Nginx error: 502 Bad Gateway. ZF2, APC and segmentation fault.

I tried Zend Framework 2 for my last project. When everything was done with development I moved project to production server but every time I tried to open project url in bowser Nginx returned an error:

502 bad gateway

Server is running under Debian, also I have installed Nginx(1.2.6) + PHP(5.3.20) and PHP-FPM.

Increasing buffer size and read timeout value in Nginx config had no results, still 502 error. I've looked into Nginx logs and found next entries:

… recv() failed (104: Connection reset by peer) while reading response header from upstream ...

So, it seems that problem is not in Nginx config. Something is wrong with backend. PHP-FPM log contains plenty of entries like next:

php5-fpm.log:
WARNING: [pool www] child 7050 exited on signal 11 (SIGSEGV) after 14.101753 seconds from start

Well, something is causing segmentation fault. I'm hosting a lot of projects on this server and everything was fine, problem appeared only for the last project that was developed using ZF2.

Googling a little bit, I found that some of PHP extensions can cause segmentation fault. One by one I started disabling PHP-extensions. After I disabled APC extension problem disappeared and everything started working fine. So, disabling APC extension helped to solve the problem and seems that ZF2 has some problems with APC, or APC has some problems with ZF2 :)

Will try to make some research what exactly was the reason of this problem and post here if I'll find something interesting.

ZF2: Get db adapter without service locator usage

The problem is: I need to get the instance of TableGateway directly, not via service locator. TableGateway object requires configured dbAdapter object passed to gateway constructor.

Next solution can help with this problem:

1. Use GlobalAdaperFeature as static storage for dbAdapter:

use Zend\Db\TableGateway\Feature;


$feature = new Feature\GlobalAdapterFeature();

2. Add bootstrap method to module config:

public function onBootstrap($e)
{
    // set static adapter for all module table gateways

    $serviceManager = $e->getApplication()->getServiceManager();

    $dbAdapter = $serviceManager->get('Zend\Db\Adapter\Adapter');

    Feature\GlobalAdapterFeature::setStaticAdapter($dbAdapter);
}

3. Now it is possible to get access to already loaded dbAdapter object in TableGateway constructor:

public function __construct()
{
    $this->featureSet = new Feature\FeatureSet();

    $this->featureSet->addFeature(new Feature\GlobalAdapterFeature());

    $this->initialize();
}

So we have dbAdapter injected into gateway constructor. Ofcourse, it's not best practice, but this allows to add some flexibility to your application, and anyway object dbAdapter was instantiated via service locator, but only once for all tableGateways on the stage of module bootstraping.

Zend Framework 2: Disable layout rendering

In ZF1.x we have method for disabling layout rendering that looks like:

$this->_helper->layout()->disableLayout(); 

Of course in ZF2 this method doesn't work but there are some other ways how it is possible to do:

1. Set viewModel as standalone model in controller action:

public function someAction() {
    $viewModel = new ViewModel(array(
        'foo' => 'bar'
    ));

    $viewModel->setTerminal(true);

    return $viewModel;
}

2. Create empty layout and use it in controller action:

Create almost empty layout: module/MyModule/view/layout/empty.phtml with only content:

<?php echo $this->content; ?>

Then use this layout in controller action:

$this->layout('layout/empty');

3. Use response object for output content:

$response = $this->getResponse();
$response->setContent("Some content"); 
return $response;

That's all. May be there are some other ways to do this. As for me I prefer the first way, it looks simple and clean.