Elastic Beanstalk部署Django应用遇RDS InvalidParameterCombination错误

Let's break down your two questions and walk through practical solutions for each issue:

1. Why is 15GB of storage suddenly failing? #

The invalid storage size error comes down to updated AWS RDS parameter rules that kick in when modifying existing instances. Here's the breakdown:

• When you first created your RDS instance, AWS allowed 15GB of standard storage for PostgreSQL 9.5. But AWS periodically adjusts minimum storage requirements for database engines—for most regions and standard storage types, PostgreSQL now requires a minimum of 20GB (or higher) for new/modified instances.
• Your existing instance was "grandfathered" under the old rules, so it ran smoothly until you tried to push changes via eb deploy. When Elastic Beanstalk triggers an RDS configuration update, it uses the latest validation rules, which now reject the 15GB size that was previously allowed.

2. Why is it trying to "upgrade" from PostgreSQL 9.5.10 to 9.5.4? #

This is a misleading error message from AWS—what’s actually happening is a configuration mismatch:

• Your Elastic Beanstalk environment is set to use PostgreSQL 9.5.4, but your live RDS instance is running 9.5.10 (a newer minor version).
• When you run eb deploy, EB tries to sync the RDS instance to match the version specified in its settings. Since 9.5.4 is older than 9.5.10, this is a downgrade attempt—not an upgrade. PostgreSQL doesn’t allow downgrading minor versions (they’re cumulative updates with no rollback path), which triggers the error.

Recommended Solutions #

Fix the storage size issue #

1. First, confirm the minimum storage requirement for your PostgreSQL version and region:
   • Check via the AWS RDS console (create a test instance and look at the storage slider’s minimum value) or run this CLI command:

     aws rds describe-db-engine-versions --engine postgres --engine-version 9.5.10 --query 'DBEngineVersions[0].ValidStorageOptions'
     

2. Update your EB configuration to set the storage size to a value that meets the current minimum (e.g., 20GB or higher). You can do this in:
   • Your .ebextensions config file (look for the DBStorage parameter)
   • The EB console under Configuration > Database > Storage
   • Via EB CLI with eb config (edit the DBStorage value directly)

Fix the version mismatch issue #

1. Align your EB configuration with the actual RDS version:
   • Find where you specified the PostgreSQL version in your EB setup (.ebextensions, console settings, or CLI config) and update it to 9.5.10 to match your live RDS instance.
2. Long-term: Upgrade to a supported PostgreSQL version:
   • PostgreSQL 9.5 reached end-of-life in February 2021, and AWS has likely stopped supporting it for new configurations. Upgrading to a newer maintained version (e.g., 12+) will prevent future compatibility issues with AWS RDS and Elastic Beanstalk updates.

内容的提问来源于stack exchange，提问作者creimers