// Copyright 2018 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/>.
// Handler is the API for Mutable Resources
// It enables creating, updating, syncing and retrieving resources and their update data
package mru
import (
"bytes"
"context"
"fmt"
"sync"
"time"
"github.com/ethereum/go-ethereum/swarm/storage/mru/lookup"
"github.com/ethereum/go-ethereum/swarm/log"
"github.com/ethereum/go-ethereum/swarm/storage"
)
type Handler struct {
chunkStore *storage.NetStore
HashSize int
cache map[uint64]*cacheEntry
cacheLock sync.RWMutex
storeTimeout time.Duration
queryMaxPeriods uint32
}
// HandlerParams pass parameters to the Handler constructor NewHandler
// Signer and TimestampProvider are mandatory parameters
type HandlerParams struct {
}
// hashPool contains a pool of ready hashers
var hashPool sync.Pool
// init initializes the package and hashPool
func init() {
hashPool = sync.Pool{
New: func() interface{} {
return storage.MakeHashFunc(feedsHashAlgorithm)()
},
}
}
// NewHandler creates a new Swarm Feeds API
func NewHandler(params *HandlerParams) *Handler {
fh := &Handler{
cache: make(map[uint64]*cacheEntry),
}
for i := 0; i < hasherCount; i++ {
hashfunc := storage.MakeHashFunc(feedsHashAlgorithm)()
if fh.HashSize == 0 {
fh.HashSize = hashfunc.Size()
}
hashPool.Put(hashfunc)
}
return fh
}
// SetStore sets the store backend for the Swarm Feeds API
func (h *Handler) SetStore(store *storage.NetStore) {
h.chunkStore = store
}
// Validate is a chunk validation method
// If it looks like a feed update, the chunk address is checked against the userAddr of the update's signature
// It implements the storage.ChunkValidator interface
func (h *Handler) Validate(chunkAddr storage.Address, data []byte) bool {
dataLength := len(data)
if dataLength < minimumSignedUpdateLength {
return false
}
// check if it is a properly formatted update chunk with
// valid signature and proof of ownership of the feed it is trying
// to update
// First, deserialize the chunk
var r Request
if err := r.fromChunk(chunkAddr, data); err != nil {
log.Debug("Invalid feed update chunk", "addr", chunkAddr.Hex(), "err", err.Error())
return false
}
// Verify signatures and that the signer actually owns the feed
// If it fails, it means either the signature is not valid, data is corrupted
// or someone is trying to update someone else's feed.
if err := r.Verify(); err != nil {
log.Debug("Invalid feed update signature", "err", err)
return false
}
return true
}
// GetContent retrieves the data payload of the last synced update of the Feed
func (h *Handler) GetContent(feed *Feed) (storage.Address, []byte, error) {
if feed == nil {
return nil, nil, NewError(ErrInvalidValue, "feed is nil")
}
feedUpdate := h.get(feed)
if feedUpdate == nil {
return nil, nil, NewError(ErrNotFound, "feed update not cached")
}
return feedUpdate.lastKey, feedUpdate.data, nil
}
// NewRequest prepares a Request structure with all the necessary information to
// just add the desired data and sign it.
// The resulting structure can then be signed and passed to Handler.Update to be verified and sent
func (h *Handler) NewRequest(ctx context.Context, feed *Feed) (request *Request, err error) {
if feed == nil {
return nil, NewError(ErrInvalidValue, "feed cannot be nil")
}
now := TimestampProvider.Now().Time
request = new(Request)
request.Header.Version = ProtocolVersion
query := NewQueryLatest(feed, lookup.NoClue)
feedUpdate, err := h.Lookup(ctx, query)
if err != nil {
if err.(*Error).code != ErrNotFound {
return nil, err
}
// not finding updates means that there is a network error
// or that the feed really does not have updates
}
request.Feed = *feed
// if we already have an update, then find next epoch
if feedUpdate != nil {
request.Epoch = lookup.GetNextEpoch(feedUpdate.Epoch, now)
} else {
request.Epoch = lookup.GetFirstEpoch(now)
}
return request, nil
}
// Lookup retrieves a specific or latest feed update
// Lookup works differently depending on the configuration of `query`
// See the `query` documentation and helper functions:
// `NewQueryLatest` and `NewQuery`
func (h *Handler) Lookup(ctx context.Context, query *Query) (*cacheEntry, error) {
timeLimit := query.TimeLimit
if timeLimit == 0 { // if time limit is set to zero, the user wants to get the latest update
timeLimit = TimestampProvider.Now().Time
}
if query.Hint == lookup.NoClue { // try to use our cache
entry := h.get(&query.Feed)
if entry != nil && entry.Epoch.Time <= timeLimit { // avoid bad hints
query.Hint = entry.Epoch
}
}
// we can't look for anything without a store
if h.chunkStore == nil {
return nil, NewError(ErrInit, "Call Handler.SetStore() before performing lookups")
}
var id ID
id.Feed = query.Feed
var readCount int
// Invoke the lookup engine.
