Symptoms
A VPS backup/migration task in POA fails with the following error message:
Connection to VZAgent was closed: poll_read efds
Cause
This is a general error message about an inability to connect from the PVC server with a container to the target node of the current operation (e.g., to a backup server to store a backup; or to the target node to migrate the container to) through the TCP ports 4433/4434 -- the operators hwm or backupm of PVC Agent cannot initiate the control connection to start the slave operator on the target node.
Resolution
Perform base connectivity checks from the source PVC server (where the container is running) to the target server, e.g., using the commands below:
# telnet TARGET_SERVER 4433
# netcat TARGET_SERVER:4433
# nmap -P0 TARGET_SERVER -p 4433,4434
# openssl s_client -connect TARGET_SERVER:4434 -cipher ADH-AES256-SHA
The problem may also appear due to routing/firewall reconfiguration during the operation, when the control connection is suddenly lost.
Check/configure firewall rules on PVC servers in accordance with these KB articles:
PVC for Linux - Which ports should be opened on Virtuozzo Hardware Node and Service Container
- PVC for Windows - Which ports should be opened on Virtuozzo Hardware Node and Service Container
After you find and resolve the problem with connectivity between PVC servers, rerun the failed task in POA Task Manager.