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Zorluk: OrtaServerless Development with AWS Lambda

A developer is configuring a serverless application where an AWS Lambda function processes messages from an Amazon SQS queue. The Lambda function must also query an Amazon RDS PostgreSQL database located in a private subnet of a VPC.

During testing, the developer observes two issues:
1. Messages are occasionally processed multiple times by the Lambda function, even though the executions complete successfully. The Lambda function's timeout is set to 60 seconds, and the SQS queue's visibility timeout is set to 30 seconds.
2. The Lambda function fails to establish a connection to the RDS database, resulting in connection timeout errors.

Which two actions should the developer take to resolve these issues? (Select two.)

  1. Increase the visibility timeout of the Amazon SQS queue to at least 360 seconds.Cevap
  2. Configure the Lambda function to connect to the VPC using the private subnets, and ensure that the Lambda function's security group allows outbound traffic to the database's security group.Cevap
  3. C
    Configure the Lambda function to run in the public subnets of the VPC and associate a public IP address with the function's execution role.
  4. D
    Decrease the Lambda function's timeout to 15 seconds so that it completes execution before the SQS visibility timeout expires.
  5. E
    Enable SQS FIFO queue deduplication on the existing standard SQS queue to eliminate duplicate messages.

Cevap

To resolve the issues, increase the visibility timeout of the Amazon SQS queue to at least 360 seconds, and configure the Lambda function to connect to the VPC using the private subnets while ensuring the security group allows outbound traffic to the database's security group.
To resolve the duplicate processing issue, the visibility timeout of the SQS queue must be increased. AWS recommends setting it to at least 6 times the Lambda function's timeout (which is 60 seconds, so at least 360 seconds) to ensure that the message remains invisible to other consumers while Lambda processes it. To resolve the database connectivity issue, the Lambda function must be configured with VPC access using private subnets, and its security group must allow outbound traffic to the database's security group.

Adım Adım Çözüm

1
Address the SQS message visibility timeout mismatch by increasing the visibility timeout of the queue to at least 360 seconds (6 times the Lambda function timeout of 60 seconds) to prevent messages from returning to the queue while Lambda is still processing them.
This resolves the issue of messages being processed multiple times due to the function execution duration exceeding the queue's visibility window.
AWS best practices dictate that the SQS visibility timeout should be configured to at least 6 times the Lambda function timeout to avoid duplicate processing and allow for retries.
2
Address the database connection timeout by configuring the Lambda function to access the VPC.
The Lambda function is associated with the private subnets of the VPC and receives Elastic Network Interfaces (ENIs).
To connect to resources in a private VPC subnet like RDS, the Lambda function must be configured with VPC access pointing to private subnets within that VPC.
3
Configure the security groups to allow communication between the Lambda function and the RDS instance.
The Lambda function's security group is allowed outbound access, and the RDS database's security group is configured to allow inbound traffic from the Lambda function's security group.
Network traffic must be explicitly allowed by security groups at both the source (Lambda) and destination (RDS) to establish a successful database connection.

Anahtar Kavram

AWS Lambda integration with Amazon SQS and VPC resources requires proper alignment of SQS visibility timeouts with Lambda timeouts, as well as correct VPC and security group configuration.
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Serverless Development with AWS Lambda

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