How to Solve This Error in AWS DMS Serverless?

Question

I am currently facing an issue with AWS Database Migration Service (DMS) Serverless and need some assistance. Below are the details:

I receive the following failure message after started the serverless replication instance:
```
Test connection failed for endpoint '#####' and replication config '#####'. Failure Message: 'Test Endpoint failed: Application-Status: 1020912, Application-Message: Failed to connect to database.'
```

(**Note:** The endpoint name  and replication config  have been redacted by ##### for privacy.)

**Steps Taken:**
**1. Tested Endpoints:**  Verified that both the source (MySQL RDS DB) and target (S3) endpoints were tested successfully.

**2. S3 Bucket Configuration:**
* Confirmed that the S3 bucket configuration is correct.

**3. Checked IAM Role and Policies:**
* Reviewed the S3 IAM role and its attached policy.
* Verified the trust relationship policy associated with the IAM role.

**Additional Information:**
**Source Database:** MySQL RDS DB
**Target:** S3

Despite these checks, the connection continues to fail. I would appreciate any guidance or suggestions on how to resolve this issue.

Thank you!

subhashr · Answer

I assume that this is dms connectivity issue to s3 on private network.

Starting DMS version 3.4.7 DMS must access the source bucket through a VPC endpoint or a public route.

https://docs.aws.amazon.com/dms/latest/userguide/CHAP_Target.S3.html#CHAP_Target.S3.Prerequisites

Unlike replication instances, AWS DMS Serverless replications do not have a public IP address for management tasks 
https://docs.aws.amazon.com/dms/latest/userguide/CHAP_Serverless.Limitations.html

thus having VPC endpoint is a must.

https://docs.aws.amazon.com/dms/latest/userguide/CHAP_VPC_Endpoints.html

this link should give insight on how to create a vpc endpoint to access s3 bucket on private network.

Once you have a VPC endpoint setup, make a note of subnets which would be using this vpc endpoint.

say you 3 VPC subnets. Next is create a AWS DMS replication subnet group with this 3 subnets.

Now while setting up DMS serverless replication config use this DMS replication subnet group.

this should resolve the endpoint connection issue.

for reference you can check the blog https://aws.amazon.com/blogs/database/orchestrate-an-aws-dms-serverless-replication-task-using-aws-cli/

How to Solve This Error in AWS DMS Serverless?

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