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ThriftScalable Cross Language Services Implementation

Sanjoy Singh Senior Team Lead

Talentica S/W (I) Pvt Ltd

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Scalability ??

Design/Program is said to scale …

- if it is suitably efficient and practical when applied to large situations

Measures

Load Functional

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Agenda Key Components/Challenges for Cross

Language Interactions Various System for Cross Language

Interactions Dive Into Apache Thrift

Principle Of Operation Example Thrift Stack Versioning

Why to use Thrift. Limitations? Quick Code Walkthrough

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LAMP + Services

High-Level Goal: Enable transparent interaction between these.

…and some others too.

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High Level Goals !

Transparent Interaction between multiple programming languages.

Maintain Right balance between Performance Ease and speed of development Availability of existing libraries. etc

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Simple Distributed Architecture

Communication protocol, Data format

Sending requests,

getting results

Sending requests,

getting results

Waiting for requests

(known location,

known port)

Waiting for requests

(known location,

known port)

Basic questions are:Basic questions are:

What kind of protocol to use, and what What kind of protocol to use, and what data to transmitdata to transmit

What to do with requests on the server What to do with requests on the server sideside

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Key Components/Challenges !

Type system Transport system Protocol system Versioning Processor Performance

No problem can stand the assault of sustained thinking.

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Hasn’t this been done before? (yes.)

SOAP

CORBA

COM

Pillar

Protocol Buffers etc

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Should we pick up one of those? (not sure)

SOAP XML, XML, and more XML

CORBA Over designed and Heavyweight

COM Embraced mainly in Windows Client Software

Pillar Slick! But no versioning/abstraction.

Protocol Buffers etc Closed source Google deliciousness

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As a developer, what are you looking for?

Be Patient, I have something for you in the subsequent slides !!

Decision Time !

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Solution

Apache Thrift

Software framework for scalable cross-language services development.

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Apache Thrift - Introduction

Originally developed at Facebook Open sourced in April 2007 Easy exchange of data Cross language serialization with

minimal overhead . Thrift tools can generate code for

C++, Java, Python, PHP, Ruby, Erlang, Perl, Haskell, C#, Cocoa, Smalltalk and OCaml

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Lets Dive It..

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Principle Of Operation

Thrift Code Generator Tool(written in C++)

Create a thrift fileeg demo.thrift

Define Data types and Service

interfaces

Build Thrift platform files

Demo.php Demo.javaDemo.pyDemo.cpp

Create Server/Client AppRun the Server

Server implements Services and Client calls

them

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Thrift Cares About Type Definitions Service Definitions

Thrift Doesn’t Care About Wire Protocol (internal XML...) Transport (HTTP? Sockets? Whatevz!) Programming Languages

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Enough Banter. Show Us the Goodz.// Include other thrift files

include "shared.thrift“

namespace java calculator

enum Operation { // define enums

ADD = 1,

SUBTRACT = 2,

MULTIPLY = 3,

DIVIDE = 4

}

struct Work {// complex data structures

1: i32 num1 = 0,

2: i32 num2,

3: Operation op,

4: optional string comment,

}

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Enough Banter. Show Us the Goodz.

// Exception

exception InvalidOperation {

1: i32 what,

2: string why

}

// Service

service Calculator extends shared.SharedService {

void ping(),

i32 add(1:i32 num1, 2:i32 num2),

i32 calculate(1:i32 logid, 2:Work w) throws (1:InvalidOperation ouch),

oneway void zip()

}

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Enough Banter. Show Us the Goodz.// Include other thrift files

include "shared.thrift“

namespace java calculator

enum Operation { // define enums

ADD = 1,

SUBTRACT = 2,

MULTIPLY = 3,

DIVIDE = 4

}

struct Work {// complex data structures

1: i32 num1 = 0,

2: i32 num2,

3: Operation op,

4: optional string comment,

}

// Exception

exception InvalidOperation {

1: i32 what,

2: string why

}

// Service

service Calculator extends shared.SharedService {

void ping(),

i32 add(1:i32 num1, 2:i32 num2),

i32 calculate(1:i32 logid, 2:Work w) throws (1:InvalidOperation ouch),

oneway void zip()

}

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What DOES that do?

