1. Scalable Cross Language Services Implementation
Thrift
Scalable Cross Language Services Implementation
Sanjoy Singh
Senior Team Lead
Talentica S/W (I)
Pvt Ltd

2. Scalability ?? Design/Program is said to scale …
- if it is suitably efficient and practical when applied to large situations
Measures
Load
Functional

3. 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

4. LAMP Services
High-Level Goal: Enable transparent interaction between these.
…and some others too.

5. High Level Goals !
Transparent Interaction between multiple programming languages.
Maintain Right balance between
Performance
Ease and speed of development
Availability of existing libraries. etc

6. Simple Distributed Architecture
Sending requests, getting results
Waiting for requests
(known location,
known port)
Communication protocol, Data format
Basic questions are:
What kind of protocol to use, and what data to transmit
What to do with requests on the server side

7. Key Components/Challenges !
Type system
Transport system
Protocol system
Versioning
Processor
Performance
No problem can stand the assault of sustained thinking.

8. Hasn’t this been done before? (yes.)‏
SOAP
CORBA
COM
Pillar
Protocol Buffers etc

9. 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

10. Decision Time ! As a developer, what are you looking for?
Be Patient, I have something for you in the subsequent slides !!

11. Solution Apache Thrift
Software framework for scalable cross-language services development.

12. 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

13. Lets Dive It..

14. Principle Of Operation
Define Data types and Service interfaces
Create a thrift file
eg demo.thrift
Build Thrift platform files
Thrift Code Generator Tool
(written in C++)
Demo.php
Demo.cpp
Demo.py
Demo.java
First of all, in *.thrift file you declare objects and procedures, that you would like to interchange between applications written in different languages.
Then, using thrift tool, you build Thrift platform files for programming languages of your choice.
Most important step is to create server and client applications, using code generated in the previous step.
Server application should implement procedures declared in the thrift file, while client should call them.
Thrift itself takes care about creating transport classes, defining objects, etc. so your responsibility is only to use them in your code.
Last, but not least :) is to run your server. Then, using client script, you can perform actions using previously defined objects and methods.
Server implements Services and Client calls them
Create Server/Client App
Run the Server

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

16. 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,

17. 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()

18. 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()

19. 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

20. 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

21. 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.

22. 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?

23. 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.

24. The Thrift Stack Object write() Object read() Information Flow!
TProtocol
TTransport
TTransport
TProtocol

25. 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, }

26. Versioning - Case Analysis
Add a Field
New Client, Old Server
Server sees a field id that it doesn’t recognize, and safely ignores it.
Old Client, New Server
Server doesn’t see the field id it expects. Leaves it unset in object, server implementation can properly handle
Remove a Field
Server doesn’t see field it expects. Analogous to above.
Old client sends deprecated field. Server politely ignore it. Analogous to the top case.

27. 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

28. 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.

29. 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.

30. 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.

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

32. Some Real Time Example Facebook Search Service
AdServer, Blogfeeds, CSSParser, Memcached, Network Selector, News Feed, Scribe etc
Search Service
(implemented in C++
PHP based
Web App
Thrift PHP Lib

33. Why Should I not try this?
Guess the answer?
Answer: Please do let me know at
Skpe_id/Gtalk_id : sanjoy_17 /sanjoy17

34. References http://incubator.apache.org/thrift/
/thrift pdf

35. Thanks !!!