Lambda function error messages

VPC configuration issues

VPC configuration issues can raise the following error messages when trying to connect:

ERROR:  invoke API failed
DETAIL: AWS Lambda client returned 'Unable to connect to endpoint'.
CONTEXT:  SQL function "invoke" statement 1

A common cause for this error is improperly configured VPC security group. Make sure you have an outbound rule for TCP open on port 443 of your VPC security group so that your VPC can connect to the Lambda VPC.

If your DB instance is private, check the private DNS setup for your VPC. Make sure that you set the rds.custom_dns_resolution parameter to 1 and setup AWS PrivateLink as outlined in Step 1: Configure your RDS for PostgreSQL DB instance for outbound connections to AWS Lambda. For more information, see Interface VPC endpoints (AWS PrivateLink).

Lack of permissions needed to invoke Lambda functions

If you see either of the following error messages, the user (role) invoking the function doesn't have proper permissions.

ERROR:  permission denied for schema aws_lambda

ERROR:  permission denied for function invoke

A user (role) must be given specific grants to invoke Lambda functions. For more information, see Step 6: Grant other users permission to invoke Lambda functions.

Improper handling of errors in your Lambda functions

If a Lambda function throws an exception during request processing, aws_lambda.invoke fails with a PostgreSQL error such as the following.

SELECT * FROM aws_lambda.invoke('aws_lambda_arn_1', '{"body": "Hello from Postgres!"}'::json);
ERROR:  lambda invocation failed
DETAIL:  "arn:aws:lambda:us-west-2:555555555555:function:my-function" returned error "Unhandled", details: "<Error details string>".

Be sure to handle errors in your Lambda functions or in your PostgreSQL application.