Flushing cache during deployment on production system in TYPO3 (Composer based installation) - typo3

Question

With a Composer-based TYPO3 installation (in production), when is it necessary to flush caches, and how to do it?
With a non-Composer installation + using the "Extension Manager", the flushing of caches happens automatically when an extension is installed or updated.
What is the equivalent on the command line when updating / deploying?
Is it recommended to do a (hard) cache flush in some (all) cases?
Also, what is the equivalent of doing a flush cache operation in Maintenance mode ("Install Tool") from the command line (including opcache flush)?
Example deployment workflow (this may be done with some tool, such as deployer)
fetch git repository
composer install --no-dev
... other commands to flush cash, update DB schema etc.

Answer 1

Have a look at this extension: https://packagist.org/packages/helhum/typo3-console it allows you to execute commands on your typo3 installations programmatically including one called cache:flush
You can then utilize composer hooks like post-autoload-dump to execute this command. So it might look something like this in your composer.json:
"scripts": {
"post-autoload-dump": [
"typo3cms install:generatepackagestates",
"typo3cms install:fixfolderstructure",
"typo3cms install:extensionsetupifpossible"
"typo3cms cache:flush"
]
}
I can't tell you if it's recommended though as I don't run composer on my production server.

Answer 2

If you add the extensions through composer, but still install (enable) them in the TYPO3 Extension Manager or using typo3_console, the cache will still be automatically flushed. For updated extensions, or if you install the extensions directly in PackageStates.php (through git for example) it is recommended to flush the cache and do a database compare (or extension setup).
As crs says in his answer, you can flush the cache with the typo3_console extension. You can even specify which caches you want to flush using cache:flushcache. You can also do a database compare with that extension from the command line using database:updateschema or extension setup using extension:setupactive (which does the database changes and default configuration for active extensions)

Answer 3

With some delay, I would like to add my setup.
I deploy with deployer now and am using gordalina/cachetool to flush the opcache.
The following snippets are simplified, only the cache flush / post deploy commands are added.
For TYPO3 v11. (it highly depends on the TYPO3 version!!!)
After (or rather during) deployment, composer typo3-post-deploy is run.
composer.json (extract):
{
"requires": {
"gordalina/cachetool": "^7.0.0",
"helhum/typo3-console": "7.1.2"
},
"scripts": {
"typo3-post-deploy": [
"#php vendor/bin/typo3 extension:setup",
"#php vendor/bin/typo3cms database:updateschema",
"#php vendor/bin/typo3cms cache:flush",
"#php vendor/bin/cachetool opcache:reset"
],
"deploy:post": [
"#typo3-post-deploy"
],
"typo3-cms-scripts": [
"#php vendor/bin/typo3cms install:fixfolderstructure"
],
"post-autoload-dump": [
"#typo3-cms-scripts"
],
"cache:flush": [
"#php vendor/bin/typo3cms cache:flush",
"#php vendor/bin/cachetool opcache:reset"
]
}