Merge pull request #152 from Arceliar/backpressure

Limit backpressure resource consumption
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Arceliar 2018-07-06 17:38:28 -05:00 committed by GitHub
commit adc21baa28
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@ -12,6 +12,7 @@ package yggdrasil
// A little annoying to do with constant changes from backpressure
import (
"math/rand"
"sync"
"sync/atomic"
"time"
@ -595,55 +596,88 @@ type switch_packetInfo struct {
// Used to keep track of buffered packets
type switch_buffer struct {
packets []switch_packetInfo // Currently buffered packets, which may be dropped if it grows too large
count uint64 // Total queue size, including dropped packets
size uint64 // Total queue size in bytes
}
func (b *switch_buffer) dropTimedOut() {
// TODO figure out what timeout makes sense
const timeout = 25 * time.Millisecond
now := time.Now()
for len(b.packets) > 0 && now.Sub(b.packets[0].time) > timeout {
util_putBytes(b.packets[0].bytes)
b.packets = b.packets[1:]
type switch_buffers struct {
bufs map[string]switch_buffer // Buffers indexed by StreamID
size uint64 // Total size of all buffers, in bytes
}
func (b *switch_buffers) cleanup(t *switchTable) {
for streamID, buf := range b.bufs {
// Remove queues for which we have no next hop
packet := buf.packets[0]
coords := switch_getPacketCoords(packet.bytes)
if t.selfIsClosest(coords) {
for _, packet := range buf.packets {
util_putBytes(packet.bytes)
}
b.size -= buf.size
delete(b.bufs, streamID)
}
}
const maxSize = 4 * 1048576 // Maximum 4 MB
for b.size > maxSize {
// Drop a random queue
target := rand.Uint64() % b.size
var size uint64 // running total
for streamID, buf := range b.bufs {
size += buf.size
if size < target {
continue
}
var packet switch_packetInfo
packet, buf.packets = buf.packets[0], buf.packets[1:]
buf.size -= uint64(len(packet.bytes))
b.size -= uint64(len(packet.bytes))
util_putBytes(packet.bytes)
if len(buf.packets) == 0 {
delete(b.bufs, streamID)
} else {
// Need to update the map, since buf was retrieved by value
b.bufs[streamID] = buf
}
break
}
}
}
// Handles incoming idle notifications
// Loops over packets and sends the newest one that's OK for this peer to send
// Returns true if the peer is no longer idle, false if it should be added to the idle list
func (t *switchTable) handleIdle(port switchPort, buffs map[string]switch_buffer) bool {
func (t *switchTable) handleIdle(port switchPort, bufs *switch_buffers) bool {
to := t.core.peers.getPorts()[port]
if to == nil {
return true
}
var best string
var bestSize uint64
for streamID, buf := range buffs {
var bestPriority float64
bufs.cleanup(t)
now := time.Now()
for streamID, buf := range bufs.bufs {
// Filter over the streams that this node is closer to
// Keep the one with the smallest queue
buf.dropTimedOut()
if len(buf.packets) == 0 {
delete(buffs, streamID)
continue
}
buffs[streamID] = buf
packet := buf.packets[0]
coords := switch_getPacketCoords(packet.bytes)
if (bestSize == 0 || buf.count < bestSize) && t.portIsCloser(coords, port) {
priority := float64(now.Sub(packet.time)) / float64(buf.size)
if priority > bestPriority && t.portIsCloser(coords, port) {
best = streamID
bestSize = buf.count
bestPriority = priority
}
}
if bestSize != 0 {
buf := buffs[best]
if bestPriority != 0 {
buf := bufs.bufs[best]
var packet switch_packetInfo
// TODO decide if this should be LIFO or FIFO
packet, buf.packets = buf.packets[0], buf.packets[1:]
buf.count--
buf.size -= uint64(len(packet.bytes))
bufs.size -= uint64(len(packet.bytes))
if len(buf.packets) == 0 {
delete(buffs, best)
delete(bufs.bufs, best)
} else {
buffs[best] = buf
// Need to update the map, since buf was retrieved by value
bufs.bufs[best] = buf
}
to.sendPacket(packet.bytes)
return true
@ -654,25 +688,27 @@ func (t *switchTable) handleIdle(port switchPort, buffs map[string]switch_buffer
// The switch worker does routing lookups and sends packets to where they need to be
func (t *switchTable) doWorker() {
buffs := make(map[string]switch_buffer) // Packets per PacketStreamID (string)
var bufs switch_buffers
bufs.bufs = make(map[string]switch_buffer) // Packets per PacketStreamID (string)
idle := make(map[switchPort]struct{}) // this is to deduplicate things
for {
select {
case packet := <-t.packetIn:
case bytes := <-t.packetIn:
// Try to send it somewhere (or drop it if it's corrupt or at a dead end)
if !t.handleIn(packet, idle) {
if !t.handleIn(bytes, idle) {
// There's nobody free to take it right now, so queue it for later
streamID := switch_getPacketStreamID(packet)
buf := buffs[streamID]
buf.dropTimedOut()
pinfo := switch_packetInfo{packet, time.Now()}
buf.packets = append(buf.packets, pinfo)
buf.count++
buffs[streamID] = buf
packet := switch_packetInfo{bytes, time.Now()}
streamID := switch_getPacketStreamID(packet.bytes)
buf := bufs.bufs[streamID]
buf.packets = append(buf.packets, packet)
buf.size += uint64(len(packet.bytes))
bufs.size += uint64(len(packet.bytes))
bufs.bufs[streamID] = buf
bufs.cleanup(t)
}
case port := <-t.idleIn:
// Try to find something to send to this peer
if !t.handleIdle(port, buffs) {
if !t.handleIdle(port, &bufs) {
// Didn't find anything ready to send yet, so stay idle
idle[port] = struct{}{}
}