How Danga::Socket handles asynchronous processing and how to write ...

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YAPC::Asia 2009 Tokyo 2009/9/10 Gosuke Miyashita

Speaker <ul><li>Gosuke Miyashita （ mizzy ） </li></ul><ul><li>Technical manager at paperboy&co. </li></ul><ul><li>Have most...

Agenda <ul><li>Asynchronous processing with event driven programming </li></ul><ul><li>Asynchronous processing with Danga:...

Event driven programming <ul><li>A programming paradigm in which the flow of the program is determined by events </li></ul...

Events <ul><li>I/O </li></ul><ul><ul><li>On I/O read ready or write ready </li></ul></ul><ul><li>Timers </li></ul><ul><ul>...

Main loop <ul><li>Also called “event loop” </li></ul><ul><li>On each loop, check that events are occurred or not, and proc...

Eaxmple of main loop Process timers Wait I/O events Process I/O events Post main loop process

Events supported by Danga::Socket <ul><li>I/O </li></ul><ul><li>Timers </li></ul>

Process I/O events <ul><li>Danga::Socket supports 3 I/O event notification facility </li></ul><ul><ul><li>kqueue </li></ul...

Add I/O watcher with Danga::Socket <ul><li>use base ‘Danga::Socket’; </li></ul><ul><li>sub new { </li></ul><ul><li>#...

Add I/O wathcer (pattern 2) <ul><li>Danga::Socket->AddOtherFds( </li></ul><ul><li>$fd => sub { </li></ul><ul><li># proc...

Add I/O watcher (pattern 3) <ul><li>Danga::Socket::Callback->new( </li></ul><ul><li>handle => $fd , </li></ul><ul><li>o...

Add timer watcher with Danga::Socket <ul><li>Danga::Socket->AddTimer( </li></ul><ul><li>10, </li></ul><ul><li>sub { </li>...

Start main loop with Danga::Socket <ul><li>Danga::Socket->EventLoop(); </li></ul>

Main loop(again) Process Timers Wait I/O events Process I/O events Post main loop process

Perlbal mechanism(as reverse proxy) BackendHTTP ClientProxy TCPListener Client Server ClientProxy Client BackendHTTP Danga...

Perlbal with a plugin (on start_proxy_request hook) BackendHTTP ClientProxy TCPListener Client Server Plugin::Hoge Target ...

Hooks <ul><li>Perlbal has many plugin hooks </li></ul><ul><li>Explain with start_proxy_request hook in this session </li><...

In case of a synchronous plugin ClientProxy TCPListener Client Server Plugin::Sync Client

In case of an asynchronous plugin ClientProxy TCPListener Client Server Plugin::Async Client ClientProxy

How to write asynchronous plugins? <ul><li>Write the main process based on Danga::Socket </li></ul><ul><ul><li>process wit...

How to write asynchronous plugins? <ul><li>When finish asynchronous process, go to next phase </li></ul><ul><ul><li>Call b...

Main process of a plugin <ul><li>package My::Drizzle ; </li></ul><ul><li>use base ‘Danga::Socket’ ; </li></ul><ul><l...

Attention <ul><li>You can also use Danga::Socket::Callback </li></ul><ul><li>You cannot use AddOtherFds() </li></ul><ul><u...

plugin register <ul><li>package Perlbal::Plugin::AsyncDb ; </li></ul><ul><li>sub register { </li></ul><ul><li>my ( $...

$Call asynchronous process <ul><li>sub request_db { </li></ul><ul><li>my Perlbal::ClientProxy $client = shift ; </li><...$

In case of “return 0” BackendHTTP ClientProxy TCPListener Client Server Plugin::Async Go to next step even if Plugin::Asyn...

“ return 1” & “call back” BackendHTTP ClientProxy TCPListener Client Plugin::Async Stop the process and go to main loop Se...

Call back function <ul><li>If plugin process finished, ClientProxy must go to the next process(call BackendHTTP) </li></ul...

Call back function <ul><li>my Perlbal::ClientProxy </li></ul><ul><li>$client = shift ; </li></ul><ul><li>My::Drizzle->n...

Patch of ClientProxy::handle_request <ul><li>- return if $svc->run_hook( </li></ul><ul><li>- 'start_proxy_request', ...

Points of asynchronous Perlbal plugins <ul><li>Process within the Danga::Socket main loop </li></ul><ul><li>return 1 when ...