Mina in Real Life ASEU-2009

7/31/2019 Mina in Real Life ASEU-2009

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Schedule

Introduction to MINA S imple Us e Ca s e s

A more complex Use Case

Do's and Don'ts

Summary

Q&A


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The Business part

public class EchoProtocolHandler extends IoHandlerAdapter {

/**

* This is where we handle incoming messages

*/

public void m e s s a g e R e c e i v e d (IoSe ss ion se ss ion, Object mes sa ge)

throws Exception {

// Write the received data back to remote peer

s es s ion .write(((IoBuffer) me s s ag e).du plica te());

}

}


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Key concepts


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How it works...


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S imple us e ca s e s


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A Simple TCP server : EchoServer Based on TCP

Multi-Users

Should be fast

Returns what the users sent without

modification

Ok, let's code it !


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The echo server


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The Business part

public class EchoProtocolHandler extends IoHandlerAdapter {

/**

* This is where we handle incoming messages

*/

public void m e s s a g e R e c e i v e d (IoSe ss ion se ss ion, Object mes sa ge)

throws Exception {

// Write the received data back to remote peer

s es s ion .write(((IoBuffer) me s s ag e).du plica te());

}

}


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And that's it !

We ha ve cre a te d a S ocke tAcce ptor Then we associated a handler to it

And accepted incoming connections

Last, we implemented the logic in the

Handler, in the messageReceived()

method.


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What do we have ?

A multithreaded server Accepting many parallel clients

Roughly 4 lines of code !

We ca n e xte nde d the s e rve r e a s ily

For instance, adding a logger

Handling more messages

Or adding SSL support


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Adding a logging filter

public static void main(String[] args) throws Exception {


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Another simple Use Case

NTP Server UDP (port 123)

Fixed Message size

Binary protocol

Stateless

The code...


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A more complex

us e ca s e


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A more complex Use Case

Apache Directory Server TCP and UDP

Simple or Two levels protocols

Bina ry me s s a ge s Multiple handlers

Potentially hundred of thousands

connections Has to be fast


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Handle many protocols

LDAP (TCP) Kerberos (TCP and UDP)

NTP (UDP)

DHCP (UDP)

DNS (TCP and UDP)

ChangePassword


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LDAP protocol

Binary protocol Defined using ASN.1

BER encoded

TCP bas e d

Connected

More than one message type


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Decoding

Problem : it's a 2 level protocol TLVs

Ldap

TLV means Type/Length/Value Each of those three elements can be

longer than one byte

A Value can contains other TLVs


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LDAP messages

10 different requests Bind, Unbind, Abandon, Add, Compare,

Delete, Modify, ModifyDN, Search,

Extended 11 different responses

Bind, SearchResEntry, SearchResDone,

S e a rchRe s Re f, Add, Compare , De le te ,Modify, ModifyDN, Extended,

Intermediate


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Server Side

The chain will contain the SSL filter,plus an executor, and the Ldap

protocol codec

We may have expensive requests We want more than one handler

Ea ch s e s s ion conta ins us e r's da ta s


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Handlersc l a s s L d a p P r o t o c o l Ha n d l e r e x t e n d s De mu x i n g I o Ha n d l e r

{

. . .

p u b l i c v o i d me s s a g e Re c e i v e d ( I o S e s s i o n s e s s i o n , Ob j e c t me s s a g e )

{

. . . / / S S L a n d c o n t r o l s Ha n d l i n g

s u p e r . me s s a g e Re c e i v e d ( s e s s i o n , me s s a g e ) ;

}

. . .}

p u b l i c v o i d me s s a g e Re c e i v e d ( I o S e s s i o n s e s s i o n , Ob j e c t me s s a g e )

{

Me s s a g e Ha n d l e r < Ob j e c t > h a n d l e r =

f i n d Re c e i v e d Me s s a g e Ha n d l e r ( me s s a g e . g e t Cl a s s ( ) ) ;

i f ( h a n d l e r ! = n u l l ) {

h a n d l e r . h a n d l e Me s s a g e ( s e s s i o n , me s s a g e ) ;

} e l s e {

t h r o w n e w Un k n o wn Me s s a g e Ty p e Ex c e p t i o n ( . . . ) ; ;

}

}


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Back to basic...


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What about XML ?

Tagged language Size is unknown

Parser are a bit a pain to use at this

point

Seems like XML is the Lingua Franca

those days... a language used by people of diverse speech to communicate with one another,

often a basic form of speech with simplified grammar.


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An XML stripper server

We want to extract the message in anXML message, and return it to the user

The message can be big

The decoder is the main concern...

We have to validate the data before

sending it to the handler.


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XML serverpublic static void main( String[] args ) throws Exception {

IoHandler xmlStripperProtocolHandler = new XmlStripperProtocolHandler();

SocketAcceptor acceptor = new NioSocketAcceptor();

acceptor.setReuseAddress( true );

a cce ptor.s e tHa ndle r( xmlS trippe rProtocolHandler );

// Add the codec filter

a cce ptor.ge tFilterCha in().add La s t( "code c",

new ProtocolCodecFilter( new XmlStripperProtocolCodecFactory() ) );

// S ta rt the lis te ne r

acceptor.bind(new InetSocketAddress(IP_PORT_DEFAULT));

}


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XML handler

public void messageReceived( IoSession session, Object message )

{

Document document = (Document)message;

// S trip the XML from the

String result = getChildren( document.getFirstChild() );

session.write( result );

}


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XML codec factorypublic c la s s XmlS trippe rProtocolCode cFa ctory imple me nts ProtocolCode cFa ctory

{

rS30B pw q#u o+3C33 $pw q#u @qrStrS @w vSory


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XML decoderprotected boolean doDecode( IoSession session, IoBuffer ioBuffer,

ProtocolDecoderOutput decoderOutput ) {

...

dec ode rOutput.write( pa rse rXML( da ta ) );

...

}

public Object parserXML( IoBuffer xmlBuffer ) {

byte[] data = new byte[xmlBuffer.limit()];

xmlBuffer.get( data );

String xml = new String(data).trim();

Document document = DocumentBuilderFactory.newInstance().

newDocumentBuilder().parse(

new ByteArrayInputStream( xml.getBytes() ) );

return (document);

}


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Do's and Don'ts


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Do's !!!

Follow the KISS principle Keep the chain short

Do not use an executor if not needed

Tune the number of IoProcessors

Use only one codec filter

If you have a problem, then yourcode c/ha ndle r proba bly s ucks ...


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DON'Ts !!!

Don't use the logging filter. Use Log4j. Your filter must be thread-safe

Don't expect that you will receive data

in one single block

Don't forget about the negative impact

Nagle's algorithm has on performance

Don't use Direct buffers unless

a bs olute ly ne e de d...


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Mina in Real Life ASEU-2009