MODX having a hard time on Rackspace Cloud Sites

17 Posts

adskiremote Reply #21, 13 years, 9 months ago

Quote from: zerreissen at Dec 12, 2012, 02:28 PM

So, it would appear that even though the newer versions of Modx is giving the ability to disable flock, it appears that the application is still using flock. I still see errors "Exclusive locks are not supported for this stream" on a site that has had flock disabled using the new variables in the latest version (./core/xpdo/xpdo.class.php: const OPT_USE_FLOCK = 'false';
)

On a host such as GoDaddy, you probably won't see the file corruption because of their single node environment (we use a multi node environment).

Speaking of multi node, Modx looks to be using the process PID, which won't work reliably on our environment as the same PIDs can be re-used at the same time in our environment on the different nodes. A more reliable process might be to use the hostname/servername in conjuction with the PID.

OpenGeek - can you offer any insight into trying this?

Thank you

101 Posts

Shawn Himelberger Reply #22, 13 years, 9 months ago

HUZZAH! Finally some real actionable information. Thanks zerrelssen, it's goot to know you're on the inside helping on this.

Shawn Himmelberger
Himmelberger Design
https://himmdesign.com/services/website-development/modx"" target="_blank" rel="nofollow"> MODx Web Design | https://himmdesign.com/services/website-development/modx"" target="_blank" rel="nofollow"> MODx Web Development

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77 Posts

Dylan Wood Reply #23, 13 years, 9 months ago

So this looks like something that modx will need to address!

MODX Staff
10,725 Posts

opengeek Reply #24, 13 years, 9 months ago

Quote from: zerreissen at Dec 12, 2012, 02:28 PM

So, it would appear that even though the newer versions of Modx is giving the ability to disable flock, it appears that the application is still using flock. I still see errors "Exclusive locks are not supported for this stream" on a site that has had flock disabled using the new variables in the latest version (./core/xpdo/xpdo.class.php: const OPT_USE_FLOCK = 'false';
)

First, you do not change the constant to a string value of false in the xPDO class to disable flock. You must add this to the config_options array as:

$config_options = array(
    xPDO::OPT_USE_FLOCK => false,
);

When you do this, xPDO uses an alternative method of writing the file that does not rely on flock being reliable. However, my understanding was that the use of LOCK_EX that is triggering this error (when this is configured properly) would fail quietly when used on file_write_contents(). This can easily be worked around by adjusting the call to remove the LOCK_EX option on that call to file_write_contents(). This was already discovered, but I'm not sure it is resolving the problem completely.

Quote from: zerreissen at Dec 12, 2012, 02:28 PM

On a host such as GoDaddy, you probably won't see the file corruption because of their single node environment (we use a multi node environment).

Speaking of multi node, Modx looks to be using the process PID, which won't work reliably on our environment as the same PIDs can be re-used at the same time in our environment on the different nodes. A more reliable process might be to use the hostname/servername in conjuction with the PID.

That is helpful and again, an easy improvement that can be made to the alternative file locking code.

Jason Coward
Chief Architect @ MODX
http://www.jasoncoward.com | http://twitter.com/drumshaman | https://github.com/opengeek

MODX Staff
10,725 Posts

opengeek Reply #25, 13 years, 9 months ago

Maybe this could help. Below is the test script I used to write and compare the alternative file-locking code. Just put this in a php script in your MODX_BASE_PATH and call it using the Apache ab tool, or http_load (my preferred tool), to see how it performs with the various options available for file locking in MODX. Calling it with a higher concurrency level will reveal more lock conflicts.

<?php
include dirname(__FILE__) . '/config.core.php';
include MODX_CORE_PATH . 'model/modx/modx.class.php';

$config = array(
    'log_level' => modX::LOG_LEVEL_INFO,
    'log_target' => XPDO_CLI_MODE ? 'ECHO' : 'HTML',
    xPDO::OPT_USE_FLOCK => false,
    xPDO::OPT_CACHE_ATTEMPTS => 1,
    xPDO::OPT_CACHE_ATTEMPT_DELAY => 250
);

$modx = modX::getInstance('test', $config);
$modx->setLogTarget(XPDO_CLI_MODE ? 'ECHO' : 'HTML');
$modx->setLogLevel(modX::LOG_LEVEL_INFO);

$modx->getCacheManager();

$content = uniqid('contents-');

$result = $modx->cacheManager->writeFile('test-lock.txt', $content);
echo $result ? '1' : '0';

Jason Coward
Chief Architect @ MODX
http://www.jasoncoward.com | http://twitter.com/drumshaman | https://github.com/opengeek

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77 Posts

Dylan Wood Reply #26, 13 years, 9 months ago

I don't think we can call those apache tools in the rackspace environment.... unless you're talking to Chris from Rackspace?

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77 Posts

Dylan Wood Reply #27, 13 years, 9 months ago

I modified this line in the xpdo.class.php

//const OPT_USE_FLOCK = 'use_flock';
const OPT_USE_FLOCK = 'false';

But I am still seeing the issues.

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77 Posts

Dylan Wood Reply #28, 13 years, 9 months ago

Jason - what file should I add this too?

$config_options = array(
xPDO::OPT_USE_FLOCK => false,
);

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77 Posts

Dylan Wood Reply #29, 13 years, 9 months ago

sorry - ok I changed the constant added the config_option and am still seeing the issue. I waited a few minutes in case it was a propagation thing on Rackspace too. Cleared my session to release the class etc etc.

MODX Staff
10,725 Posts

opengeek Reply #30, 13 years, 9 months ago

I've added a new 2.2.7-dev build with a patch to remove the LOCK_EX flag in the xPDOCacheManager::lockFile() method, as well as an attempt at multi-node support using $_SERVER['SERVER_ADDR'] if available, falling back to PHP's gethostname(). Anyone want to give it a whirl on an RS Cloud Sites account? Here they are:

http://modx.s3.amazonaws.com/releases/2.2.7/modx-2.2.7-dev-20121213.zip
http://modx.s3.amazonaws.com/releases/2.2.7/modx-2.2.7-dev-20121213-advanced.zip

Jason Coward
Chief Architect @ MODX
http://www.jasoncoward.com | http://twitter.com/drumshaman | https://github.com/opengeek