TDbCache::setValue collisions - TApplicationComponent::getClassFxEvents thrashing cache

[majuca]

HI, since the version 4.2.2, we have a lot error like this:

An idee?

[ctrlaltca]

Possibly related to issue #820 and this change in PR #841: https://github.com/pradosoft/prado/pull/841/files#diff-e89e3dcbd35b5518b965e802e9aa3d2d3ecb051a7c6fe6feaafd0928c17bc277
Is the database mysql/innodb? You should be able to get some more information on the last deadlock with SHOW ENGINE INNODB STATUS;
Also, did you flush (wipe) the cache when upgrading prado version? prado-cli includes a "cache" action to perform the flush

[majuca]

Indeed, I would confirm that problem is related to the issue #820. If I change the application mode to Normal instead of Performance, it seems to be ok. Yes, I'am with mariadb/innodb 10.11.2.

The cache was removed completly.

Maybe the folloing code here in the function TApplicationComponent::getClassFxEvents:

if ($mode === TApplicationMode::Performance || isset(Prado::$classMap[$baseClassName])) {
$_classfx[$className] = $fx;
$cache->set(self::APP_COMPONENT_FX_CACHE, $_classfx);
}

[belisoful]

It is difficult to debug that function. I have three comments:

1. Getting this function right is critical.
2. My apologies.
3. When mode is Performance the cache should always be set because it's not found, so something else is going on

The whole point is to load all the class data once and put it in one place for loading once.

[belisoful]

@majuca The issue is that the code "shouldn't" be getting to that point. The TApplicationSTatePersister should have had the GetClassFxEvents loaded from cache already. That code only runs once to load the cache, and not a second time, unless the cache is manually busted.

If that code is running multiple times (as it seems to be doing in your instance), then the classFxEvents are not being cached properly.

[belisoful]

PS. The TApplicationStatePersister (being loaded) is in the Class map, and would set the cache regardless of being in performance mode. That's the weird part.

[belisoful]

I think I got it. The scope of static $_classfx = null; is not correct. It should be outside the IF statement in the body of the function rather than in the if statement block. put static $_classfx = null; on line 54 rather than line 57.

When $_classfx[$className] = $fx; happens we are working on $_classfx out of scope.

[belisoful]

The bug was there before #820, #820 unlocked the bug, like a Fortnite achievement award. lol.

[majuca]

@belisoful Many thanks for your realy fast fix. I will test it today, I have several server where I can check this.

[belisoful]

Mathematically (technically), this is the issue. and God bless you for having servers to test the correction.

[majuca]

Bad news, I applied the fix on one server and the error still happens, some examples:

#0 /var/www/html/vendor/pradosoft/prado/framework/Caching/TDbCache.php(552): Prado\Data\TDbCommand->execute()
#1 /var/www/html/vendor/pradosoft/prado/framework/Caching/TDbCache.php(495): Prado\Caching\TDbCache->deleteValue('46f3d3389421db0...')
#2 /var/www/html/vendor/pradosoft/prado/framework/Caching/TCache.php(155): Prado\Caching\TDbCache->setValue('46f3d3389421db0...', Array, 0)
#3 /var/www/html/vendor/pradosoft/prado/framework/TApplicationComponent.php(76): Prado\Caching\TCache->set('prado:applicati...', Array)
#4 /var/www/html/vendor/pradosoft/prado/framework/TComponent.php(503): Prado\TApplicationComponent->getClassFxEvents(Object(Prado\Exceptions\TErrorHandler))
#5 /var/www/html/vendor/pradosoft/prado/framework/TComponent.php(381): Prado\TComponent->listen()
#6 /var/www/html/vendor/pradosoft/prado/framework/TApplication.php(812): Prado\TComponent->__construct()
#7 /var/www/html/vendor/pradosoft/prado/framework/TApplication.php(1162): Prado\TApplication->getErrorHandler()
#8 /var/www/html/vendor/pradosoft/prado/framework/TApplication.php(390): Prado\TApplication->onError(Object(Prado\Exceptions\TDbException))
#9 /var/www/html/index.php(19): Prado\TApplication->run()
#10 {main}

#0 /var/www/html/vendor/pradosoft/prado/framework/Caching/TDbCache.php(552): Prado\Data\TDbCommand->execute()
#1 /var/www/html/vendor/pradosoft/prado/framework/Caching/TDbCache.php(495): Prado\Caching\TDbCache->deleteValue('46f3d3389421db0...')
#2 /var/www/html/vendor/pradosoft/prado/framework/Caching/TCache.php(155): Prado\Caching\TDbCache->setValue('46f3d3389421db0...', Array, 0)
#3 /var/www/html/vendor/pradosoft/prado/framework/TApplicationComponent.php(76): Prado\Caching\TCache->set('prado:applicati...', Array)
#4 /var/www/html/vendor/pradosoft/prado/framework/TComponent.php(503): Prado\TApplicationComponent->getClassFxEvents(Object(TWebSocketModule))
#5 /var/www/html/vendor/pradosoft/prado/framework/TComponent.php(381): Prado\TComponent->listen()
#6 /var/www/html/vendor/pradosoft/prado/framework/Prado.php(354): Prado\TComponent->__construct()
#7 /var/www/html/vendor/pradosoft/prado/framework/TApplication.php(982): Prado\Prado::createComponent('Application.mod...')
#8 /var/www/html/vendor/pradosoft/prado/framework/TApplication.php(1047): Prado\TApplication->internalLoadModule('webSocket')
#9 /var/www/html/vendor/pradosoft/prado/framework/TApplication.php(1072): Prado\TApplication->applyConfiguration(Object(Prado\TApplicationConfiguration), false)
#10 /var/www/html/vendor/pradosoft/prado/framework/TApplication.php(1072): Prado\TApplication->applyConfiguration(Object(Prado\TApplicationConfiguration), false)
#11 /var/www/html/vendor/pradosoft/prado/framework/TApplication.php(1100): Prado\TApplication->applyConfiguration(Object(Prado\TApplicationConfiguration), false)
#12 /var/www/html/vendor/pradosoft/prado/framework/TApplication.php(373): Prado\TApplication->initApplication()
#13 /var/www/html/index.php(19): Prado\TApplication->run()
#14 {main}

