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Merge pull request #521 from ChIoT-Tech/master
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SetMaxResumePubInFlight option - limit inflight publish packets on resume
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MattBrittan committed Jul 19, 2021
2 parents 88d5334 + 1dc06fb commit 06f46aa
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Showing 5 changed files with 213 additions and 1 deletion.
39 changes: 38 additions & 1 deletion client.go
Expand Up @@ -19,6 +19,7 @@ package mqtt

import (
"bytes"
"context"
"errors"
"fmt"
"net"
Expand All @@ -27,6 +28,8 @@ import (
"sync/atomic"
"time"

"golang.org/x/sync/semaphore"

"github.com/eclipse/paho.mqtt.golang/packets"
)

Expand Down Expand Up @@ -919,10 +922,42 @@ func (c *client) reserveStoredPublishIDs() {
// Load all stored messages and resend them
// Call this to ensure QOS > 1,2 even after an application crash
// Note: This function will exit if c.stop is closed (this allows the shutdown to proceed avoiding a potential deadlock)
//
// other than that it does not return until all messages in the store have been sent (connect() does not complete its
// token before this completes)
func (c *client) resume(subscription bool, ibound chan packets.ControlPacket) {
DEBUG.Println(STR, "enter Resume")

// Prior to sending a message getSemaphore will be called and once sent releaseSemaphore will be called
// with the token (so semaphore can be released when ACK received if applicable).
// Using a weighted semaphore rather than channels because this retains ordering
getSemaphore := func() {} // Default = do nothing
releaseSemaphore := func(_ *PublishToken) {} // Default = do nothing
var sem *semaphore.Weighted
if c.options.MaxResumePubInFlight > 0 {
sem = semaphore.NewWeighted(int64(c.options.MaxResumePubInFlight))
ctx, cancel := context.WithCancel(context.Background()) // Context needed for semaphore
defer cancel() // ensure context gets cancelled

go func() {
select {
case <-c.stop: // Request to stop (due to comm error etc)
cancel()
case <-ctx.Done(): // resume completed normally
}
}()

getSemaphore = func() { sem.Acquire(ctx, 1) }
releaseSemaphore = func(token *PublishToken) { // Note: If token never completes then resume() may stall (will still exit on ctx.Done())
go func() {
select {
case <-token.Done():
case <-ctx.Done():
}
sem.Release(1)
}()
}
}

storedKeys := c.persist.All()
for _, key := range storedKeys {
packet := c.persist.Get(key)
Expand Down Expand Up @@ -986,12 +1021,14 @@ func (c *client) resume(subscription bool, ibound chan packets.ControlPacket) {
c.claimID(token, details.MessageID)
DEBUG.Println(STR, fmt.Sprintf("loaded pending publish (%d)", details.MessageID))
DEBUG.Println(STR, details)
getSemaphore()
select {
case c.obound <- &PacketAndToken{p: p, t: token}:
case <-c.stop:
DEBUG.Println(STR, "resume exiting due to stop")
return
}
releaseSemaphore(token) // If limiting simultaneous messages then we need to know when message is acknowledged
default:
ERROR.Println(STR, "invalid message type in store (discarded)")
c.persist.Del(key)
Expand Down
1 change: 1 addition & 0 deletions go.mod
Expand Up @@ -5,4 +5,5 @@ go 1.14
require (
github.com/gorilla/websocket v1.4.2
golang.org/x/net v0.0.0-20200425230154-ff2c4b7c35a0
golang.org/x/sync v0.0.0-20210220032951-036812b2e83c
)
2 changes: 2 additions & 0 deletions go.sum
Expand Up @@ -3,6 +3,8 @@ github.com/gorilla/websocket v1.4.2/go.mod h1:YR8l580nyteQvAITg2hZ9XVh4b55+EU/ad
golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
golang.org/x/net v0.0.0-20200425230154-ff2c4b7c35a0 h1:Jcxah/M+oLZ/R4/z5RzfPzGbPXnVDPkEDtf2JnuxN+U=
golang.org/x/net v0.0.0-20200425230154-ff2c4b7c35a0/go.mod h1:qpuaurCH72eLCgpAm/N6yyVIVM9cpaDIP3A8BGJEC5A=
golang.org/x/sync v0.0.0-20210220032951-036812b2e83c h1:5KslGYwFpkhGh+Q16bwMP3cOontH8FOep7tGV86Y7SQ=
golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
golang.org/x/sys v0.0.0-20200323222414-85ca7c5b95cd/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
161 changes: 161 additions & 0 deletions memstore_ordered.go
@@ -0,0 +1,161 @@
/*
* Copyright (c) 2013 IBM Corp.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Seth Hoenig
* Allan Stockdill-Mander
* Mike Robertson
*/

package mqtt

import (
"sort"
"sync"
"time"

"github.com/eclipse/paho.mqtt.golang/packets"
)

// OrderedMemoryStore uses a map internally so the order in which All() returns packets is
// undefined. OrderedMemoryStore resolves this by storing the time the message is added
// and sorting based upon this.

