Horovod Horovod fails with 'transport endpoint is not connected'

What is Horovod Horovod fails with 'transport endpoint is not connected'

Understanding Horovod

Horovod is an open-source distributed deep learning framework created by Uber. It is designed to make distributed deep learning fast and easy to use. Horovod achieves this by leveraging MPI (Message Passing Interface) or NCCL (NVIDIA Collective Communications Library) for communication between nodes, allowing for efficient scaling of training across multiple GPUs and nodes.

Identifying the Symptom

When using Horovod, you might encounter an error message stating: 'transport endpoint is not connected'. This error typically occurs during the initialization or execution of a distributed training job, causing the process to fail.

Exploring the Issue

The error 'transport endpoint is not connected' indicates a problem with the network connection between the nodes involved in the distributed training. This can happen if the network configuration is incorrect or if there is a disruption in the network connectivity.

Common Causes

Incorrect network configuration or settings. Network hardware issues or failures. Firewall or security settings blocking communication.

Steps to Resolve the Issue

To resolve the 'transport endpoint is not connected' error, follow these steps:

1. Verify Network Configuration

Ensure that all nodes are correctly configured to communicate with each other. Check the network settings and ensure that the IP addresses and ports are correctly set up. You can use the ping command to test connectivity between nodes:

ping

2. Check Network Hardware

Inspect the network hardware such as cables, switches, and routers to ensure they are functioning correctly. Replace any faulty hardware if necessary.

3. Review Firewall and Security Settings

Ensure that the firewall and security settings on each node allow for the necessary communication. You may need to open specific ports used by Horovod and MPI/NCCL. For example, you can use the iptables command to list current rules:

sudo iptables -L

4. Test with a Simple MPI Program

To further diagnose the issue, try running a simple MPI program to verify that the MPI setup is working correctly. This can help isolate whether the problem is with Horovod or the underlying MPI configuration.

Additional Resources

For more information on configuring Horovod and troubleshooting network issues, consider visiting the following resources:

Horovod Documentation Open MPI FAQ NVIDIA NCCL