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Add lock function #34

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12 changes: 11 additions & 1 deletion composer.json
Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,8 @@
"require": {
"amphp/amp": "^2",
"amphp/byte-stream": "^1",
"amphp/parallel": "^1"
"amphp/parallel": "^1",
"amphp/sync": "^1.0"
},
"require-dev": {
"amphp/phpunit-util": "^1",
Expand All @@ -56,5 +57,14 @@
"platform": {
"php": "7.0.0"
}
},
"scripts": {
"check": [
"@cs",
"@test"
],
"cs": "PHP_CS_FIXER_IGNORE_ENV=1 php-cs-fixer fix -v --diff --dry-run",
"cs-fix": "PHP_CS_FIXER_IGNORE_ENV=1 php-cs-fixer fix -v --diff",
"test": "@php -dzend.assertions=1 -dassert.exception=1 ./vendor/bin/phpunit --coverage-text"
}
}
80 changes: 80 additions & 0 deletions lib/functions.php
Original file line number Diff line number Diff line change
Expand Up @@ -2,8 +2,14 @@

namespace Amp\File;

use Amp\CancellationToken;
use Amp\Delayed;
use Amp\Loop;
use Amp\NullCancellationToken;
use Amp\Promise;
use Amp\Sync\Lock;

use function Amp\call;

const LOOP_STATE_IDENTIFIER = Driver::class;

Expand Down Expand Up @@ -350,3 +356,77 @@ function put(string $path, string $contents): Promise
{
return filesystem()->put($path, $contents);
}

/**
* Asynchronously lock a file
* Resolves with a callable that MUST eventually be called in order to release the lock.
*
* @param string $file File to lock
* @param bool $shared Whether to acquire a shared or exclusive lock (\LOCK_SH or \LOCK_EX, see PHP flock docs)
* @param integer $polling Polling interval for lock in milliseconds
* @param CancellationToken $token Cancellation token
*
* @return \Amp\Promise Resolves with an \Amp\Sync\Lock
*/
function lock(string $file, bool $shared, int $polling = 100, CancellationToken $token = null): Promise
{
return call(static function () use ($file, $shared, $polling, $token) {
$operation = $shared ? \LOCK_SH : \LOCK_EX;
$token = $token ?? new NullCancellationToken;
if (!yield exists($file)) {
yield \touch($file);
StatCache::clear($file);
}
$operation |= LOCK_NB;
$res = \fopen($file, 'c');
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Shouldn't we just open the file here instead of the additional touch above?

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Well technically yes, but then the touching wouldn't be async.

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Well, the fopen isn't async anyway? I guess we'd have to add the function to Handle to have it really async?

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Well, fopen isn't async, but afaik there is no way to obtain a lock using any of the native async libs supported by amphp.
I thought it'd be nice if we could make at least the touch part of the fopen async.

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@trowski What's your opinion here?

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I'm rather uncomfortable introducing anything that can block when it could be rolled into a simple Task executed using parallel.


while (!\flock($res, $operation, $wouldblock)) {
if (!$wouldblock) {
throw new FilesystemException("Failed acquiring lock on file.");
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Should we check for the file being deleted here and recreate it? I guess it could make sense to delete after unlocking, but not in every case (i.e. only if it's a separate lock file).

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I really don't think this is the place for such logic

}
yield new Delayed($polling);
$token->throwIfRequested();
}

return new Lock(
0,
static function () use (&$res) {
if ($res) {
\flock($res, LOCK_UN);
\fclose($res);
$res = null;
}
}
);
});
}

/**
* Asynchronously lock a file (shared lock)
* Resolves with a callable that MUST eventually be called in order to release the lock.
*
* @param string $file File to lock
* @param integer $polling Polling interval for lock in milliseconds
* @param CancellationToken $token Cancellation token
*
* @return \Amp\Promise Resolves with a callable that MUST eventually be called in order to release the lock.
*/
function lockShared(string $file, int $polling = 100, CancellationToken $token = null): Promise
{
return lock($file, true, $polling, $token ?? new NullCancellationToken);
}

/**
* Asynchronously lock a file (exclusive lock)
* Resolves with a callable that MUST eventually be called in order to release the lock.
*
* @param string $file File to lock
* @param integer $polling Polling interval for lock in milliseconds
* @param CancellationToken $token Cancellation token
*
* @return \Amp\Promise Resolves with a callable that MUST eventually be called in order to release the lock.
*/
function lockExclusive(string $file, int $polling = 100, CancellationToken $token = null): Promise
{
return lock($file, false, $polling, $token ?? new NullCancellationToken);
}
89 changes: 88 additions & 1 deletion test/HandleTest.php
Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,13 @@
namespace Amp\File\Test;

use Amp\ByteStream\ClosedException;
use Amp\Delayed;
use Amp\File;
use Amp\PHPUnit\TestCase;
use Amp\Sync\Lock;
use Amp\TimeoutCancellationToken;

use function Amp\Promise\timeout;

abstract class HandleTest extends TestCase
{
Expand Down Expand Up @@ -232,7 +237,89 @@ public function testMode()
yield $handle->close();
});
}

/**
* Try locking file exclusively.
*
* @param string $file File
* @param int $polling Polling interval
* @param int $timeout Lock timeout
* @return void
*/
private function tryLockExclusive(string $file, int $polling, int $timeout)
{
return File\lockExclusive($file, $polling, new TimeoutCancellationToken($timeout));
}
/**
* Try locking file in shared mode.
*
* @param string $file File
* @param int $polling Polling interval
* @param int $timeout Lock timeout
* @return void
*/
private function tryLockShared(string $file, int $polling, int $timeout)
{
return File\lockShared($file, $polling, new TimeoutCancellationToken($timeout));
}
public function testExclusiveLock()
{
$this->execute(function () {
$primary = null;
$secondary = null;
try {
try {
$primary = yield $this->tryLockExclusive(__FILE__, 100, 100);
$this->assertInstanceOf(Lock::class, $primary);

$unlocked = false;
$try = $this->tryLockShared(__FILE__, 100, 10000);
$try->onResolve(static function ($e, $secondaryUnlock) use (&$unlocked, &$secondary) {
if ($e) {
throw $e;
}
$unlocked = true;
$secondary = $secondaryUnlock;
});

$this->assertFalse($unlocked, "The lock wasn't acquired");
} finally {
if ($primary) {
$primary->release();
}
}

yield new Delayed(100 * 2);
$this->assertTrue($unlocked, "The lock wasn't released");

yield $try;
$this->assertInstanceOf(Lock::class, $secondary);
} finally {
if ($secondary) {
$secondary->release();
}
}
});
}
public function testSharedLock()
{
$this->execute(function () {
$primary = null;
$secondary = null;
try {
$primary = yield $this->tryLockShared(__FILE__, 100, 100);
$this->assertInstanceOf(Lock::class, $primary);
$secondary = yield $this->tryLockShared(__FILE__, 100, 100);
$this->assertInstanceOf(Lock::class, $secondary);
} finally {
if ($primary) {
$primary->release();
}
if ($secondary) {
$secondary->release();
}
}
});
}
public function testClose()
{
$this->execute(function () {
Expand Down