// storedMessage encapsulates a message and the time it was initially stored
type storedMessage struct {
ts time.Time
msg packets.ControlPacket
}

// OrderedMemoryStore implements the store interface to provide a "persistence"
// mechanism wholly stored in memory. This is only useful for
// as long as the client instance exists.
type OrderedMemoryStore struct {
sync.RWMutex
messages map[string]storedMessage
opened bool
}

// NewOrderedMemoryStore returns a pointer to a new instance of
// OrderedMemoryStore, the instance is not initialized and ready to
// use until Open() has been called on it.
func NewOrderedMemoryStore() *OrderedMemoryStore {
store := &OrderedMemoryStore{
messages: make(map[string]storedMessage),
opened: false,
}
return store
}

// Open initializes a OrderedMemoryStore instance.
func (store *OrderedMemoryStore) Open() {
store.Lock()
defer store.Unlock()
store.opened = true
DEBUG.Println(STR, "OrderedMemoryStore initialized")
}

// Put takes a key and a pointer to a Message and stores the
// message.
func (store *OrderedMemoryStore) Put(key string, message packets.ControlPacket) {
store.Lock()
defer store.Unlock()
if !store.opened {
ERROR.Println(STR, "Trying to use memory store, but not open")
return
}
store.messages[key] = storedMessage{ts: time.Now(), msg: message}
}

// Get takes a key and looks in the store for a matching Message
// returning either the Message pointer or nil.
func (store *OrderedMemoryStore) Get(key string) packets.ControlPacket {
store.RLock()
defer store.RUnlock()
if !store.opened {
ERROR.Println(STR, "Trying to use memory store, but not open")
return nil
}
mid := mIDFromKey(key)
m, ok := store.messages[key]
if !ok || m.msg == nil {
CRITICAL.Println(STR, "OrderedMemoryStore get: message", mid, "not found")
} else {
DEBUG.Println(STR, "OrderedMemoryStore get: message", mid, "found")
}
return m.msg
}

// All returns a slice of strings containing all the keys currently
// in the OrderedMemoryStore.
func (store *OrderedMemoryStore) All() []string {
store.RLock()
defer store.RUnlock()
if !store.opened {
ERROR.Println(STR, "Trying to use memory store, but not open")
return nil
}
type tsAndKey struct {
ts time.Time
key string
}

tsKeys := make([]tsAndKey, 0, len(store.messages))
for k, v := range store.messages {
tsKeys = append(tsKeys, tsAndKey{ts: v.ts, key: k})
}
sort.Slice(tsKeys, func(a int, b int) bool { return tsKeys[a].ts.Before(tsKeys[b].ts) })

keys := make([]string, len(tsKeys))
for i := range tsKeys {
keys[i] = tsKeys[i].key
}
return keys
}

// Del takes a key, searches the OrderedMemoryStore and if the key is found
// deletes the Message pointer associated with it.
func (store *OrderedMemoryStore) Del(key string) {
store.Lock()
defer store.Unlock()
if !store.opened {
ERROR.Println(STR, "Trying to use memory store, but not open")
return
}
mid := mIDFromKey(key)
_, ok := store.messages[key]
if !ok {
WARN.Println(STR, "OrderedMemoryStore del: message", mid, "not found")
} else {
delete(store.messages, key)
DEBUG.Println(STR, "OrderedMemoryStore del: message", mid, "was deleted")
}
}

// Close will disallow modifications to the state of the store.
func (store *OrderedMemoryStore) Close() {
store.Lock()
defer store.Unlock()
if !store.opened {
ERROR.Println(STR, "Trying to close memory store, but not open")
return
}
store.opened = false
DEBUG.Println(STR, "OrderedMemoryStore closed")
}

// Reset eliminates all persisted message data in the store.
func (store *OrderedMemoryStore) Reset() {
store.Lock()
defer store.Unlock()
if !store.opened {
ERROR.Println(STR, "Trying to reset memory store, but not open")
}
store.messages = make(map[string]storedMessage)
WARN.Println(STR, "OrderedMemoryStore wiped")
}
11 changes: 11 additions & 0 deletions options.go
Expand Up @@ -88,6 +88,7 @@ type ClientOptions struct {
ResumeSubs bool
HTTPHeaders http.Header
WebsocketOptions *WebsocketOptions
MaxResumePubInFlight int // // 0 = no limit; otherwise this is the maximum simultaneous messages sent while resuming
}

// NewClientOptions will create a new ClientClientOptions type with some
Expand Down Expand Up @@ -401,3 +402,13 @@ func (o *ClientOptions) SetWebsocketOptions(w *WebsocketOptions) *ClientOptions
o.WebsocketOptions = w
return o
}

// SetMaxResumePubInFlight sets the maximum simultaneous publish messages that will be sent while resuming. Note that
// this only applies to messages coming from the store (so additional sends may push us over the limit)
// Note that the connect token will not be flagged as complete until all messages have been sent from the
// store. If broker does not respond to messages then resume may not complete.
// This option was put in place because resuming after downtime can saturate low capacity links.
func (o *ClientOptions) SetMaxResumePubInFlight(MaxResumePubInFlight int) *ClientOptions {
o.MaxResumePubInFlight = MaxResumePubInFlight
return o
}

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