Connecting to Redis cache for thumbnail images

EDSC infrastructure has an elasti-cache instance that can be connected to via EC2 instance. Once connected developers can view cache keys/values, delete keys, or reassign them

Create EC2 Instance

In order to connect to the cache you need to create an EC2 instance to connect to, where you will connect to elasti-cache

To create your EC2 instance, requirements can be found on this wiki page.

Be sure you select a t2.medium instance type, and add the private application subnet in order to connect.

You will then need to add the necessary security groups to your EC2 instance to enable communication to Elasti-Cache. Look for the security groups with "RedisSecurityGroup" and "LambdaSecurityGroup" in the name and add them to your instance.

To connect start up an EC2 instance utilizing AWS linux of at least medium size (NGAP requirement not ours) 

Install the redis-cli tool

$ sudo yum clean metadata
$ sudo yum install redis6 

Note this is if you are using the AWS Linux 2023 image for the EC2 instance

Connect to Elasti-Cache from EC2 Instance

You will need to lookup the host and Port values for the elast-cache instance. The easiest way to do this is search for the Service on Console Elasti-cache  find the cluster instance navigate down to the single node and then copy the host and port value (Note: The value in the Host contains the port so you'll need to split these up in the CLI command below)

To connect to Elasti-cache using the redis-cli:

$ redis6-cli -h=HOST_VALUE -p=PORT_VALUE

Remove/Edit Keys From Cache Instance

For normal operations you should never need to do this, if someone has updated a thumbnail in metadata and they do not want the cache key to expire (Maximum of 24 hours) we could delete the Key from the cache manually. More commands can be found on Redis docs

Elasti-Cache-Instance> KEY <pattern or wildcard for all>
Elasti-Cache-Instance> DEL <Exact key or array of keys>