PHP Swoole Writing large dataset as json into file

functions.php

<?php

// functions.php
function memoryStats($real = false) {
  return memory_get_usage($real);
}

function memoryStatsHuman($real = false) {
  return (memoryStats($real) / 1024) . ' MB';
}

php-json-large-data.php

<?php

require_once './functions.php';
require_once './vendor/autoload.php';

$allocatedMemory = memoryStatsHuman(true);
echo 'Allocated memory:  ', $allocatedMemory, PHP_EOL;

$startTime = microtime(true);

echo 'Before loop memory usage: ', memoryStatsHuman(false), PHP_EOL;

$filename = __DIR__ . '/json-files/records-250000.json';

// use the factory to create a Faker\Generator instance
function generatorData() {
  $faker = Faker\Factory::create();
  $numRows = 250000;

  for ($i = 0; $i < $numRows; $i++) {
    yield [
      'name' => $faker->name,
      'email' => $faker->email,
      'spent' => $faker->randomFloat(15),
      'start_date' => $faker->date(),
      'end_date' => $faker->date(),
      'cpa' => $faker->randomNumber(7),
      'cpm' => $faker->randomFloat(10),
      'created_at' => date('Y-m-d H:i:s'),
    ];
    // echo $i,PHP_EOL;
  }
}

// Swoole\Runtime::enableCoroutine();
// $data = new SplFixedArray($numRows);
// $rawData = [
//   'records' => $data, // This fails memory exhausted when working with normal array
//   'recordCount' => $data>getSize(),
// ];

$fp = null;
$fp = fopen($filename, 'ab+');

// You need to know how you need to create JSON file and create accordingly
go(function() use ($fp) {

  Swoole\Coroutine\System::fwrite($fp, '{' . PHP_EOL . '"records":[' . PHP_EOL);

  foreach (generatorData() as $key => $data) {
    // print_r($data);
    $json = $jsonStr = '';
    $json = json_encode($data);
    $jsonStr = (0 !== $key) ? ',' . PHP_EOL . $json : $json;
    $bytesWrote = Swoole\Coroutine\System::fwrite($fp,  $jsonStr);
    // echo "bytes wrote {$bytesWrote} \n";
  }

  // metadata
  $metadata = [
    'recordCount' => $key + 1 // array starts with 0, so +1 added
  ];

  $metaStr = '],' . PHP_EOL . '"metadata":' . json_encode($metadata);
  Swoole\Coroutine\System::fwrite($fp,  $metaStr);

  Swoole\Coroutine\System::fwrite($fp, PHP_EOL . '}' . PHP_EOL);
  fclose($fp);

  $memoryUsed = memoryStatsHuman(false);
  $endTime = microtime(true);
  $timeTaken = $endTime - $startTime;

  echo 'Actual memory usage: ', $memoryUsed, PHP_EOL;
  echo 'Total time taken: ', $timeTaken, ' seconds', PHP_EOL;

});

/**

Allocated memory:  2048 MB
Before loop memory usage: 1261.5859375 MB
Actual memory usage: 2946.8125 MB
Total time taken: 1587224980.5645 seconds
*/