *cid.Cid) (ipld.Node, error) {
blk, err := sg.bs.GetBlock(ctx, c)
switch err {
case bserv.ErrNotFound:
return nil, ipld.ErrNotFound
default:
return nil, err
case nil:
// noop
}
return ipld.Decode(blk)
}
// GetMany gets many nodes at once, batching the request if possible.
func (sg *sesGetter) GetMany(ctx context.Context, keys []*cid.Cid) <-chan *ipld.NodeOption {
return getNodesFromBG(ctx, sg.bs, keys)
}
// Session returns a NodeGetter using a new session for block fetches.
func (n *dagService) Session(ctx context.Context) ipld.NodeGetter {
return &sesGetter{bserv.NewSession(ctx, n.Blocks)}
}
// FetchGraph fetches all nodes that are children of the given node
func FetchGraph(ctx context.Context, root *cid.Cid, serv ipld.DAGService) error {
var ng ipld.NodeGetter = serv
ds, ok := serv.(*dagService)
if ok {
ng = &sesGetter{bserv.NewSession(ctx, ds.Blocks)}
}
v, _ := ctx.Value(progressContextKey).(*ProgressTracker)
if v == nil {
return EnumerateChildrenAsync(ctx, GetLinksDirect(ng), root, cid.NewSet().Visit)
}
set := cid.NewSet()
visit := func(c *cid.Cid) bool {
if set.Visit(c) {
v.Increment()
return true
}
return false
}
return EnumerateChildrenAsync(ctx, GetLinksDirect(ng), root, visit)
}
// GetMany gets many nodes from the DAG at once.
//
// This method may not return all requested nodes (and may or may not return an
// error indicating that it failed to do so. It is up to the caller to verify
// that it received all nodes.
func (n *dagService) GetMany(ctx context.Context, keys []*cid.Cid) <-chan *ipld.NodeOption {
return getNodesFromBG(ctx, n.Blocks, keys)
}
func dedupKeys(keys []*cid.Cid) []*cid.Cid {
set := cid.NewSet()
for _, c := range keys {
set.Add(c)
}
if set.Len() == len(keys) {
return keys
}
return set.Keys()
}
func getNodesFromBG(ctx context.Context, bs bserv.BlockGetter, keys []*cid.Cid) <-chan *ipld.NodeOption {
keys = dedupKeys(keys)
out := make(chan *ipld.NodeOption, len(keys))
blocks := bs.GetBlocks(ctx, keys)
var count int
go func() {
defer close(out)
for {
select {
case b, ok := <-blocks:
if !ok {
if count != len(keys) {
out <- &ipld.NodeOption{Err: fmt.Errorf("failed to fetch all nodes")}
}
return
}
nd, err := ipld.Decode(b)
if err != nil {
out <- &ipld.NodeOption{Err: err}
return
}
out <- &ipld.NodeOption{Node: nd}
count++
case <-ctx.Done():
out <- &ipld.NodeOption{Err: ctx.Err()}
return
}
}
}()
return out
}
// GetLinks is the type of function passed to the EnumerateChildren function(s)
// for getting the children of an IPLD node.
type GetLinks func(context.Context, *cid.Cid) ([]*ipld.Link, error)
// GetLinksWithDAG returns a GetLinks function that tries to use the given
// NodeGetter as a LinkGetter to get the children of a given IPLD node. This may
// allow us to traverse the DAG without actually loading and parsing the node in
// question (if we already have the links cached).
func GetLinksWithDAG(ng ipld.NodeGetter) GetLinks {
return func(ctx context.Context, c *cid.Cid) ([]*ipld.Link, error) {
return ipld.GetLinks(ctx, ng, c)
}
}
// EnumerateChildren will walk the dag below the given root node and add all
// unseen children to the passed in set.
// TODO: parallelize to avoid disk latency perf hits?
func EnumerateChildren(ctx context.Context, getLinks GetLinks, root *cid.Cid, visit func(*cid.Cid) bool) error {
links, err := getLinks(ctx, root)
if err != nil {
return err
}
for _, lnk := range links {
c := lnk.Cid
if visit(c) {
err = EnumerateChildren(ctx, getLinks, c, visit)
if err != nil {
return err
}
}
}
return nil
}
// ProgressTracker is used to show progress when fetching nodes.
type ProgressTracker struct {
Total int
lk sync.Mutex
}
// DeriveContext returns a new context with value "progress" derived from
// the given one.
func (p *ProgressTracker) DeriveContext(ctx context.Context) context.Context {
return context.WithValue(ctx, progressContextKey, p)
}
// Increment adds one to the total progress.
func (p *ProgressTracker) Increment() {
p.lk.Lock()
defer p.lk.Unlock()
p.Total++
}
// Value returns the current progress.
func (p *ProgressTracker) Value() int {
p.lk.Lock()
defer p.lk.Unlock()
return p.Total
}
// FetchGraphConcurrency is total number of concurrent fetches that
// 'fetchNodes' will start at a time
var FetchGraphConcurrency = 8
// EnumerateChildrenAsync is equivalent to EnumerateChildren *except* that it
// fetches children in parallel.
//
// NOTE: It *does not* make multiple concurrent calls to the passed `visit` function.
func EnumerateChildrenAsync(ctx context.Context, getLinks GetLinks, c *cid.Cid, visit func(*cid.Cid) bool) error {
feed := make(chan *cid.Cid)
out := make(chan []*ipld.Link)
done := make(chan struct{})
var setlk sync.Mutex
errChan := make(chan error)
fetchersCtx, cancel := context.WithCancel(ctx)
defer cancel()
for i := 0; i < FetchGraphConcurrency; i++ {
go func() {
for ic := range feed {
setlk.Lock()
shouldVisit := visit(ic)
setlk.Unlock()
if shouldVisit {
links, err := getLinks(ctx, ic)
if err != nil {
errChan <- err
return
}
select {
case out <- links:
case <-fetchersCtx.Done():
return
}
}
select {
case done <- struct{}{}:
case <-fetchersCtx.Done():
}
}
}()
}
defer close(feed)
send := feed
var todobuffer []*cid.Cid
var inProgress int
next := c
for {
select {
case send <- next:
inProgress++
if len(todobuffer) > 0 {
next = todobuffer[0]
todobuffer = todobuffer[1:]
} else {
next = nil
send = nil
}
case <-done:
inProgress--
if inProgress == 0 && next == nil {
return nil
}
case links := <-out:
for _, lnk := range links {
if next == nil {
next = lnk.Cid
send = feed
} else {
todobuffer = append(todobuffer, lnk.Cid)
}
}
case err := <-errChan:
return err
case <-ctx.Done():
return ctx.Err()
}
}
}
var _ ipld.LinkGetter = &dagService{}
var _ ipld.NodeGetter = &dagService{}
var _ ipld.NodeGetter = &sesGetter{}
var _ ipld.DAGService = &dagService{}