TYPO3: clear cache by tag for custom content element when record in backend is changed - typo3

Question

I have a sysfolder with records which get displayed in the frontend via a custom content element.
Now I have the problem that the frontend is not updated when a new record is added or an existing record is changed.
To clear the cache I'm using a hook in ext_localconf.php:
$GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['t3lib/class.t3lib_tcemain.php']['clearCachePostProc']['foobar'] =
\Vendor\Name\Hooks\DataHandler::class . '->clearCachePostProc';
The hook looks like this:
<?php
namespace Vendor\Name\Hooks;
use TYPO3\CMS\Core\Cache\CacheManager;
use TYPO3\CMS\Core\SingletonInterface;
use TYPO3\CMS\Core\Utility\GeneralUtility;
class DataHandler implements SingletonInterface
{
public function clearCachePostProc(array $params): void
{
if (isset($params['table']) && $params['table'] === 'tx_foo_domain_model_bar') {
$cacheManager = GeneralUtility::makeInstance(CacheManager::class);
$cacheManager->flushCachesByTag('1642782027');
}
}
}
And the content element is implemented with FLUIDTEMPLATE and a dataprocessor:
tt_content {
foo_bar =< lib.contentElement
foo_bar {
templateName = myTemplate
stdWrap.cache {
key = tx_foo_domain_model_bar
tags = 1642782027
lifetime = default
}
dataProcessing {
10 = TYPO3\CMS\Frontend\DataProcessing\DatabaseQueryProcessor
10 {
table = tx_foo_domain_model_bar
pidInList = {$foo.storage_pid}
as = foobar
}
}
}
}
Everything seems to work but when I hit Cmd+R/Ctrl+R and reload the page or visit it again via the navigation, the page is not updated with the latest content.

Answer 1

I implemented the following solution.
Within the Typoscript Setup add a addPageCacheTag to your custom content element:
tt_content {
foo_bar =< lib.contentElement
foo_bar {
templateName = FooBar
dataProcessing {
10 = TYPO3\CMS\Frontend\DataProcessing\DatabaseQueryProcessor
10 {
table = tx_foo_domain_model_bar
pidInList = {$foo.storage_pid}
as = foobar
}
}
stdWrap.addPageCacheTags = foo_bar
}
}
Add the clearCacheCmd to the Page TSConfig from the storage page like:
TCEMAIN.clearCacheCmd = cacheTag:foo_bar
For testing, add this to your Fluid-Template and be sure to test with a separate browser (without BE login):
<div style="color: red;"><f:format.date format="d.m.Y - H:i:s">now</f:format.date></div>
Kudos to https://daniel-siepmann.de/posts/2019/typo3-content-caching.html

Answer 2

You could use the EXT:Fluid Page Cache
https://extensions.typo3.org/extension/fluid_page_cache
This EXT does all the things you need automatically.