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Use AWS API Gateway Stage Variables To Call Specific Lambda Aliases

In the previous article, we have specified the version number of the lambda function in the API gateway. In this article, we will use AWS API Gateway stage variables to call specific Lambda aliases.

Create A Lambda Function

The first step is to create the lambda function.

Picture showing creating a lambda function in AWS console

Create The Lambda Function Alias

The next step is to create a lambda function alias.

Picture showing an alias is created in lambda function

Create The Staging Variable

Once the lambda alias is created, create an AWS API gateway. Create the method and the stages. Once the stage is created, go to the Stage variables section.

Picture showing the stage variables section for creating the stage variable

Click on the Edit button. The following page will appear.

Picture showing the add stage variable button for adding the stage variable

Click on the Add stage variable button. A new row is added to enter the key-value pair.

Picture showing adding the stage variable

Click on the Save button. The stage variables are added.

Picture showing the stage variables are added

Specifying The Staging Variable In API Gateway

For specifying the staging variable, we have to use this syntax: -

${stageVariables.[staging_variable_name]}

Picture showing specifying the stage variable in the API gateway

Once you specify the staging variable, a section will appear with the script to be executed using AWS CLI.

Picture showing the CLI command to grant permission for using the stage variable

Scroll down to the bottom and save the data.

Executing Script On CLI

While executing the script, you must change the ${stageVariables.stagevar} with the actual alias name.

aws lambda add-permission --function-name "arn:aws:lambda:ap-south-1:462618770999:function:lambafunc:myalias" --source-arn "arn:aws:execute-api:ap-south-1:462618770999:iv8s88eaw7/*/GET/" --principal apigateway.amazonaws.com --statement-id 0c3f20ef-7652-411c-b82c-8ca69d0fbf70 --action lambda:InvokeFunction

Picture showing the execution of CLI command for granting permission for stage variable

Output

Check the API.

Posted By -	Karan Gupta

Posted On -	Thursday, February 15, 2024

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