// The callback will be called every time the lookup algorithm needs to guess
requestPtr, err := lookup.Lookup(timeLimit, query.Hint, func(epoch lookup.Epoch, now uint64) (interface{}, error) {
readCount++
id.Epoch = epoch
ctx, cancel := context.WithTimeout(ctx, defaultRetrieveTimeout)
defer cancel()
chunk, err := h.chunkStore.Get(ctx, id.Addr())
if err != nil { // TODO: check for catastrophic errors other than chunk not found
return nil, nil
}
var request Request
if err := request.fromChunk(chunk.Address(), chunk.Data()); err != nil {
return nil, nil
}
if request.Time <= timeLimit {
return &request, nil
}
return nil, nil
})
if err != nil {
return nil, err
}
log.Info(fmt.Sprintf("Feed lookup finished in %d lookups", readCount))
request, _ := requestPtr.(*Request)
if request == nil {
return nil, NewError(ErrNotFound, "no feed updates found")
}
return h.updateCache(request)
}
// update feed updates cache with specified content
func (h *Handler) updateCache(request *Request) (*cacheEntry, error) {
updateAddr := request.Addr()
log.Trace("feed cache update", "topic", request.Topic.Hex(), "updateaddr", updateAddr, "epoch time", request.Epoch.Time, "epoch level", request.Epoch.Level)
feedUpdate := h.get(&request.Feed)
if feedUpdate == nil {
feedUpdate = &cacheEntry{}
h.set(&request.Feed, feedUpdate)
}
// update our rsrcs entry map
feedUpdate.lastKey = updateAddr
feedUpdate.Update = request.Update
feedUpdate.Reader = bytes.NewReader(feedUpdate.data)
return feedUpdate, nil
}
// Update publishes a feed update
// Note that a Feed update cannot span chunks, and thus has a MAX NET LENGTH 4096, INCLUDING update header data and signature.
// This results in a max payload of `maxUpdateDataLength` (check update.go for more details)
// An error will be returned if the total length of the chunk payload will exceed this limit.
// Update can only check if the caller is trying to overwrite the very last known version, otherwise it just puts the update
// on the network.
func (h *Handler) Update(ctx context.Context, r *Request) (updateAddr storage.Address, err error) {
// we can't update anything without a store
if h.chunkStore == nil {
return nil, NewError(ErrInit, "Call Handler.SetStore() before updating")
}
feedUpdate := h.get(&r.Feed)
if feedUpdate != nil && feedUpdate.Epoch.Equals(r.Epoch) { // This is the only cheap check we can do for sure
return nil, NewError(ErrInvalidValue, "A former update in this epoch is already known to exist")
}
chunk, err := r.toChunk() // Serialize the update into a chunk. Fails if data is too big
if err != nil {
return nil, err
}
// send the chunk
h.chunkStore.Put(ctx, chunk)
log.Trace("feed update", "updateAddr", r.idAddr, "epoch time", r.Epoch.Time, "epoch level", r.Epoch.Level, "data", chunk.Data())
// update our resources map cache entry if the new update is older than the one we have, if we have it.
if feedUpdate != nil && r.Epoch.After(feedUpdate.Epoch) {
feedUpdate.Epoch = r.Epoch
feedUpdate.data = make([]byte, len(r.data))
feedUpdate.lastKey = r.idAddr
copy(feedUpdate.data, r.data)
feedUpdate.Reader = bytes.NewReader(feedUpdate.data)
}
return r.idAddr, nil
}
// Retrieves the feed update cache value for the given nameHash
func (h *Handler) get(feed *Feed) *cacheEntry {
mapKey := feed.mapKey()
h.cacheLock.RLock()
defer h.cacheLock.RUnlock()
feedUpdate := h.cache[mapKey]
return feedUpdate
}
// Sets the feed update cache value for the given Feed
func (h *Handler) set(feed *Feed, feedUpdate *cacheEntry) {
mapKey := feed.mapKey()
h.cacheLock.Lock()
defer h.cacheLock.Unlock()
h.cache[mapKey] = feedUpdate
}
