RDS Missing Cloudwatch Metrics + Too many open files

Question

We're currently experiencing an issue with our RDS instance, where the cloudwatch dashboard is only reporting CPU for the instance (no metrics for database connections, ReadIOPS, WriteIOPS, etc).   
  
We're also seeing a large number of errors in the logs like:   
2021-08-02 15:28:26 UTC::@:\[74500]:LOG:  could not open log file "/rdsdbdata/log/error/postgresql.log.2021-08-02-15": Too many open files in system  
  
This is a db.r4.8xlarge postgresql instance. I'm not quite sure why cloudwatch isn't showing any metrics for this, but I have a feeling it's likely related to the open files issue. This is relatively high priority for us, so any help is appreciated.

Answer

For what it's worth, we ended up lowering the `max_files_per_process` for postgres, which resolved the issue with file descriptors, and everything seemed to start working again.

RDS Missing Cloudwatch Metrics + Too many open files

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