X-Git-Url: https://git.dogcows.com/gitweb?a=blobdiff_plain;f=slides.html;h=51f91018b47b58dc661ea16ec0f31ef6e68920f0;hb=309c1da6df9319b3bcd760fd3073bafeda9faf09;hp=9eae8008ce65f65a0a2751af948d93738c50c4ee;hpb=1e5589cbb1518565f28a66bafd4882eec1d9acd5;p=chaz%2Ftalk-event-driven-programming-in-perl

diff --git a/slides.html b/slides.html
index 9eae800..51f9101 100644
--- a/slides.html
+++ b/slides.html
@@ -54,6 +54,9 @@ my $pizza = prepare_and_bake($order, $ingredentials);
 print($pizza);
 ```
 
+???
+But some programs are long-lived.
+
 ---
 ## Event-driven programs
 
@@ -68,8 +71,11 @@ At it's core, event-driven programming is this simple.
 But there are some complications and things to knows, which is why this talk exists.
 
 ---
+name:  graph-eventloop
 class: center, middle
 
+## Event loop
+
 ![Event loop](img/eventloop.svg)
 
 ???
@@ -364,9 +370,30 @@ class: syscalls
 ### syscalls
 
 - [`pause`](http://man.he.net/man2/pause) - Sleeps until signal
+
+--
 - [`select`](http://man.he.net/man2/select), [`poll`](http://man.he.net/man2/poll), [`epoll`](http://man.he.net/man7/epoll), [`kqueue`](https://www.freebsd.org/cgi/man.cgi?format=ascii&sektion=2&query=kqueue) - Monitor multiple file descriptors
+
+--
 - [`clock_gettime`](http://man.he.net/man2/clock_gettime) - What time is it now?
 
+---
+
+## Reactor pattern
+
+.big[
+- Queues events asynchronously.
+- Demultiplexes and dispatches synchronously.
+]
+
+---
+name:  graph-reactor
+class: center, middle
+
+## Reactor pattern
+
+![Reactor](img/reactor.svg)
+
 ---
 class: ex-basicreactor
 
@@ -386,6 +413,25 @@ while (1) {
 }
 ```
 
+---
+class: ex-basicreactor
+
+## The basic reactor
+
+```perl
+our $timers     = [...];
+our $io_handles = [...];
+
+while (1) {
+    my $next_timer = find_next_timer($timers);
+
+*   poll($io_handles, $next_timer->time_from_now);
+
+    handle_ready_io_handles($io_handles);
+    handle_expired_timers($timers);
+}
+```
+
 ---
 
 ## Reactor examples on CPAN
@@ -399,6 +445,149 @@ while (1) {
 - [`Mojo::Reactor::Poll`](https://metacpan.org/source/Mojo::Reactor::Poll)
 ]
 
+---
+name:  not-all-roses
+class: center, middle
+
+![Thorns](img/thorn.jpg)
+
+## Watch out for the thorns...
+
+???
+There are some special considerations you need to take when writing event-driven code.
+
+---
+class: center, middle
+
+## Exceptions for error handling
+
+---
+class: center, middle
+
+### Problem: No exception handler up the call stack
+
+---
+class: ex-exceptions
+
+## Rule: Don't die/throw in event handlers.
+
+--
+### Error callback pattern
+
+```perl
+do_something_asynchronously(
+    callback => sub { ... },
+    on_error => sub { ... },
+);
+```
+
+---
+class: ex-exceptions
+
+## Rule: Don't die/throw in event handlers.
+
+### Use promises
+
+```perl
+my $promise = do_something_asynchronously();
+
+$promise->on_done(sub { ... });
+$promise->on_fail(sub { ... });
+```
+
+---
+class: center, middle
+
+## `SIGPIPE`
+
+---
+class: sigpipe
+## `SIGPIPE`
+
+- Sent to your program when it writes to a pipe that was closed.
+
+--
+- Default signal handler terminates the program.
+
+---
+class: ex-sigpipe
+
+## Solution: Ignore `SIGPIPE`
+
+```perl
+$SIG{PIPE} = 'IGNORE';
+```
+
+???
+Some event loops do this for you.
+
+--
+.big[
+Look for `EPIPE` from syscalls (like [`write`](http://man.he.net/man2/write)) instead.
+
+(You *are* checking return codes from your system calls... right?)
+]
+
+---
+class: center, middle
+
+## Use [`Future::AsyncAwait`](https://metacpan.org/pod/Future::AsyncAwait).
+
+???
+If you have used JavaScript recently, you may have used its "async/await" feature to clean up your non-blocking code.
+
+---
+class: center, middle
+
+### Yes, Perl can do it, too!
+
+---
+class: ex-asyncawait
+
+## Without async and await
+
+```perl
+use Future;
+
+sub do_two_things {
+    return do_first_thing()->then(sub {
+        my $first = shift;
+
+        return do_second_thing($first)->then(sub {
+            my $second = shift;
+
+            return Future->done([$first, $second]);
+        });
+    });
+}
+```
+
+---
+class: ex-asyncawait
+
+## With async and await
+
+```perl
+use Future::AsyncAwait;
+
+async sub do_two_things
+{
+    my $first = await do_first_thing();
+
+    my $second = await do_second_thing($first);
+
+    return [$first, $second];
+}
+```
+
+???
+There are caveats: Localized variable assignments don't work, nor anything that has implied local-like behavior.
+---
+
+## Events in the world
+
+
+
 ---
 class: center, middle
 name:  conclusion