resource/rds_cluster: Retry modification on InvalidDBClusterStateFault

[radeksimko]

This is to address the following test failure:

=== RUN   TestAccAWSRDSCluster_backupsUpdate
--- FAIL: TestAccAWSRDSCluster_backupsUpdate (110.40s)
    testing.go:428: Step 1 error: Error applying: 1 error(s) occurred:
        
        * aws_rds_cluster.default: 1 error(s) occurred:
        
        * aws_rds_cluster.default: [WARN] Error modifying RDS Cluster (tf-aurora-cluster-4399690208005989315): InvalidDBClusterStateFault: Db Cluster is not available for modifcation with status backing-up
            status code: 400, request id: 96fafc6a-4f48-11e7-a506-eb730ce30037

5 mins is just an arbitrary value which may change if we see failures in the future.

Test results

$ make testacc TESTARGS='-run=TestAccAWSRDSCluster_'
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test $(go list ./... |grep -v 'vendor') -v -run=TestAccAWSRDSCluster_ -timeout 120m
?   	github.com/terraform-providers/terraform-provider-aws	[no test files]
=== RUN   TestAccAWSRDSCluster_importBasic
--- PASS: TestAccAWSRDSCluster_importBasic (123.97s)
=== RUN   TestAccAWSRDSCluster_basic
--- PASS: TestAccAWSRDSCluster_basic (122.37s)
=== RUN   TestAccAWSRDSCluster_namePrefix
--- PASS: TestAccAWSRDSCluster_namePrefix (171.93s)
=== RUN   TestAccAWSRDSCluster_generatedName
--- PASS: TestAccAWSRDSCluster_generatedName (175.72s)
=== RUN   TestAccAWSRDSCluster_takeFinalSnapshot
--- PASS: TestAccAWSRDSCluster_takeFinalSnapshot (127.27s)
=== RUN   TestAccAWSRDSCluster_missingUserNameCausesError
--- PASS: TestAccAWSRDSCluster_missingUserNameCausesError (7.30s)
=== RUN   TestAccAWSRDSCluster_updateTags
--- PASS: TestAccAWSRDSCluster_updateTags (172.02s)
=== RUN   TestAccAWSRDSCluster_kmsKey
--- PASS: TestAccAWSRDSCluster_kmsKey (174.49s)
=== RUN   TestAccAWSRDSCluster_encrypted
--- PASS: TestAccAWSRDSCluster_encrypted (121.68s)
=== RUN   TestAccAWSRDSCluster_backupsUpdate
--- PASS: TestAccAWSRDSCluster_backupsUpdate (147.90s)
=== RUN   TestAccAWSRDSCluster_iamAuth
--- PASS: TestAccAWSRDSCluster_iamAuth (122.09s)
PASS
ok  	github.com/terraform-providers/terraform-provider-aws/aws	1466.747s

[Ninir]

LGTM here!

Left a small non-significant question :)

[Ninir]

What do you think of using the related constant here?

[radeksimko]

We don't actually use constants anywhere else in the provider in this context, but it sounds like a good idea.

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. Thanks!