WebSocket is cool, and you probably already played with it. But it’s just a transport technology. If you have thousands of client connections you need to do lots of improvements to make it scalable, reliable and achieve high performance. You need to implement many things on top of it. We are building financial data streaming platform for thousands of traders using WebSocket. I’m going to share my experience and cover such techniques as delta delivery, conflation, dynamic throttling, bandwidth and frequency limitation and other. I will also do a live demo of how to build scalable WebSocket backend from scratch using Java and Spring.

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VOXXED DAYS MINSK 2018
BUILDING SCALABLE
WEBSOCKET BACKEND
KONSTANTIN SLISENKO
LEAD SOFTWARE ENGINEER
MAY 26, 2018

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kslisenko@gmail.com
Konstantin Slisenko
• Java Team Lead at EPAM
• I’m building trading software
• 8+ years with Java
• 3+ years with WebSocket
github.com/kslisenko

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WHAT IS WEBSOCKET
standard: tools.ietf.org/html/rfc6455

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HTTP
WHAT IS WEBSOCKET
GET /demo HTTP/1.1
Upgrade: WebSocket
Connection: Upgrade
standard: tools.ietf.org/html/rfc6455

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HTTP
WHAT IS WEBSOCKET
HTTP/1.1 101 Web Socket Protocol Handshake
Upgrade: WebSocket
Connection: Upgrade
GET /demo HTTP/1.1
Upgrade: WebSocket
Connection: Upgrade
standard: tools.ietf.org/html/rfc6455

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TCP
HTTP
WHAT IS WEBSOCKET
HTTP/1.1 101 Web Socket Protocol Handshake
Upgrade: WebSocket
Connection: Upgrade
GET /demo HTTP/1.1
Upgrade: WebSocket
Connection: Upgrade
DATA DATA DATA DATA DATA
DATA DATA DATA DATA DATA
standard: tools.ietf.org/html/rfc6455

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• Permanent connection
WEBSOCKET PROVIDES

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• Permanent connection
• Bidirectional communication
WEBSOCKET PROVIDES

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• Permanent connection
• Bidirectional communication
• Sending text or binary data
WEBSOCKET PROVIDES

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• Permanent connection
• Bidirectional communication
• Sending text or binary data
• Guaranteed delivery (TCP/IP)
WEBSOCKET PROVIDES

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• API and application protocol
WEBSOCKET DOESN’T PROVIDE

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• API and application protocol
• Network failure handling*
WEBSOCKET DOESN’T PROVIDE
*Only basic handling

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• API and application protocol
• Network failure handling*
• Network slowness handling*
WEBSOCKET DOESN’T PROVIDE
*Only basic handling

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• API and application protocol
• Network failure handling*
• Network slowness handling*
• Bandwidth/frequency limitation
WEBSOCKET DOESN’T PROVIDE
*Only basic handling

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ONE DOES NOT SIMPLY
BUILD HIGH PERFORMANCE APPLICATION
USING ONLY STANDARD WEBSOCKET FEATURES

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High performance WebSocket backend
Basic WebSocket backend

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BACKEND
BASIC WEBSOCKET

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data
subscribe
WebSocket
data
subscribe
WebSocket

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data
subscribe
WebSocket
data
subscribe
WebSocket
any
protocol
data
subscribe

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data
subscribe
WebSocket
any
protocol
data
data
subscribe
WebSocket
subscribe
IBM
AAPL
IBM
AAPL

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AAPL
data
subscribe
WebSocket
AAPL
IBM
any
protocol
data
IBM
EPAM
data
subscribe
WebSocket
subscribe
IBM
TSLA

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BACKEND
BASIC WEBSOCKET
LIVE DEMO

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TOO MUCH DATA?
SEND LESS DATA!

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High performance WebSocket backend
Max frequency limit
Basic WebSocket backend

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HOW DO WE
SEND LESS DATA?

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RESAMPLING
No limits (10 updates/s)

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RESAMPLING
No limits (10 updates/s)
2 updates/s

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No limits (10 updates/s)
200 300 400 500 700 900
2 updates/s (last available)
900 1000600
600
100
100
RESAMPLING + CONFLATION

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No limits (10 updates/s)
100 200 300 400 500 600 700 800
2 updates/s (average)
300
900 1000
RESAMPLING + CONFLATION
800
100 + 200 + 300 + 400 + 500
5
= 300
600 + 700 + 800 + 900 + 1000
5
= 800

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data
data
subscribe
data
subscribe
subscribe
AAPL
IBM
IBM
TSLA
WebSocket
WebSocket
any
protocol
RECEIVINGTHREAD(S)

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data
data
subscribe
data
subscribe
subscribe
AAPL
IBM
IBM
TSLA
WebSocket
WebSocket
any
protocol
SHAREDMEMORY
RECEIVINGTHREAD(S)

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data
data
subscribe
data
subscribe
subscribe
AAPL
IBM
IBM
TSLA
WebSocket
WebSocket
SENDINGTHREAD(S)
any
protocol
SHAREDMEMORY
RECEIVINGTHREAD(S)

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data
data
subscribe
data
subscribe
subscribeAAPL
IBM
IBM
TSLA
TSLA
data
IBM
data
AAPL
data

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data
data
subscribe
data
subscribe
subscribeAAPL
IBM
IBM
TSLA
TSLA
data
info
info
info
info
rate limit
rate limit
rate limit
rate limit
IBM
data
AAPL
data

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WEBSOCKET
FREQUENCY LIMIT
LIVE DEMO

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MAX FREQUENCY LIMIT
2 KB/s*
Max frequency limit
33 KB/s*
No limits
-95%
* for demo application including gzip compression

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WHAT ELSE, CAP?

