1. No category

Thrift
Scalable 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
4 too.
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
Waiting for
requests
(known location,
Communication protocol, Data format
known port)
Sending
requests,
getting
results
Basic questions are:
 What kind of protocol to use, and what data to
transmit

What to do with requests on the server side
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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?

SOAP

CORBA

COM

Pillar

Protocol Buffers etc
(yes.)
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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
 Closed
Buffers etc
source Google deliciousness
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Decision Time !
As a developer, what are you looking
for?
Be Patient, I have something for you in
the subsequent slides !!
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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
Define Data
types and
Service
interfaces
Create a thrift file
eg demo.thrift
Thrift Code Generator Tool
(written in C++)
Demo.php
Demo.cpp
Demo.py
Create Server/Client App
Run the Server
Build Thrift
platform files
Demo.java
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
// Exception
include "shared.thrift“
exception InvalidOperation {
namespace java calculator
1: i32 what,
enum Operation { // define enums
2: string why
ADD = 1,
}
SUBTRACT = 2,
MULTIPLY = 3,
// Service
DIVIDE = 4
service Calculator extends
shared.SharedService {
}
void ping(),
struct Work {// complex data structures
i32 add(1:i32 num1, 2:i32 num2),
1: i32 num1 = 0,
2: i32 num2,
i32 calculate(1:i32 logid, 2:Work w)
throws (1:InvalidOperation ouch),
3: Operation op,
oneway void zip()
4: optional string comment,
}
}
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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
Object
write()
TProtocol
Information Flow!
TTransport
TTransport
Object
read()
TProtocol
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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 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
 New
a Field
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



No duplicated networking and protocol code
less time dealing with boilerplate stuff
Write your client and server in about 5 minutes
 Less


time wasted by individual developers
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
PHP based
Web App
Thrift PHP Lib
Search Service
(implemented in C++
AdServer, Blogfeeds, CSSParser,
Memcached, Network Selector, News
Feed, Scribe etc

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Why Should I not try this?
Guess the answer?
Answer: Please do let me know at [email protected]
Skpe_id/Gtalk_id : sanjoy_17 /sanjoy17
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References

http://incubator.apache.org/thrift/
http://incubator.apache.org/thrift/static
/thrift-20070401.pdf
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Thanks !!!
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