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Difficulty: MediumHigh-Performing and Elastic Compute Solutions

An energy grid operator runs a distributed power-flow optimization simulator on a fleet of Amazon EC2 instances. The simulator nodes must communicate with each other using Message Passing Interface (MPI) with the lowest possible latency. The optimization service on each instance runs on port 7001. A Network Load Balancer (NLB) distributes management API requests to the instances, but currently reports all instances as unhealthy because the health check is set to the default port 80. Which configuration will achieve the required network performance and resolve the health check issue?

  1. A
    Configure a partition placement group for the EC2 instances. Update the NLB target group health check port to 7001.
  2. B
    Configure a cluster placement group for the EC2 instances. Keep the target group health check port at the default port 80.
  3. Configure a cluster placement group for the EC2 instances. Update the NLB target group health check port to 7001.Answer
  4. D
    Configure a spread placement group for the EC2 instances. Update the NLB target group health check port to 7001.

Answer

Configure a cluster placement group for the EC2 instances. Update the NLB target group health check port to 7001.
For tightly-coupled MPI applications requiring low latency, a cluster placement group is the appropriate choice because it physically groups the instances together inside a single Availability Zone. Additionally, because the application is listening on port 7001, the health check port must be updated from the default port 80 to port 7001 so the load balancer can verify the actual application status instead of getting connection timeouts on an unused port.

Step-by-Step Solution

1
Analyze the latency and network performance requirements for the node-to-node communication.
Determine that the MPI-based application requires a cluster placement group to achieve the lowest possible node-to-node latency.
Cluster placement groups launch instances in a single Availability Zone on shared underlying hardware to support high-throughput, low-latency communication.
2
Identify the cause of the Network Load Balancer marking the EC2 instances as unhealthy.
Detect a port mismatch between the application (port 7001) and the target group health check configuration (default port 80).
Because the application is not listening on port 80, TCP connection attempts from the NLB fail, leading to unhealthy target status.
3
Combine the correct placement group strategy with the health check modification.
Deploy the instances in a cluster placement group and update the target group health check port to 7001.
This resolves the network performance requirements while ensuring the NLB can successfully monitor application availability.

Key Concept

Selecting the correct EC2 placement group for low-latency node-to-node communication and ensuring that the load balancer health check configuration aligns with the application port.
Estimated Time:2m 0s
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High-Performing and Elastic Compute Solutions

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