Generates definitions for all the types in each language

Generates Client and Server interfaces for each language

What DOESNT that do? Anything to do with sockets Anything to do with serialization

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Magically Generated Files

gen-java/calculatordemo

Calculator.java

InvalidOperation.java

Operation.java

Work.java

gen-php/

Calculator.php

calculator_types

gen-py/

ttypes.py

Calculator.py

Calculator-remote

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Thrift Philosophy

Create a system that is abstracted in a systematic way, such that developers can easily extend it to suit their needs and function in custom environments.

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Structs don’t have any code to do with serialization or sockets, etc.

But they know how to read and write themselves… How does that work?

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The Thrift Stack The Thrift stack is a common class hierarchy implemented in each language

that abstracts out the tricky details of protocol encoding and network communication.

It provides a simple interface for generated code to use.

There are two key interfaces:

TTransport

De-coupled the transport layer from Code Generation Layer. Provides read() and write(), with a set of other helpers like open(), close(),

etc. Implementation - TSocket, TFileTransport, TBufferedTransport,

TFramedTransport, TMemoryBuffer. TProtocol

Separate Data Structure from Transport representation. Provides the ability to read and write various types of data, i.e. readI32(),

writeString(), etc. Supports Bi-directional sequenced messaging and encoding of base types,

container and struts.

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The Thrift Stack

Objectwrite()

TTransport

TProtocol TTransport TProtocol

Objectread()

Information Flow!

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Versioning (applications change a lot, not protocols!) What happens when definitions change?

Struct needs a new member Function needs a new argument

No Problem! We’ve got Field Identifiers!

Example:

struct Work {

1: i32 num1 = 0,

2: i32 num2,

3: Operation op,

4: optional string comment,

}

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Versioning - Case AnalysisAdd a Field

New Client, Old ServerServer sees a field id that it doesn’t recognize, and safely

ignores it.

Old Client, New ServerServer doesn’t see the field id it expects. Leaves it unset in

object, server implementation can properly handle

Remove a Field New Client, Old Server

Server doesn’t see field it expects. Analogous to above. Old Client, New Server

Old client sends deprecated field. Server politely ignore it. Analogous to the top case.

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Why to use Thrift … Less time wasted by individual developers

No duplicated networking and protocol code less time dealing with boilerplate stuff Write your client and server in about 5 minutes

Less maintenance One networking code base that needs maintenance Fix bugs once, rather than repeatedly in every server

Division of labour Work on high-performance servers separate from

applications Common toolkit

Code reuse and shared tools

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Why to use Thrift … Cross-language serialization with lower overhead

than alternatives such as SOAP due to use of binary format

A lean and clean library. No framework to code to. No XML configuration files.

The language bindings feel natural. For example Java uses ArrayList<String>. C++ uses std::vector<std::string>.

The application-level wire format and the serialization-level wire format are cleanly separated. They can be modified independently.

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Why to use Thrift …

The predefined serialization styles include: binary, HTTP-friendly and compact binary.

Soft versioning of the protocol.

No build dependencies or non-standard software. No mix of incompatible software licenses.

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Limitations / Non-Features

Is struct inheritance/polymorphism supported?

No, it isn’t Can I overload service methods?

Nope. Method names must be unique. Heterogeneous containers Not supported

Is there any enough documentation on Thrift development?

I think this is one weak area.

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Steps/Code Walkthrough(Lets build the example described earlier)

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Some Real Time Example

Facebook Search Service

AdServer, Blogfeeds, CSSParser, Memcached, Network Selector, News Feed, Scribe etc

PHP based Web App

Thrift PHP Lib Search Service(implemented in C++

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Why Should I not try this?

Guess the answer?

Answer: Please do let me know at sanjoys@talentica.com

Skpe_id/Gtalk_id : sanjoy_17 /sanjoy17

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References

http://incubator.apache.org/thrift/http://incubator.apache.org/thrift/stat

ic/thrift-20070401.pdf

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Thanks !!!