Issues with Redis cache Performance

Shashank Juyal 1 Microsoft Employee

A customer is using Azure Redis cache and seem to be facing performance issues. They have around 700 Client connections concurrently and are hosted on Redis Cache P1 Tier. The session id has a time out of 200 Mins. Typically P1 can support around 7500 connections on P1.

They are hitting 100% of their limit quite easily. for example,

Premium P1 can have up to 7500 connections, so their 443 connections were very far way of the limit.
From Azure Cache for Redis performance documentation, we can see the limit of SSL requests is 172000/sec, and we can see in their case the number of operations was 19.66K operations/sec

Any suggestions or guidance on what could probably be leading to this would be really helpful

Anurag Sharma 17,606 Reputation points

2021-09-20T06:54:34.56+00:00

Hi @Anonymous , welcome to Microsoft Q&A forum.

We are checking on this issue internally with product group and shall get back at the earliest.
Anurag Sharma 17,606 Reputation points

2021-09-20T18:41:12.25+00:00

Hi @Anonymous , thanks for your patience. As mentioned they are hitting the 100% limit, is this the client connections limit or CPU usage limit? Also if possible to get the screenshot of the matrix of Connected Clients, CPU Usage, SSL requests etc. it would be easier to understand the issue.
Shashank Juyal 1 Reputation point Microsoft Employee

2021-09-21T04:05:19.25+00:00

Hi Anurag, CPU utilization is hitting 100% with very few connections. I'm referring to below documents for performance limits

https://video2.skills-academy.com/en-us/azure/azure-cache-for-redis/cache-planning-faq#azure-cache-for-redis-performance

Here are the numbers on the cache

CPU Usage = 100%
Operations/per sec = 19K
Connected clients = 443

The cache should not hit 100% of its capacity when number of connections is very low (i.e 19K)
Anurag Sharma 17,606 Reputation points

2021-09-21T08:59:11.567+00:00

Thanks for replying back. Normally the long running commands or more number of requests peak the CPU usage but these stats show we are way below the permissible values. I have passed these details internally already and waiting for response.

Could you also confirm which sdk/technology (Java, .NET etc.) are you using to connect to Azure Redis, so I can try to repro from my side as well?
Shashank Juyal 1 Reputation point Microsoft Employee

2021-09-22T13:22:43.483+00:00

Java

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Issues with Redis cache Performance

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