Connection Issues with ElastiCache Serverless for Redis on Large Data Packets Using Predis with SSL

Question

I'm facing issues trying to connect and send data to an ElastiCache Serverless for Redis instance using the Predis library in PHP. Specifically, when attempting to send data packets around 20kb, I encounter the following errors:

ERROR: fgets(): SSL: Connection reset by peer
    Error while writing bytes to the server.

I'm using SSL connections to ensure data security, but it seems that when sending larger packets, the connection is interrupted or reset.

Additionally, I would like to clarify whether it's necessary to enable cluster mode in Predis to effectively use ElastiCache Serverless for Redis, even though my application is not explicitly configured to use Redis in cluster mode.

Here are some additional details about my configuration:

Use of the Predis library for Redis connection.
    Connection via SSL to ensure security.
    Attempts to send data packets of approximately 20kb result in errors.
    Uncertainty about the need to enable cluster mode in the Predis configuration for ElastiCache Serverless.

Subram V · Answer

ElastiCache Serverless has a maximum limit of 4000 arguments per request. Crossing this limit can trigger "Connection reset by peer" errors on the Redis client. This is also addressed in our [docs](https://docs.aws.amazon.com/AmazonElastiCache/latest/red-ug/RedisConfiguration.html#RedisConfiguration.Serverless). Check if this is what is happening in your case.

```
Key name length - 4 KiB	(The maximum size for a single Redis key or channel name. Clients referencing keys larger than this will receive an error.)
```

> Additionally, I would like to clarify whether it's necessary to enable cluster mode in Predis to effectively use ElastiCache Serverless for Redis, even though my application is not explicitly configured to use Redis in cluster mode.

Yes, even though the [proxy layer](https://docs.aws.amazon.com/AmazonElastiCache/latest/red-ug/WhatIs.corecomponents.html#WhatIs.HowELCworks) implementation in Serverless makes it look like your application is talking to a single endpoint, the client is still expected to be cluster-aware. For example all the keys in a multi-key operation are expected to be in the same hash slot, if not you will hit the same [CROSSSLOT error](https://repost.aws/knowledge-center/elasticache-crossslot-keys-error-redis#) seen in Cluster Mode Enabled clusters.

Connection Issues with ElastiCache Serverless for Redis on Large Data Packets Using Predis with SSL

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