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<?php
/*
* This file is part of the Fidry CPUCounter Config package.
*
* (c) Théo FIDRY <theo.fidry@gmail.com>
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*/
declare(strict_types=1);
namespace Fidry\CpuCoreCounter;
use Fidry\CpuCoreCounter\Finder\CpuCoreFinder;
use Fidry\CpuCoreCounter\Finder\EnvVariableFinder;
use Fidry\CpuCoreCounter\Finder\FinderRegistry;
use InvalidArgumentException;
use function implode;
use function max;
use function sprintf;
use function sys_getloadavg;
use const PHP_EOL;
final class CpuCoreCounter
{
/**
* @var list<CpuCoreFinder>
*/
private $finders;
/**
* @var positive-int|null
*/
private $count;
/**
* @param list<CpuCoreFinder>|null $finders
*/
public function __construct(?array $finders = null)
{
$this->finders = $finders ?? FinderRegistry::getDefaultLogicalFinders();
}
/**
* @param positive-int|0 $reservedCpus Number of CPUs to reserve. This is useful when you want
* to reserve some CPUs for other processes. If the main
* process is going to be busy still, you may want to set
* this value to 1.
* @param non-zero-int|null $countLimit The maximum number of CPUs to return. If not provided, it
* may look for a limit in the environment variables, e.g.
* KUBERNETES_CPU_LIMIT. If negative, the limit will be
* the total number of cores found minus the absolute value.
* For instance if the system has 10 cores and countLimit=-2,
* then the effective limit considered will be 8.
* @param float|null $loadLimit Element of [0., 1.]. Percentage representing the
* amount of cores that should be used among the available
* resources. For instance, if set to 0.7, it will use 70%
* of the available cores, i.e. if 1 core is reserved, 11
* cores are available and 5 are busy, it will use 70%
* of (11-1-5)=5 cores, so 3 cores. Set this parameter to null
* to skip this check. Beware that 1 does not mean "no limit",
* but 100% of the _available_ resources, i.e. with the
* previous example, it will return 5 cores. How busy is
* the system is determined by the system load average
* (see $systemLoadAverage).
* @param float|null $systemLoadAverage The system load average. If passed, it will use
* this information to limit the available cores based
* on the _available_ resources. For instance, if there
* is 10 cores but 3 are busy, then only 7 cores will
* be considered for further calculation. If set to
* `null`, it will use `sys_getloadavg()` to check the
* load of the system in the past minute. You can
* otherwise pass an arbitrary value. Should be a
* positive float.
*
* @see https://php.net/manual/en/function.sys-getloadavg.php
*/
public function getAvailableForParallelisation(
int $reservedCpus = 0,
?int $countLimit = null,
?float $loadLimit = null,
?float $systemLoadAverage = 0.
): ParallelisationResult {
self::checkCountLimit($countLimit);
self::checkLoadLimit($loadLimit);
self::checkSystemLoadAverage($systemLoadAverage);
$totalCoreCount = $this->getCountWithFallback(1);
$availableCores = max(1, $totalCoreCount - $reservedCpus);
// Adjust available CPUs based on current load
if (null !== $loadLimit) {
$correctedSystemLoadAverage = null === $systemLoadAverage
? sys_getloadavg()[0] ?? 0.
: $systemLoadAverage;
$availableCores = max(
1,
$loadLimit * ($availableCores - $correctedSystemLoadAverage)
);
}
if (null === $countLimit) {
$correctedCountLimit = self::getKubernetesLimit();
} else {
$correctedCountLimit = $countLimit > 0
? $countLimit
: max(1, $totalCoreCount + $countLimit);
}
if (null !== $correctedCountLimit && $availableCores > $correctedCountLimit) {
$availableCores = $correctedCountLimit;
}
return new ParallelisationResult(
$reservedCpus,
$countLimit,
$loadLimit,
$systemLoadAverage,
$correctedCountLimit,
$correctedSystemLoadAverage ?? $systemLoadAverage,
$totalCoreCount,
(int) $availableCores
);
}
/**
* @throws NumberOfCpuCoreNotFound
*
* @return positive-int
*/
public function getCount(): int
{
// Memoize result
if (null === $this->count) {
$this->count = $this->findCount();
}
return $this->count;
}
/**
* @param positive-int $fallback
*
* @return positive-int
*/
public function getCountWithFallback(int $fallback): int
{
try {
return $this->getCount();
} catch (NumberOfCpuCoreNotFound $exception) {
return $fallback;
}
}
/**
* This method is mostly for debugging purposes.
*/
public function trace(): string
{
$output = [];
foreach ($this->finders as $finder) {
$output[] = sprintf(
'Executing the finder "%s":',
$finder->toString()
);
$output[] = $finder->diagnose();
$cores = $finder->find();
if (null !== $cores) {
$output[] = 'Result found: '.$cores;
break;
}
$output[] = '–––';
}
return implode(PHP_EOL, $output);
}
/**
* @throws NumberOfCpuCoreNotFound
*
* @return positive-int
*/
private function findCount(): int
{
foreach ($this->finders as $finder) {
$cores = $finder->find();
if (null !== $cores) {
return $cores;
}
}
throw NumberOfCpuCoreNotFound::create();
}
/**
* @throws NumberOfCpuCoreNotFound
*
* @return array{CpuCoreFinder, positive-int}
*/
public function getFinderAndCores(): array
{
foreach ($this->finders as $finder) {
$cores = $finder->find();
if (null !== $cores) {
return [$finder, $cores];
}
}
throw NumberOfCpuCoreNotFound::create();
}
/**
* @return positive-int|null
*/
public static function getKubernetesLimit(): ?int
{
$finder = new EnvVariableFinder('KUBERNETES_CPU_LIMIT');
return $finder->find();
}
private static function checkCountLimit(?int $countLimit): void
{
if (0 === $countLimit) {
throw new InvalidArgumentException(
'The count limit must be a non zero integer. Got "0".'
);
}
}
private static function checkLoadLimit(?float $loadLimit): void
{
if (null === $loadLimit) {
return;
}
if ($loadLimit < 0. || $loadLimit > 1.) {
throw new InvalidArgumentException(
sprintf(
'The load limit must be in the range [0., 1.], got "%s".',
$loadLimit
)
);
}
}
private static function checkSystemLoadAverage(?float $systemLoadAverage): void
{
if (null !== $systemLoadAverage && $systemLoadAverage < 0.) {
throw new InvalidArgumentException(
sprintf(
'The system load average must be a positive float, got "%s".',
$systemLoadAverage
)
);
}
}
}