modify-instance.sh

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Purpose

Apply controlled mutable configuration changes to an existing AWS RDS DB instance.

Location

cloud/aws/rds/modify-instance.sh

Preconditions

  • Required tools: bash, aws, date, sleep
  • Required permissions: rds:ModifyDBInstance, rds:DescribeDBInstances
  • Required environment variables: none

Arguments

Flag Required Default Description
--identifier ID Yes N/A DB instance identifier
--instance-class CLASS No unchanged New instance class
--allocated-storage GB No unchanged New storage size
--storage-type TYPE No unchanged Storage class
--iops N No unchanged Provisioned IOPS
--backup-retention-days N No unchanged Backup retention days
--maintenance-window WINDOW No unchanged Preferred maintenance window
--backup-window WINDOW No unchanged Preferred backup window
--ca-certificate-id ID No unchanged CA certificate rotation target
--multi-az / --no-multi-az No unchanged Multi-AZ toggle
--auto-minor-version-upgrade / --no-auto-minor-version-upgrade No unchanged Minor upgrade policy
--deletion-protection / --no-deletion-protection No unchanged Deletion protection policy
--apply-immediately No false Apply now instead of maintenance window
--wait No false Wait for available state
--timeout SEC No 7200 Wait timeout
--poll-interval SEC No 20 Poll interval
--region REGION No AWS config Region override
--profile PROFILE No AWS config Profile override
--dry-run No false Print command only

Scenarios

  • Happy path: scale instance class and retention policy with maintenance-safe rollout.
  • Common operational path: scheduled right-sizing or CA rotation during ops window.
  • Failure path: no mutable flags provided or invalid window format.
  • Recovery/rollback path: reapply previous known-good settings.

Usage

cloud/aws/rds/modify-instance.sh \
  --identifier app-prod-db-01 \
  --instance-class db.r6g.large \
  --backup-retention-days 14 \
  --deletion-protection \
  --wait

cloud/aws/rds/modify-instance.sh \
  --identifier app-stg-db-01 \
  --allocated-storage 200 \
  --apply-immediately

Behavior

  • Main execution flow:
  • validates target instance exists
  • ensures at least one mutable change flag is provided
  • builds modify-db-instance request from provided flags
  • optionally applies immediately
  • optionally waits until status returns to available
  • Idempotency notes: mostly idempotent when desired values already match current config.
  • Side effects: may trigger reboot/failover depending on changed attributes.

Output

  • Standard output format:
  • stderr: timestamped logs
  • Exit codes:
  • 0 success
  • 2 validation/precondition errors
  • non-zero on AWS/API/wait failures

Failure Modes

  • Common errors and likely causes:
  • invalid maintenance/backup window syntax
  • unsupported class/storage transition
  • IAM deny on modify action
  • Recovery and rollback steps:
  • correct input and rerun
  • roll back to prior class/storage values
  • schedule changes in maintenance window when needed

Security Notes

  • Secret handling: no secret inputs required.
  • Least-privilege requirements: scope modify permissions to approved DB resources.
  • Audit/logging expectations: changes should be tied to approved operational tickets.

Testing

  • Unit tests:
  • no-op guard and flag validation
  • window format validation
  • Integration tests:
  • non-production class/retention updates
  • Manual verification:
  • validate post-change status, settings, and event stream in RDS
snapshot-restore.sh rds-healthcheck.sh