Redis is a caching method which can increase the speed of the backend and frontend of your shop. On Hypernode every customer has access to Redis cache, starting from 64 MB, depending on the plan. This article will explain how to configure Redis on your Magento 2 shop on Hypernode and how to work with redis-cli.

Want to know how to configure Redis in Magento 1? Have a look at this article!

Configure Redis Cache for Magento 2

To enable caching in Redis, extend your /data/web/magento2/app/etc/env.php with the following snippet. Add this in between the cache keys. (Without the cache key in the snippet)

A complete env.php configuration example can be found over here

Now flush your cache:

Configure Redis Full Page Caching for Magento 2

To enable page caching Redis, extend your /data/web/magento2/app/etc/env.php with the following snippet.
You should paste this in between the cache keys, so leave the cache tag in this snippet out of it.

A complete env.php configuration example can be found over here

And flush your cache:

Flush your caches

To flush your Magento cache, clear the Redis database corresponding to your configured Redis database:

Or alternatively use n98-magerun2 or the Magento cli tool:

To flush all sessions, caches etc (flush the full Redis instance), use the following command:

Changing the compression library

It is possible to use the compression library ‘Snappy’ on Hypernode. More information about Snappy can be found in the changelog: Release-4224.

In order to use the compression library Snappy for your Redis cache you need to add 'compression_library' => 'snappy', in your env.php under:

Configure Magento 2 to use Redis as the session store

You can use Redis for storing sessions too! To do so on Magento 2, read the article about storing sessions in Redis and configure your shop accordingly.

Troubleshooting

A quick note, when you run into the configured max memory limit make sure that the necessary Redis keys are set to volatile (ensure an expire). Otherwise the complete allocated configured memory will fill up and Redis will ‘crash’.

When your Redis instance memory is full, and a new write comes in, Redis evicts keys to make room for the write based on your instance’s maxmemory policy. This is called the eviction policy.

In some cases we see that when Redis reaches the configured limit and tries to expire keys to make room, the eviction policy gets stuck in a loop. This means keys won’t be expired and Redis reaches it limit.

A temporary solution is to flush the Redis cache, you can do this by using the flushall command:

This will flush out all available Redis databases. Please keep in mind that this is only a temporary solution. The underlying cause is in the code of your application and needs to be permanently resolved.

A more extended how-to about configuring Redis caches can be found on the Magento help pages.

Bots

As you know, the sessions of your webshop can also be stored in Redis. If you use Redis caching and store the sessions in Redis as well, you’ll have to share the available Redis memory. This shouldn’t be a problem on a regular basis, however we’ve seen scenarios wherein a shop stores its sessions in Redis and had some aggressive bots/crawlers visiting the shop. This resulted in a much larger amount of sessions to be stored in Redis than usual which is causing the Redis memory to fill up in no time, and crashes Redis.

You can check the bot traffic on your shop at any time on MageReport. If you want to get a more detailed insight in the bot traffic you can use the command pnl --yesterday --php --bots --fields ua | sort | uniq -c | sort -n to get an overview of the top 10 bots that visited your webshop yesterday. For more information about abuse bot check our article.

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