#0 /var/www/html/vendor/pradosoft/prado/framework/Caching/TDbCache.php(552): Prado\Data\TDbCommand->execute()
#1 /var/www/html/vendor/pradosoft/prado/framework/Caching/TDbCache.php(495): Prado\Caching\TDbCache->deleteValue('46f3d3389421db0...')
#2 /var/www/html/vendor/pradosoft/prado/framework/Caching/TCache.php(155): Prado\Caching\TDbCache->setValue('46f3d3389421db0...', Array, 0)
#3 /var/www/html/vendor/pradosoft/prado/framework/TApplicationComponent.php(76): Prado\Caching\TCache->set('prado:applicati...', Array)
#4 /var/www/html/vendor/pradosoft/prado/framework/TComponent.php(503): Prado\TApplicationComponent->getClassFxEvents(Object(Prado\TApplicationStatePersister))
#5 /var/www/html/vendor/pradosoft/prado/framework/TComponent.php(381): Prado\TComponent->listen()
#6 /var/www/html/vendor/pradosoft/prado/framework/TApplication.php(872): Prado\TComponent->__construct()
#7 /var/www/html/vendor/pradosoft/prado/framework/TApplication.php(469): Prado\TApplication->getApplicationStatePersister()
#8 /var/www/html/vendor/pradosoft/prado/framework/TApplication.php(1234): Prado\TApplication->loadGlobals()
#9 /var/www/html/vendor/pradosoft/prado/framework/TApplication.php(386): Prado\TApplication->onLoadState()
#10 /var/www/html/index.php(19): Prado\TApplication->run()
#11 {main}

#0 /var/www/html/vendor/pradosoft/prado/framework/Caching/TDbCache.php(552): Prado\Data\TDbCommand->execute()
#1 /var/www/html/vendor/pradosoft/prado/framework/Caching/TDbCache.php(495): Prado\Caching\TDbCache->deleteValue('46f3d3389421db0...')
#2 /var/www/html/vendor/pradosoft/prado/framework/Caching/TCache.php(155): Prado\Caching\TDbCache->setValue('46f3d3389421db0...', Array, 0)
#3 /var/www/html/vendor/pradosoft/prado/framework/TApplicationComponent.php(76): Prado\Caching\TCache->set('prado:applicati...', Array)
#4 /var/www/html/vendor/pradosoft/prado/framework/TComponent.php(503): Prado\TApplicationComponent->getClassFxEvents(Object(Prado\Web\TUrlManager))
#5 /var/www/html/vendor/pradosoft/prado/framework/TComponent.php(381): Prado\TComponent->listen()
#6 /var/www/html/vendor/pradosoft/prado/framework/Web/THttpRequest.php(324): Prado\TComponent->__construct()
#7 /var/www/html/vendor/pradosoft/prado/framework/Web/THttpRequest.php(762): Prado\Web\THttpRequest->getUrlManagerModule()
#8 /var/www/html/vendor/pradosoft/prado/framework/Web/THttpRequest.php(778): Prado\Web\THttpRequest->parseUrl()
#9 /var/www/html/vendor/pradosoft/prado/framework/TApplication.php(1103): Prado\Web\THttpRequest->resolveRequest(Array)
#10 /var/www/html/vendor/pradosoft/prado/framework/TApplication.php(373): Prado\TApplication->initApplication()
#11 /var/www/html/index.php(19): Prado\TApplication->run()
#12 {main}

[belisoful]

It still seems that the cache is not getting set properly and is setting the cache much more than needed. I can imagine the first second of a web server going online, loading all its classes, and there being a collision here or maybe there, but after loading the first time, the code being executed should never be hit, especially in a performance mode.

That's the part that is boggling my mind. Are you running a shared DB cache system?

Could it be that the other instances are clobbering the cache causing the correction to not work properly? If other instances are incorrectly invalidating the shared DB cache, the new code is going to have the same issue.

[belisoful]

I can see how your situation would happen in a shared DB cache environment where other instances are not behaving nicely like the new fix. The other misbehaving servers will thrash the cache despite the fix.

In such a case, the solution is to deploy the micro-fix to all servers in the shared environment. It'll speed things up too.