ComponentsThreadChannel::isFull()

ThreadChannel::isFull ​

(PHP 8.6+, True Async 1.0)

php
public ThreadChannel::isFull(): bool

Returns true if the channel buffer has reached its maximum capacity.

For an unbuffered channel (capacity = 0), this always returns true because there is no buffer — every send() must wait for a matching recv().

isFull() is thread-safe. The result reflects the state at the moment of the call; another thread may drain a slot immediately afterward.

Return values ​

true — the buffer is at capacity (or it is an unbuffered channel). false — the buffer has at least one free slot.

Examples ​

Example #1 Checking buffer fullness before sending ​

php
<?php

use Async\ThreadChannel;

$channel = new ThreadChannel(3);

echo $channel->isFull() ? "full" : "has space"; // "has space"

$channel->send('x');
$channel->send('y');
$channel->send('z');

echo $channel->isFull() ? "full" : "has space"; // "full"

Example #2 Back-pressure monitoring in a producer thread ​

php
<?php

use Async\ThreadChannel;
use function Async\spawn;
use function Async\spawn_thread;
use function Async\await;

spawn(function() {
    $channel = new ThreadChannel(10);

    $producer = spawn_thread(function() use ($channel) {
        $items = range(1, 30);
        foreach ($items as $item) {
            if ($channel->isFull()) {
                // Buffer is currently full — send() will block;
                // log back-pressure for observability
                error_log("ThreadChannel back-pressure: buffer full");
            }
            $channel->send($item); // blocks until space is available
        }
        $channel->close();
    });

    $consumer = spawn_thread(function() use ($channel) {
        try {
            while (true) {
                // Simulate slow consumer
                $val = $channel->recv();
                // process $val ...
            }
        } catch (\Async\ThreadChannelException) {
            echo "Done\n";
        }
    });

    await($producer);
    await($consumer);
});

See also ​