TOPIC NAME

Software Architecture Fundamentals

Tung.Nguyen (tungnq@fsoft.com.vn)

Solution ArchitectJun-2014

Architecture Patterns

Open Discussion- Scalable System Design

- Facebook Architecture

Architecture Portfolios

Scalable System Design Principles

Quality Attributes

Availability

Performance

Reliability

Scalability

Manageability

Cost

Key Quality Attributes

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http://www.aosabook.org/en/distsys.html

"Scalability" is not equivalent to "Raw

Performance"

Understand environmental

workload conditions that the system is

design for

Understand who is your priority customers

Scale out and Not scale up

Keep your code modular and simple

Don't guess the bottleneck, Measure it

Plan for growth

What Should We Focus On?

4http://horicky.blogspot.com/2008/02/scalable-system-design.html

Techniques

Server Farm/Cluster

(real time access) Data

Partitioning

Map / Reduce (Batch Parallel

Processing)

Content Delivery Network

(Static Cache)

Cache Engine (Dynamic

Cache)

Resources Pool

Calculate an approximate

result

Filtering at the source

Asynchronous Processing

Common Techniques

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Architecture Portfolios

Scalable System Design Patterns

Load Balancer

•A dispatcher determines which worker instance will handle a request based on different policies.

Scatter and Gather

•A dispatcher multicasts requests to all workers in a pool. Each worker will compute a local result and send it back to the dispatcher, who will consolidate them into a single response and then send back to the client.

Result Cache

•A dispatcher will first lookup if the request has been made before and try to find the previous result to return, in order to save the actual execution.

Shared Space

•All workers monitors information from the shared space and contributes partial knowledge back to the blackboard. The information is continuously enriched until a solution is reached.

Pipe and Filter

•All workers connected by pipes across which data flows.

MapReduce

•Targets batch jobs where disk I/O is the major bottleneck. It use a distributed file system so that disk I/O can be done in parallel.

Bulk Synchronous Parallel

• A lock-step execution across all workers, coordinated by a master.

Execution Orchestrator

• An intelligent scheduler / orchestrator schedules ready-to-run tasks (based on a dependency graph) across a clusters of dumb workers.

8 Commonly Used Scalable

System Design Patterns

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Load Balancer (1)

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• There is a dispatcher that determines which worker instance will handle the request based on different policies.

• The application should best be "stateless" so any worker instance can handle the request.

Load Balancer (2)

• Multi-Datacenter Architecture

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• 3-Tier Architecture

Rightscale: Cloud_Computing_System_Architecture_Diagrams

Load Balancer (3)

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• Multi-Tier Architecture with Memcached

Rightscale: Cloud_Computing_System_Architecture_Diagrams

Scatter and Gather

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• This pattern is used in Search engines like Yahoo, Google to handle user's keyword search request ... etc.

Result Cache

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The dispatcher will first lookup if the request has been made before and try to find the previous result to return, in order to save the actual execution.

Shared Space

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Pipe and Filter

14 It is a very common EAI pattern.

Map Reduce

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The model is targeting batch jobs where disk I/O is the major bottleneck. It

use a distributed file system so that disk I/O can be done in parallel.

Bulk Synchronous Parallel

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Execution Orchestrator

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Architecture Portfolios

Facebook Architecture

- Facebook Web Site

- Chat Service @ Facebook

- Big Data @ Facebook

Facebook Web Site

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• Users– More than 400 million active users. – 50% of active users login each day.– Average user has 130 friends on the site.

• Activity– User spends an average of 55 mins per day.– More than 60 million status updates each day.– More than 100 million photos uploaded each day.

• Platform– Currently 500K active applications.– About 250 apps have more than 1 million users.– About 60 million users use FB Connect from external

web sites each month.

Facebook Web SiteStatistic

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Challenges

• High Concurrency

• High Data Volumes

• Multilevel Hierarchical Data

Ok to Live with

• Not Mission Critical

• Cached data is fine

• Write Failures are tolerable

Facebook Web SiteTechnical Challenges

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• General Design Principles

– Use open source where possible

– Unix philosophy

• Keep individual components simple yet performant

• Combine as necessary

• Concentrate on clean interface points

– Build everything for scale

– Try to minimize failure points

– Simplicity, Simplicity, Simplicity.

