80 lines
2.3 KiB
PHP
80 lines
2.3 KiB
PHP
<?php
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namespace App\SSE;
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/**
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* Small class to abstract Server-Sent Events (SSE)
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*
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* https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events
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*/
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class EventLoop
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{
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public int $interval = 3;
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public int $heartbeat = 5; // send heartbeat every num seconds to ensure connection is still alive
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public int $time_limit = 3600;
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public int $exec_limit = 30;
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public function start(callable $callback): void
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{
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// as session data is locked to prevent concurrent writes we
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// make it read only to prevent the server from locking up
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if (session_status() === PHP_SESSION_ACTIVE)
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{
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session_write_close();
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}
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header('Content-Type: text/event-stream');
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// explicitly disable caching so varnish and other upstreams won't cache.
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header('Cache-Control: no-cache, must-revalidate');
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// instruct nginx to disable fastcgi_buffering and disable gzip
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header('X-Accel-Buffering: no');
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// send headers to client indicating we are now a stream
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ob_end_flush();
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flush();
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$expiration_time = time() + $this->time_limit;
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$last_heartbeat = time();
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while (!connection_aborted() && time() < $expiration_time)
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{
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set_time_limit($this->exec_limit);
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try {
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$data = call_user_func($callback);
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if ($data !== NULL)
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{
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$this->send($data);
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$last_heartbeat = time();
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}
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} catch (StopEventLoopException $th) {
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break;
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}
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// sleep and perform heartbeat to ensure connection is still alive
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for ($i = 0; $i < $this->interval; $i++)
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{
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if (time() >= $last_heartbeat + $this->heartbeat)
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{
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echo ": \n\n";
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ob_end_flush();
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flush();
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$last_heartbeat = time();
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}
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sleep(1);
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}
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}
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}
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/**
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* Send data to client encoded as JSON
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*/
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private function send(mixed $data): void
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{
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echo "data: " . json_encode($data);
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echo "\n\n";
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// send data to stream
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ob_end_flush();
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flush();
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}
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} |