Add Loop::now() #208

trowski · 2018-03-20T15:31:52Z

We frequently use microtime() or time() to keep track of last activity time, update time, etc. These system calls are relatively expensive. Loop::now() updates only on the first call in a tick (or in UvLoop the function uv_now() is used).

kelunik · 2018-03-20T15:39:01Z

lib/Loop/UvDriver.php

+     * {@inheritdoc}
+     */
+    public function now(): int {
+        return \uv_now($this->handle);


uv_now is a monotonic timer and not related to the current real time.

Right,that was my intention that will need to be clear through documentation, that Loop::now() is not necessarily wall time, but the loop time in milliseconds.

kelunik · 2018-03-20T15:40:34Z

The event loop should use a monotonic timer for now instead of microtime(). In PHP 7.3 this will be possible without extensions using hrtime(). This doesn't avoid any microtime() calls then.

staabm · 2018-03-20T15:42:22Z

lib/Loop/EvDriver.php

+    private $now;
+
+    /** @var bool */
+    private $nowUpdateNeeded = true;


in the other loop-impls., this defaults to false

Oops, it should be the same to be consistent, though the initial value doesn't matter in this loop.

trowski · 2018-03-20T15:45:47Z

@kelunik Yes, I should have stated that Loop::now() is not meant to be wall time, but only a relative loop time. As implemented here it's usually wall time, but we can improve it in 7.3 with hrtime().

kelunik · 2018-03-25T15:29:35Z

lib/Loop/Driver.php

+     *
+     * @return int
+     */
+    abstract public function now(): int;


This is a BC break.

Ugh… I suppose so. We could add an ExtendedDriver, but I'd rather wait for v3 then.

What about adding the methods in the implementation classes but not in the interface?

@staabm Then it can't be used, because the interface / abstract class doesn't cover it.

Users which dont need to abstract the impl and use it at app level could use it.

Inside amp you couldn‘t

The function is mostly useful in libraries, not in applications, so...

kelunik

This patch breaks BC in the current form and can't be merged into the current version.

bwoebi · 2018-03-27T09:57:37Z

Not sure why this needs to be abstract. Can't we just simply use the NativeLoop::now() implementation within Driver and override it within the individual drivers?

NativeLoop::now() should be a good enough fallback for any case, we just have additional guarantees about monotonicity within other Drivers.

v3 then can make it abstract. But for now simply not requiring abstract should be just fine.

kelunik · 2018-11-25T21:25:11Z

lib/Loop/EvDriver.php

    public function __construct()
    {
        $this->handle = new \EvLoop;
+        $this->nowOffset = (int) (\microtime(true) * self::MILLISEC_PER_SEC);


I'd even randomize it, so e.g. * random_int(1, 100) / 100

kelunik · 2018-11-26T18:41:05Z

lib/Loop/EvDriver.php

    public function __construct()
    {
        $this->handle = new \EvLoop;
+        $this->nowOffset = (int) (\microtime(true) * self::MILLISEC_PER_SEC);
+        $this->now = \random_int(0, $this->nowOffset);


Any reason why $this->now is updated here?

Picking a random starting value for $this->now. It was always 0, but this makes the value returned by Loop::now() unpredictable.

kelunik reviewed Mar 20, 2018

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staabm reviewed Mar 20, 2018

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kelunik reviewed Mar 25, 2018

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kelunik requested changes Mar 25, 2018

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trowski added the v3.x label Mar 25, 2018

trowski force-pushed the loop-now branch 3 times, most recently from c0dd52f to d9a937a Compare November 25, 2018 17:21

Add Loop::now()

dc2601d

trowski force-pushed the loop-now branch from d9a937a to dc2601d Compare November 25, 2018 17:24

Add docs for Loop::now()

ef482bf

kelunik removed the v3.x label Nov 25, 2018

kelunik reviewed Nov 25, 2018

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kelunik mentioned this pull request Nov 26, 2018

Alternative approach to adding Loop::now() #215

Closed

Randomize loop now offset

a8204fa

kelunik reviewed Nov 26, 2018

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kelunik merged commit 5889f4e into master Nov 26, 2018

kelunik deleted the loop-now branch November 26, 2018 20:59

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Add Loop::now() #208

Add Loop::now() #208

trowski commented Mar 20, 2018

kelunik Mar 20, 2018

trowski Mar 20, 2018

kelunik commented Mar 20, 2018

staabm Mar 20, 2018 •

edited

trowski Mar 20, 2018

trowski commented Mar 20, 2018

kelunik Mar 25, 2018

trowski Mar 25, 2018

staabm Mar 25, 2018 •

edited

kelunik Mar 25, 2018 •

edited

staabm Mar 25, 2018

kelunik Mar 25, 2018

kelunik left a comment

bwoebi commented Mar 27, 2018 •

edited

kelunik Nov 25, 2018

trowski Nov 26, 2018

kelunik Nov 26, 2018

trowski Nov 26, 2018

Add Loop::now() #208

Add Loop::now() #208

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trowski commented Mar 20, 2018

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kelunik commented Mar 20, 2018

staabm Mar 20, 2018 • edited

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trowski commented Mar 20, 2018

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staabm Mar 25, 2018 • edited

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staabm Mar 20, 2018 •

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staabm Mar 25, 2018 •

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kelunik Mar 25, 2018 •

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bwoebi commented Mar 27, 2018 •

edited