Whats the purpose of the ctx context.Context parameter for config.LoadDefaultConfig

[tomHaum]

Does this need to be a request scoped context?

All the examples i have found in documents show either context.Background() or context.TODO(). I feel like context.TODO() would imply that this should be a request scoped context, but the example code just doesnt support a ctx parameter.

We are utilizing https://github.com/aws/aws-lambda-go and are trying to figure out if the context we pass to the config.LoadDefaultConfig call needs to come from lambda.Start. Are there any special middleware behind the scene that is set and then utilized that we need to ensure still gets passed?

[bhavya2109sharma]

Hello @tomHaum,

Thanks for reaching out.
Regarding your first paragraph, I couldn't fully understand your question about context.Background() and context.TODO(). Could you please provide more details on the specific context usage you're referring to?

To clarify the context handling in your Lambda function:
The context you should use throughout your Lambda function is the one that is passed to the Lambda handler function by the Lambda runtime. This context contains relevant information about the current invocation.

Do let me know if you have any questions.

Thanks,
Bhavya

[tomHaum]

There are three main was functions I'm interested in.

1: config.LoadDefaultConfig
2: dynamodb.NewFromConfig
3: lambda.Start

For 2, I'll use dynamodb as an example but I think this would apply to any aws service defined in this repo

I would like to have my main function of my go application set up a singleton service for dynamodb. The call to dynamodb.NewFromConfig would use a config obtained via passing context.Background to config.LoadDefaultConfig.

I understand that there is additional metadata embedded in context.Context usually, but does any of that modify the config in a substantial way?

Does the context provided to my handler function in say lambda.Start have metadata that would affect the aws.Config that is produced by config.LoadDefaultConfig?

When making the actual call to the service the appropriate context from the lambda will be passed to this singleton service, but the creation of the service would not.

[bhavya2109sharma]

Hello @tomHaum

Thanks for explaining.

• The lambda.Start function is used to start a AWS Lambda function handler and the context provided to the Lambda function handler (the one you passing to lambda.Start) contains metadata about the current execution.

• Therefore, the context provided to the Lambda function handler does not affect the aws.Config produced by config.LoadDefaultConfig. The context is primarily used for logging,making API calls , etc. within the Lambda function execution , but not for configuring the AWS SDK itself.

-Moreover, with respect to your example, the context.Context is only relevant when making the actual DynamoDB API calls, not when setting up the client.

Here is an example code :

func init() {
    // Loading the default AWS configuration
    cfg, err := config.LoadDefaultConfig(context.Background())
    if err != nil {
        panic(err)
    }

    // Creating DynamoDB client from the configuration set above.
    DynamoDBClient = dynamodb.NewFromConfig(cfg)
}

func HandleRequest(ctx context.Context) error {
    // Using the context when making DynamoDB API calls
    output, err := DynamoDBClient.ListTables(ctx, &dynamodb.ListTablesInput{})
    if err != nil {
        panic(err)
    }

    fmt.Printf("DynamoDB tables: %v\n", output.TableNames)
    return nil
}

func main() {
    lambda.Start(HandleRequest)
}

Thanks,
Bhavya