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query.go
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query.go
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package dht
import (
"context"
"sync"
u "github.com/ipfs/go-ipfs-util"
logging "github.com/ipfs/go-log"
todoctr "github.com/ipfs/go-todocounter"
process "github.com/jbenet/goprocess"
ctxproc "github.com/jbenet/goprocess/context"
inet "github.com/libp2p/go-libp2p-net"
peer "github.com/libp2p/go-libp2p-peer"
pset "github.com/libp2p/go-libp2p-peer/peerset"
pstore "github.com/libp2p/go-libp2p-peerstore"
queue "github.com/libp2p/go-libp2p-peerstore/queue"
routing "github.com/libp2p/go-libp2p-routing"
notif "github.com/libp2p/go-libp2p-routing/notifications"
)
var maxQueryConcurrency = AlphaValue
type dhtQuery struct {
dht *IpfsDHT
key string // the key we're querying for
qfunc queryFunc // the function to execute per peer
concurrency int // the concurrency parameter
}
type dhtQueryResult struct {
value []byte // GetValue
peer *pstore.PeerInfo // FindPeer
providerPeers []pstore.PeerInfo // GetProviders
closerPeers []*pstore.PeerInfo // *
success bool
finalSet *pset.PeerSet
queriedSet *pset.PeerSet
}
// constructs query
func (dht *IpfsDHT) newQuery(k string, f queryFunc) *dhtQuery {
return &dhtQuery{
key: k,
dht: dht,
qfunc: f,
concurrency: maxQueryConcurrency,
}
}
// QueryFunc is a function that runs a particular query with a given peer.
// It returns either:
// - the value
// - a list of peers potentially better able to serve the query
// - an error
type queryFunc func(context.Context, peer.ID) (*dhtQueryResult, error)
// Run runs the query at hand. pass in a list of peers to use first.
func (q *dhtQuery) Run(ctx context.Context, peers []peer.ID) (*dhtQueryResult, error) {
select {
case <-ctx.Done():
return nil, ctx.Err()
default:
}
ctx, cancel := context.WithCancel(ctx)
defer cancel()
runner := newQueryRunner(q)
return runner.Run(ctx, peers)
}
type dhtQueryRunner struct {
query *dhtQuery // query to run
peersSeen *pset.PeerSet // all peers queried. prevent querying same peer 2x
peersQueried *pset.PeerSet // peers successfully connected to and queried
peersToQuery *queue.ChanQueue // peers remaining to be queried
peersRemaining todoctr.Counter // peersToQuery + currently processing
result *dhtQueryResult // query result
errs u.MultiErr // result errors. maybe should be a map[peer.ID]error
rateLimit chan struct{} // processing semaphore
log logging.EventLogger
runCtx context.Context
proc process.Process
sync.RWMutex
}
func newQueryRunner(q *dhtQuery) *dhtQueryRunner {
proc := process.WithParent(process.Background())
ctx := ctxproc.OnClosingContext(proc)
return &dhtQueryRunner{
query: q,
peersToQuery: queue.NewChanQueue(ctx, queue.NewXORDistancePQ(string(q.key))),
peersRemaining: todoctr.NewSyncCounter(),
peersSeen: pset.New(),
peersQueried: pset.New(),
rateLimit: make(chan struct{}, q.concurrency),
proc: proc,
}
}
func (r *dhtQueryRunner) Run(ctx context.Context, peers []peer.ID) (*dhtQueryResult, error) {
r.log = log
r.runCtx = ctx
if len(peers) == 0 {
log.Warning("Running query with no peers!")
return nil, nil
}
// setup concurrency rate limiting
for i := 0; i < r.query.concurrency; i++ {
r.rateLimit <- struct{}{}
}
// add all the peers we got first.
for _, p := range peers {
r.addPeerToQuery(p)
}
// go do this thing.
// do it as a child proc to make sure Run exits
// ONLY AFTER spawn workers has exited.
r.proc.Go(r.spawnWorkers)
// so workers are working.
// wait until they're done.
err := routing.ErrNotFound
// now, if the context finishes, close the proc.
