Blocking IO

stream_socket_accept($server, -1)

Why is this a problem?

Blocking IO

Common Latencies

https://gist.github.com/jboner/2841832

Common Latencies

https://gist.github.com/jboner/2841832

C10k Problem

You can buy a 1000MHz machine with 2 gigabytes of RAM and an 1000Mbit/sec Ethernet card for $1200 or so. At 20000 clients, that’s 50KHz, 100Kbytes, and 50Kbits/sec per client.

It shouldn’t take any more horsepower than that to take four kilobytes from the disk and send them to the network once a second for each of twenty thousand clients.

So hardware is no longer the bottleneck.

http://www.kegel.com/c10k.html

Threading

Non-blocking IO

Reactor Pattern

React’s Stack

Event Loop

• Tracks timers and streams
• Each loop iteration is a "tick"
• Ticks execute timers and poll IO
• Polling timeout can be calculated
• No timers/streams ends loop

Event Loop

Streams

Readable → Writable

CompositeStream

Joins writable and readable streams

ThroughStream

Allows data to be filtered

BufferedSink

Converts writable stream to a promise

Promises

Wouldn’t it be nice if asynchronous
functions could return immediately?

Deferred

• promise()
• resolve($value = null)
• reject($reason = null)
• progress($update = null)

Computation or unit of work that
may not have completed yet

Promise

Placeholder for the result of a deferred computation

then($onFulfilled, $onRejected, $onProgress)

then() returns a new Promise composing the first

Suggested Reading

“You’re missing the point of promises”
— Domenic Denicola

Now back to the stack…

Avoid Blocking

• Database queries
• Disk and file IO
• CPU-intensive tasks

Helpful Tools

Inter-process communication

Message queues

Break up computations with
$loop->nextTick(callable)