Facebook Web SiteArchitecture

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Facebook Web SiteArchitecture

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Services Cache Database File System

Presentation Layer

Load Balancer

Web Servers runing PHP, basically

assembles data from lower layer

and presents it on the page.

Backend services are mainly

implemented in C++(other language can

be used). Very fast.

Memcached is used to cache almost

everything that is needed to produce a

page

An array of MySQL servers are used in

an interesting way to store the data

Internally developed file system,

Haystack used to store photos.

Facebook Web SiteArchitecture

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Facebook Web SiteTechnology Stack

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• Presentation Layer: PHP

• Issues:

– High CPU and memory consumption.

– An Interoperability with C++ Challenging.

– Language doesn’t encourage good programming in the large.

– Initialization cost of each page scales with size of code base

Facebook Web SiteWeb Tier at Facebook

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70

40

38

21

6

3

2

1

0 10 20 30 40 50 60 70 80

Ruby

PHP

Perl

Python

Erlang

C#

Java

C++

Relative Performance of Language Runtime (lower is better)

Programming Language performance ranking

• Optimizing PHP

– Op-code optimization

– APC improvements• Lazy loading

• Cache priming

– Custom extensions• Memcache client extension

• Serialization format

• Logging, Stats Collection, Monitoring

• Asynchronous event-handling mechanism

Facebook Web SiteWeb Tier at Facebook

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• HipHop

– Source Code Transformer

• Transform PHP in to highly optimized C++ and then compile it using g++

– 50% reduction in CPU usage than Apache + HTTP

– Facebook’s API tier can serve twice the traffic using 30% less CPU

– It has embedded simple webserver on top of libevent.

Facebook Web SiteWeb Tier at Facebook

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https://github.com/facebook/hhvm

• Tornado: Facebook's Real-Time Web Framework for Python– Tornado is a relatively simple, non-blocking Web server framework

written in Python

– It is designed to handle thousands of simultaneous connections, making it ideal for real-time Web services.

Facebook Web SiteWeb Tier at Facebook

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http://www.tornadoweb.org/

• BigPipe: first breaks web pages into multiple chunk called pagelets

Facebook Web SiteWeb Tier at Facebook

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• Memcached is an in-memory key-value store for small chunks of arbitrary data (strings, objects) from results of database calls, API calls, or page rendering.

• Alleviate database load

• Over 25TB in-memory caching on more than 800 servers

• Multi-gets used to make the system more efficient

• Facebook contributes UDP support and performance enhanced to Memcached.

Facebook Web SiteMemcached

31http://memcached.org/

• MySQL

– Fast and reliable

– Thousands of MySQL servers• Users randomly distributed across these servers

– Relational aspect of DB is not used• No joins. Logically difficult(Data is distributed randomly)

• Primarily key-value store

– Customizations• Custom partitioning scheme – Global id assigned to all data

• Custom archiving scheme – Base on frequency and recency of data on a per user basis

Facebook Web SiteMySQL Database

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Facebook Web SiteMemcached & MySQL at facebook

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• Many services written in C++, Python, Java

– AdServer

– Search

– Network Selector

– News Feed

– Blogfeeds

– CSSParser

– Mobile

– ShareScraper

Facebook Web SiteServices

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• Services Philosophy

– Create a service if required

• Real overhead for deployment, maintenance, separate code-base

• Another failure point

– Create a common framework and toolset that allow for easier creation of services

• Thrift

• Scribe

• ODS, Alerting, Monitoring service

– Use the right language

Facebook Web SiteServices

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• How to community between these?

