CODEWITHSUNDEEP
databaseperformancepostgresqlamazon-web-servicesamazon-rds
RvPr
RvPr

Reputation: 1164

Determining when to scale up my AWS RDS database?

I'm building a web service, consisting of many different components, all of which could conceivably be bottlenecks. I'm currently trying to figure out what metrics I should be looking for, when deciding whether or not my database (on AWS RDS) is the bottleneck in the chain.

Looking at AWS Cloudwatch, I see a number of RDS metrics given. Full list:

  1. CPUCreditBalance
  2. CPUCreditUsage
  3. CPUUtilization
  4. DatabaseConnections
  5. DiskQueueDepth
  6. FreeStorageSpace
  7. FreeableMemory
  8. NetworkReceiveThroughput
  9. NetworkTransmitThroughput
  10. ReadIOPS
  11. ReadLatency
  12. ReadThroughput
  13. SwapUsage
  14. WriteIOPS
  15. WriteLatency
  16. WriteThroughput

The key metrics that I think I should be paying attention to:

  1. Read/Write Latency
  2. CPU-Utilization
  3. Freeable Memory

With the latency metrics, I'm thinking that I should set up alerts if it exceeds >300ms (for fast website responsiveness), though I recognize that this is very much workload dependent.

With the CPU/memory-util, I have no idea what numbers to set these to. I'm thinking I should set an alert for 75% CPU-utilization, and 75% drop in Freeable Memory.

Am I on the right track with the metrics I've shortlisted above, and the thresholds I have guessed? Are there any other metrics I should be paying attention to?

Upvotes: 1

Views: 777

Answers (2)

E.J. Brennan
E.J. Brennan

Reputation: 46859

I think you are on the right track - especially with the latency metrics; for a typical application with database back-end, the read/write latency is going to be what the user notices most if it degrades. Sure the memory or cpu usage may spike, but does any user care? No, not unless it then causes the latency to go up.

I'd start with the metrics you listed as the low-hanging fruit and adjust accordingly.

Upvotes: 1

John Rotenstein
John Rotenstein

Reputation: 269540

The answer is totally dependent on your application. Some applications will require more CPU, some will need more RAM. There is no definitive answer.

The best thing is to monitor your database (with the metrics you list above). Then, when performance is below desired, take a look at which metrics are showing problems. These should be the first ones you track for scaling your database.

The key idea that if your customers are experiencing problems, it should be appearing in your metrics somewhere. If this isn't the case, then you're not collecting sufficient metrics.

Upvotes: 1

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