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How to Troubleshoot "Remote host closed connection." Errors in RTF For App to App Requests

Publish Date: Jul 21, 2025
Steps

CONTENTS

You are using RTF and for an app to app request, you are seeing the error  "Remote host closed connection.".
  
Remote host closed connection. Possible SSL/TLS handshake issue. Check protocols, cipher suites and certificate set up. Use -Djavax.net.debug=ssl for further debugging.
 

STEPS TO FOLLOW

1. Enable HTTP wire logging: How to Enable HTTP Wire Logging for the HTTP Connector
This will help identify whether the request reached the downstream app or if it even left the 1st app.

2. Setup tcpdumps from perspective of both pods: Run tcpdump on Pod Level in RTF. You may need to engage your infrastructure or vendor support team if you are running on Self Managed Kubernetes.

From the tcpdumps, find out if the request ever reached the 2nd app. If it did, then you would need to continue troubleshooting from the app or policy perspective:
What Logs To Collect For API Policy Case
How to enable trace logging for Mule Policies

3. If this is easily reproducible, try going into pod of both apps to call the 2nd app via curl (in the 2nd app, call via localhost) and see if you can isolate the issue:
 How to Enter the Shell of a RTF App

Otherwise, you may need to setup a load test or wait for a certain window of time to reproduce it.

4. Check if calling the app by the pod name or service name has a different result than calling it via the load balancer and ingress:
How to Send Request to Individual Mule Pod in RTF

5. If it only fails when calling via load balancer and ingress, you will need to engage your infrastructure team or vendor support for the load balancer. If ingress is the issue and you are using Gravity RTF, please enable the ingress TRACE logs: Unable to See Log Level Changes in RTF Appliance Ingress Logs
If you are on Self Managed Kubernetes, you will need to contact your vendor support for assistance on troubleshooting ingress.
Knowledge Article Number

001116493

 
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