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Use round robin for happy eyeballs DNS responses (load balancing)
The happy eyeballs algorithms tries to connect over both IPv6 and IPv4 at the same time. Accordingly, the hostname has to be resolved for both address families which both may potentially contain any number of records (load balancing). This changeset randomizes the order of returned IP addresses per address family. This means that if multiple records are returned, it will try to connect to a random one from this list instead of always trying the first. This allows the load to be distributed more evenly across all returned IP addresses. This can be used as a very basic DNS load balancing mechanism.
1 parent e2b96b2 commit 16ff9ad

3 files changed

Lines changed: 59 additions & 50 deletions

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‎src/HappyEyeBallsConnectionBuilder.php‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -316,6 +316,7 @@ public function hasBeenResolved()
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*/
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public function mixIpsIntoConnectQueue(array $ips)
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{
319+
\shuffle($ips);
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$this->ipsCount += \count($ips);
320321
$connectQueueStash = $this->connectQueue;
321322
$this->connectQueue = array();

‎tests/HappyEyeBallsConnectionBuilderTest.php‎

Lines changed: 58 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -302,8 +302,8 @@ public function testConnectWillStartConnectingWithAlternatingIPv6AndIPv4WhenReso
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$connector->expects($this->exactly(4))->method('connect')->withConsecutive(
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array('tcp://[::1]:80?hostname=reactphp.org'),
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array('tcp://127.0.0.1:80?hostname=reactphp.org'),
305-
array('tcp://[::2]:80?hostname=reactphp.org'),
306-
array('tcp://127.0.0.2:80?hostname=reactphp.org')
305+
array('tcp://[::1]:80?hostname=reactphp.org'),
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array('tcp://127.0.0.1:80?hostname=reactphp.org')
307307
)->willReturnOnConsecutiveCalls(
308308
$deferred->promise(),
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$deferred->promise(),
@@ -316,8 +316,8 @@ public function testConnectWillStartConnectingWithAlternatingIPv6AndIPv4WhenReso
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array('reactphp.org', Message::TYPE_AAAA),
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array('reactphp.org', Message::TYPE_A)
318318
)->willReturnOnConsecutiveCalls(
319-
\React\Promise\resolve(array('::1', '::2')),
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\React\Promise\resolve(array('127.0.0.1', '127.0.0.2'))
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\React\Promise\resolve(array('::1', '::1')),
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\React\Promise\resolve(array('127.0.0.1', '127.0.0.1'))
321321
);
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$uri = 'tcp://reactphp.org:80';
@@ -341,7 +341,7 @@ public function testConnectWillStartConnectingWithAttemptTimerWhenOnlyIpv6Resolv
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$connector = $this->getMockBuilder('React\Socket\ConnectorInterface')->getMock();
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$connector->expects($this->exactly(2))->method('connect')->withConsecutive(
343343
array('tcp://[::1]:80?hostname=reactphp.org'),
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array('tcp://[::2]:80?hostname=reactphp.org')
344+
array('tcp://[::1]:80?hostname=reactphp.org')
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)->willReturnOnConsecutiveCalls(
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\React\Promise\reject(new \RuntimeException()),
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new Promise(function () { })
@@ -352,7 +352,7 @@ public function testConnectWillStartConnectingWithAttemptTimerWhenOnlyIpv6Resolv
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array('reactphp.org', Message::TYPE_AAAA),
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array('reactphp.org', Message::TYPE_A)
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)->willReturnOnConsecutiveCalls(
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\React\Promise\resolve(array('::1', '::2')),
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\React\Promise\resolve(array('::1', '::1')),
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\React\Promise\reject(new \RuntimeException())
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);
358358

@@ -799,4 +799,56 @@ public function testCleanUpCancelsAllPendingConnectionAttemptsWithoutStartingNew
799799