// we have to do it here because the logic before is setup, which
// should run without closing the proc.
ctxproc.CloseAfterContext(r.proc, ctx)
select {
case <-r.peersRemaining.Done():
r.proc.Close()
r.RLock()
defer r.RUnlock()
err = routing.ErrNotFound
// if every query to every peer failed, something must be very wrong.
if len(r.errs) > 0 && len(r.errs) == r.peersSeen.Size() {
log.Debugf("query errs: %s", r.errs)
err = r.errs[0]
}
case <-r.proc.Closed():
r.RLock()
defer r.RUnlock()
err = context.DeadlineExceeded
}
if r.result != nil && r.result.success {
return r.result, nil
}
return &dhtQueryResult{
finalSet: r.peersSeen,
queriedSet: r.peersQueried,
}, err
}
func (r *dhtQueryRunner) addPeerToQuery(next peer.ID) {
// if new peer is ourselves...
if next == r.query.dht.self {
r.log.Debug("addPeerToQuery skip self")
return
}
if !r.peersSeen.TryAdd(next) {
return
}
notif.PublishQueryEvent(r.runCtx, ¬if.QueryEvent{
Type: notif.AddingPeer,
ID: next,
})
r.peersRemaining.Increment(1)
select {
case r.peersToQuery.EnqChan <- next:
case <-r.proc.Closing():
}
}
func (r *dhtQueryRunner) spawnWorkers(proc process.Process) {
for {
select {
case <-r.peersRemaining.Done():
return
case <-r.proc.Closing():
return
case <-r.rateLimit:
select {
case p, more := <-r.peersToQuery.DeqChan:
if !more {
// Put this back so we can finish any outstanding queries.
r.rateLimit <- struct{}{}
return // channel closed.
}
// do it as a child func to make sure Run exits
// ONLY AFTER spawn workers has exited.
proc.Go(func(proc process.Process) {
r.queryPeer(proc, p)
})
case <-r.proc.Closing():
return
case <-r.peersRemaining.Done():
return
}
}
}
}
func (r *dhtQueryRunner) queryPeer(proc process.Process, p peer.ID) {
// ok let's do this!
// create a context from our proc.
ctx := ctxproc.OnClosingContext(proc)
// make sure we do this when we exit
defer func() {
// signal we're done processing peer p
r.peersRemaining.Decrement(1)
r.rateLimit <- struct{}{}
}()
// make sure we're connected to the peer.
// FIXME abstract away into the network layer
// Note: Failure to connect in this block will cause the function to
// short circuit.
if r.query.dht.host.Network().Connectedness(p) == inet.NotConnected {
log.Debug("not connected. dialing.")
notif.PublishQueryEvent(r.runCtx, ¬if.QueryEvent{
Type: notif.DialingPeer,
ID: p,
})
// while we dial, we do not take up a rate limit. this is to allow
// forward progress during potentially very high latency dials.
r.rateLimit <- struct{}{}
pi := pstore.PeerInfo{ID: p}
if err := r.query.dht.host.Connect(ctx, pi); err != nil {
log.Debugf("Error connecting: %s", err)
notif.PublishQueryEvent(r.runCtx, ¬if.QueryEvent{
Type: notif.QueryError,
Extra: err.Error(),
ID: p,
})
r.Lock()
r.errs = append(r.errs, err)
r.Unlock()
<-r.rateLimit // need to grab it again, as we deferred.
return
}
<-r.rateLimit // need to grab it again, as we deferred.
log.Debugf("connected. dial success.")
}
// finally, run the query against this peer
res, err := r.query.qfunc(ctx, p)
r.peersQueried.Add(p)
if err != nil {
log.Debugf("ERROR worker for: %v %v", p, err)
r.Lock()
r.errs = append(r.errs, err)
r.Unlock()
} else if res.success {
log.Debugf("SUCCESS worker for: %v %s", p, res)
r.Lock()
r.result = res
r.Unlock()
go r.proc.Close() // signal to everyone that we're done.
// must be async, as we're one of the children, and Close blocks.
} else if len(res.closerPeers) > 0 {
log.Debugf("PEERS CLOSER -- worker for: %v (%d closer peers)", p, len(res.closerPeers))
for _, next := range res.closerPeers {
if next.ID == r.query.dht.self { // don't add self.
log.Debugf("PEERS CLOSER -- worker for: %v found self", p)
continue
}
// add their addresses to the dialer's peerstore
r.query.dht.peerstore.AddAddrs(next.ID, next.Addrs, pstore.TempAddrTTL)
r.addPeerToQuery(next.ID)
log.Debugf("PEERS CLOSER -- worker for: %v added %v (%v)", p, next.ID, next.Addrs)
}
} else {
log.Debugf("QUERY worker for: %v - not found, and no closer peers.", p)
}
}