• Thrift– http://incubator.apache.org/thrift/

– Lightweight software framework for cross-language development

– Provide IDL, statically generate code

– Supported bindings: C++, Java, Python, PHP, Ruby, Erlang, Perl, Haskell, C#, Cocoa, Smalltalk, and Ocaml

Facebook Web SiteServices

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Architecture Portfolios

Facebook Architecture

- Facebook Web Site

- Chat Service @ Facebook

- Big Data @ Facebook

• Statistic– Facebook has 200M active users– 800+ million user messages / day– 7+ million active channels at peak– 1GB+ in / sec at peak– 100+ channel machines

• System challenges– How does synchronous messaging work on the Web?

• "Presence" is hard to scale

– Need a system to queue and deliver messages– Millions of connections, mostly idle– Need logging, at least between page loads– Make it work in Facebook’s environment

Chat Service @ Facebook Statistic & Challenges

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Chat Service @ Facebook System Overview

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Chat Service @ Facebook System Overview

• User Interface– Mix of client-side Javascript

and server-side PHP

– Works around transport errors, browser differences

– Regular AJAX for sending messages, fetching conversation history

– Periodic AJAX polling for list of online friends

– AJAX long-polling for messages (Comet)

• Back End– Discrete responsibilities for each

service• Communicate via Thrift

– Channel (Erlang): message queuing and delivery• Queue messages in each user’s

“channel”

• Deliver messages as responses to long-polling HTTP requests

– Presence (C++): aggregates online info in memory (pull-based presence)

– Chatlogger (C++): stores conversations between page loads

– Web tier (PHP): serves our vanilla web requests

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Chat Service @ Facebook System Overview

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Chat Service @ Facebook Message Send

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Chat Service @ Facebook Channel Server

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Chat Service @ Facebook Channel Server

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• One channel per user

• Web tier delivers messages for that user

• Channel State: short queue of sequenced messages

• Long poll for streaming (Comet)

– Clients make an HTTP request

– Server replies when a message is ready

– One active request per browser tab

Architecture Portfolios

Facebook Architecture

- Facebook Web Site

- Chat Service @ Facebook

- Big Data @ Facebook

Big Data @ FacebookOverview

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Big Data @ FacebookData Infrastructure Overview

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Data Infrastructure @ FB built on open source technologies:

• Many committers across all the projects

• Plans to open source other parts of the data stack

• Figure out a model to stay in sync and still work at FB speed

Big Data @ FacebookLife of a tag for data infrastructure

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Big Data @ FacebookLife of a tag for data infrastructure

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• Technoloy:

– Log collection - Scribe

– Realtime analyitcs - Puma

– Batch analytics – Hive

– Adhoc analytics - Peregrine

– Periodic analytics - Nocron

Big Data @ FacebookWarehouse Architecture

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4TB of compressed new data added per day.

135TB of compressed data scanned per day.

7500+ Hive Job on production cluster per day.

80K computer hours per day.

• Scribe– http://developers.facebook.com/scribe/ – Scalable distributed logging framework– Useful for logging a wide array of data– Simple data model– Built on top of Thrift

• Hive– A system for managing and querying structure data built on top of

Hadoop.• Map Reduce for execution• HDFS for storage• Metadata in an RDBMS

– Key Building Principles:• SQL as a familiar data warehousing tool.• Extensibility – Type, Functions, Formats, Scripts.• Scalability and Performance• Interoperability.

Big Data @ FacebookWarehouse Architecture

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Big Data @ FacebookWarehouse Architecture

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• Hive Architecture

Big Data @ FacebookWarehouse Architecture

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• Data Flow Architecture

• Memcache at FB -https://www.facebook.com/video/video.php?v=631826881803

• http://www.gargasz.info/facebook-discovering-software-architecture/

• http://www.infoq.com/presentations/Facebook-Software-Stack

• http://www.infoq.com/presentations/Scale-at-Facebook

• http://www.slideshare.net/AditiTechnologies/facebook-architecture-breaking-it-open

• http://stackoverflow.com/questions/3533948/facebook-architecture

• http://www.quora.com/Facebook-Engineering/What-is-Facebooks-architecture

• http://www.slideshare.net/AditiTechnologies/google-architecture-breaking-it-open

Open Discussion !!!

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