800800
$builder->cleanUp();
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}
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public function testMixIpsIntoConnectQueueSometimesAssignsInOriginalOrder()
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{
805+
$loop = $this->getMockBuilder('React\EventLoop\LoopInterface')->getMock();
806+
$connector = $this->getMockBuilder('React\Socket\ConnectorInterface')->getMock();
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$resolver = $this->getMockBuilder('React\Dns\Resolver\ResolverInterface')->getMock();
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809+
$uri = 'tcp://reactphp.org:80/path?test=yes#start';
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$host = 'reactphp.org';
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$parts = parse_url($uri);
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for ($i = 0; $i < 100; ++$i) {
814+
$builder = new HappyEyeBallsConnectionBuilder($loop, $connector, $resolver, $uri, $host, $parts);
815+
$builder->mixIpsIntoConnectQueue(array('::1', '::2'));
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817+
$ref = new \ReflectionProperty($builder, 'connectQueue');
818+
$ref->setAccessible(true);
819+
$value = $ref->getValue($builder);
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821+
if ($value === array('::1', '::2')) {
822+
break;
823+
}
824+
}
825+
826+
$this->assertEquals(array('::1', '::2'), $value);
827+
}
828+
829+
public function testMixIpsIntoConnectQueueSometimesAssignsInReverseOrder()
830+
{
831+
$loop = $this->getMockBuilder('React\EventLoop\LoopInterface')->getMock();
832+
$connector = $this->getMockBuilder('React\Socket\ConnectorInterface')->getMock();
833+
$resolver = $this->getMockBuilder('React\Dns\Resolver\ResolverInterface')->getMock();
834+
835+
$uri = 'tcp://reactphp.org:80/path?test=yes#start';
836+
$host = 'reactphp.org';
837+
$parts = parse_url($uri);
838+
839+
for ($i = 0; $i < 100; ++$i) {
840+
$builder = new HappyEyeBallsConnectionBuilder($loop, $connector, $resolver, $uri, $host, $parts);
841+
$builder->mixIpsIntoConnectQueue(array('::1', '::2'));
842+
843+
$ref = new \ReflectionProperty($builder, 'connectQueue');
844+
$ref->setAccessible(true);
845+
$value = $ref->getValue($builder);
846+
847+
if ($value === array('::2', '::1')) {
848+
break;
849+
}
850+
}
851+
852+
$this->assertEquals(array('::2', '::1'), $value);
853+
}
802854
}

‎tests/HappyEyeBallsConnectorTest.php‎

Lines changed: 0 additions & 44 deletions
Original file line numberDiff line numberDiff line change
@@ -270,50 +270,6 @@ public function testCancelDuringTcpConnectionCancelsTcpConnectionIfGivenIp()
270270
$this->loop->run();
271271
}
272272

273-
/**
274-
* @dataProvider provideIpvAddresses
275-
*/
276-
public function testShouldConnectOverIpv4WhenIpv6LookupFails(array $ipv6, array $ipv4)
277-
{
278-
$this->resolver->expects($this->exactly(2))->method('resolveAll')->withConsecutive(
279-
array($this->equalTo('example.com'), Message::TYPE_AAAA),
280-
array($this->equalTo('example.com'), Message::TYPE_A)
281-
)->willReturnOnConsecutiveCalls(
282-
Promise\reject(new \Exception('failure')),
283-
Promise\resolve($ipv4)
284-
);
285-
$this->tcp->expects($this->exactly(1))->method('connect')->with($this->equalTo('1.2.3.4:80?hostname=example.com'))->willReturn(Promise\resolve($this->connection));
286-
287-
$promise = $this->connector->connect('example.com:80');;
288-
$resolvedConnection = Block\await($promise, $this->loop);
289-
290-
self::assertSame($this->connection, $resolvedConnection);
291-
}
292-
293-
/**
294-
* @dataProvider provideIpvAddresses
295-
*/
296-
public function testShouldConnectOverIpv6WhenIpv4LookupFails(array $ipv6, array $ipv4)
297-
{
298-
if (count($ipv6) === 0) {
299-
$ipv6[] = '1:2:3:4';
300-
}
301-
302-
$this->resolver->expects($this->exactly(2))->method('resolveAll')->withConsecutive(
303-
array($this->equalTo('example.com'), Message::TYPE_AAAA),
304-
array($this->equalTo('example.com'), Message::TYPE_A)
305-
)->willReturnOnConsecutiveCalls(
306-
Promise\resolve($ipv6),
307-
Promise\reject(new \Exception('failure'))
308-
);
309-
$this->tcp->expects($this->exactly(1))->method('connect')->with($this->equalTo('[1:2:3:4]:80?hostname=example.com'))->willReturn(Promise\resolve($this->connection));
310-
311-
$promise = $this->connector->connect('example.com:80');;
312-
$resolvedConnection = Block\await($promise, $this->loop);
313-
314-
self::assertSame($this->connection, $resolvedConnection);
315-
}
316-
317273
/**
318274
* @internal
319275
*/

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