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WHAT ELSE, CAP?
SEND EVEN LESS DATA!

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High performance WebSocket backend
Schema
Max frequency limit
Basic WebSocket backend

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AAPL
snapshot
BID=10
ASK=15
LAST=12
BID SIZE=20
ASK SIZE=30
SCHEMA

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AAPL
snapshot
BID=10
schema
ASK=15
LAST=12
BID SIZE=20
ASK SIZE=30
BID=10
ASK=15
SCHEMA
BID
ASK

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AAPL
snapshot
BID=10
schema
ASK=15
LAST=12
BID SIZE=20
ASK SIZE=30
BID=10
ASK=15
BID=10
ASK=15
LAST=12
BID SIZE=20
ASK SIZE=30
SCHEMA
BID
ASK
schema
*

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High performance WebSocket backend
Max frequency limit
Basic WebSocket backend
Delta delivery
Schema

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DELTA DELIVERY
BID=10
ASK=15
LAST=12
BID SIZE=20
ASK SIZE=30
BID=15
ASK=15
LAST=12
BID SIZE=20
ASK SIZE=30
BID=20
ASK=20
LAST=12
BID SIZE=20
ASK SIZE=30
BID=20
ASK=20
LAST=12
BID SIZE=50
ASK SIZE=30
message message message message

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DELTA DELIVERY
BID=10
ASK=15
LAST=12
BID SIZE=20
ASK SIZE=30
BID=15
ASK=15
LAST=12
BID SIZE=20
ASK SIZE=30
BID=20
ASK=20
LAST=12
BID SIZE=20
ASK SIZE=30
BID=20
ASK=20
LAST=12
BID SIZE=50
ASK SIZE=30
message message message message

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DELTA DELIVERY
BID=10
ASK=15
LAST=12
BID SIZE=20
ASK SIZE=30
BID=15
ASK=15
LAST=12
BID SIZE=20
ASK SIZE=30
BID=20
ASK=20
LAST=12
BID SIZE=20
ASK SIZE=30
BID=20
ASK=20
LAST=12
BID SIZE=50
ASK SIZE=30
message message message message
BID=10
ASK=15
LAST=12
BID SIZE=20
ASK SIZE=30 BID=15
BID=20
ASK=20 BID SIZE=50
snapshot update update update

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High performance WebSocket backend
Delta delivery
Schema
Max frequency limit
Basic WebSocket backend
Position-based protocol

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{
symbol: AAPL,
bid: 10,
ask: 12,
last: 11,
bidSize: 100,
askSize: 200
}
AAPL|10|12|11|100|200
? bytes ? bytes

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{
symbol: AAPL,
bid: 10,
ask: 12,
last: 11,
bidSize: 100,
askSize: 200
}
AAPL|10|12|11|100|200
85 bytes 21 bytes

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{
symbol: AAPL,
bid: 10,
ask: 12,
last: 11,
bidSize: 100,
askSize: 200
}
AAPL||12|||200
46 bytes 14 bytes

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BANDWIDTH
OPTIMIZATION
LIVE DEMO

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SCHEMA + DELTA DELIVERY + POSITION-BASED PROTOCOL
400 B/s*
Using schema
2 KB/s*
No schema
-80%
* for demo application including gzip compression
370 B/s*
Delta delivery
-8%
310 B/s*
Position-based
-15%

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GOOD JOB!

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High performance WebSocket backend
Position-based protocol
Delta delivery
Schema
Max frequency limit
Basic WebSocket backend
Dynamic bandwidth control

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DYNAMIC BANDWIDTH CONTROL

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DYNAMIC BANDWIDTH CONTROL
Data

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DYNAMIC BANDWIDTH CONTROL
Data

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DYNAMIC BANDWIDTH CONTROL
DataData

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DYNAMIC BANDWIDTH CONTROL
DataData
Data Data
ACK ACK ACK ACK ACK

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DYNAMIC
LIVE DEMO
BANDWIDTH CONTROL

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DYNAMIC BANDWIDTH CONTROL
420 B/s*
Bandwidth control
310 B/s*
No control
+35%
* for demo application including gzip compression

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ARE WE READY
FOR PRODUCTION?

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http://lightstreamer.com

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LIGHTSTREAMER SERVER

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LIGHTSTREAMER SERVER
Data
adapter

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LIGHTSTREAMER SERVER
Data
adapter
Metadata
adapter

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CONCLUSION

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No improvements
2 KB/s*Max frequency limit
400 B/s*Schema
370 B/s*Delta delivery
310 B/s*Position-based
420 B/s*Bandwidth control
-95%
-80%
-8%
-15%
+35%
33 KB/s*
* for demo application including gzip compression
BANDWIDTH OPTIMIZATION*

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READ
High Performance Browser Networking
What every web developer should know
about networking and web performance
Free reading: https://hpbn.co/
By Ilya Grigorik
Publisher: O'Reilly Media
Release Date: September 2013

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http://lightstreamer.com/docs

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More Than Just WebSockets for Real-Time
Multiplayer Games and Collaboration
On YouTube and Slideshare
By Alessandro Alinone (CEO of Lightstreamer)

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1. Improve user-experience
2. Reduce bandwidth
3. Handle network failures
TAKE AWAYS

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QUESTIONS?
THANK YOU!

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github.com/kslisenko/streaming