how to dynamically set table name in dynamodb using serverless and DynamoDBContext?

Question

We need to be able to set table name based on build environment. Consider the following class:

[DynamoDBTable("movies")]
public class Movie
{
    [DynamoDBHashKey]
    public string Title { get; set; }

    [DynamoDBRangeKey(AttributeName = "Released")]
    public DateTime ReleaseDate { get; set; }

    public List<string> Genres { get; set; }
}

In serverless.yml, can the table name be set like this:

functions:
    update-movies:
        environment:
            tableName: movies-prod

Then in the code we can load the table name dynamically based on the table name in the tableName variable. We prefer to use DynamoDBContext rather than DynamoDBv2.DocumentModel (which already has a solution here How do I dynamically change dynamodb tablename in c# using object persistence model)

Something like this in Java: https://medium.com/@onclouds/aws-lambda-use-different-dynamodb-tables-for-different-stages-5eda9f5378b2

Did you actually ask a question? How to Ask Your questions reads as a set of requirements — user585968
– user585968, Commented Sep 20, 2018 at 7:35

Tung Nguyen · Accepted Answer · 2018-09-21 01:43:12Z

15

Found a solution by passing a table name prefix:

DynamoDBContextConfig config = new DynamoDBContextConfig()
{
    TableNamePrefix = "prod-"
};

_dynamoDBContext = new DynamoDBContext(new AmazonDynamoDBClient(), config);

You still have to name your table movies though:

[DynamoDBTable("movies")]
public class Movie

DynamoDBContext will add the prefix to the table name when loading the context. So it will try to load prod-movies, stag-movies.

Here is where the table prefix is used in AWS SDK internally

if (!string.IsNullOrEmpty(flatConfig.TableNamePrefix))
    tableName = flatConfig.TableNamePrefix + tableName;

(https://github.com/aws/aws-sdk-net/blob/b691e46e57a3e24477e6a5fa2e849da44db7002f/sdk/src/Services/DynamoDBv2/Custom/DataModel/ContextInternal.cs)

Some references that helped me find the solution:

https://aws.amazon.com/blogs/developer/enhancements-to-the-dynamodb-sdk/

https://github.com/aws/aws-sdk-net/blob/b691e46e57a3e24477e6a5fa2e849da44db7002f/sdk/test/Services/DynamoDBv2/UnitTests/Custom/DynamoDBTests.cs

answered Sep 21, 2018 at 1:43

Tung Nguyen

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1 Comment

Saket Kumar Over a year ago

Can we not remove [DynamoDBTable("movies")] attribute and use the full table name in TableNamePrefix ?

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