If you experience a slower webshop after upgrading, follow below steps:
- Use MageReport to see if Redis memory use is lower than normal and not filling up, and check if this corresponds with higher CPU usage and other performance issues. If so, this could indicate you are experiencing this issue
- Check the nginx error.log in /var/log/nginx if the below error is present
Cannot instantiate interface Magento\Framework\App\Config\ConfigSourceInterface in /data/web/magento2/vendor/magento/framework/ObjectManager/Factory/Dynamic/Developer.php:73
- If so, remove Redis default (system) config from env.php
- Switch to production mode (when in development mode)
- After compilation add Redis config back into env.php
- Flush caches (magerun2 cache:flush ; redis-cli flushall)
- (Optional: switch back to development)
Another option is to update the Redis client via Composer, but this can cause complications as not all minimum requirements could be met.
At this moment we do not advice our customers to switch back to 2.1.7, as 2.1.8 solves a few bugs that were present in the earlier release.