Symptoms
A VPS-related task fails in Parallels Operations Automation (POA) with the following error message:
Connection to VZAgent was closed: poll_write efds
The same issue may cause inability to login to VZPP with the following error in CP:
There is no host with ID=xxx.
Cause
This is a general error message that indicates a problem with the connection from POA to the Virtuozzo Agent (VZAgent, PVA Agent) on the Parallels Virtuozzo Containers (PVC) server where the container is running.
There are several possible causes:
The PVC server is not available. For example, it has been turned off or some critical error occurred on a server, causing it to hang
The VZAgent service is not running on the PVC server
TCP ports 4433/4434 are closed in the firewall on the PVC server (or on intermediate routers in the datacenter), so POA cannot establish a connection to VZAgent
An unsupported PVC version has been installed
- The root credentials for the PVC server do not correspond with the credentials in the POA database
Resolution
Check the POA VPS Hosting Deployment Guide to ensure a supported PVC version is installed on the PVC server.
Perform these basic operations to find out whether the PVC server is available from POA:
Ping the PVC server from the POA Management Node
Check you can log into the PVC server by SSH/RDP
Use the
telnet
utility on the POA Management Node to check connectivity to ports 22 (SSH) or 3389 (RDP)Use
traceroute
to check the routing path from POA to the PVC server- Use KVM/local console to check the server status if possible
Check if ports 4433/4434 are being listened to locally on the PVC server:
Windows:
> netstat -ano | findstr ":443[34]"
Linux:
# netstat -antp | grep ":443[34]"
Check the status of the VZAgent service on the PVC server and start it if it is not running:
Windows:
> net start | findstr "Agent"
Linux:
# vzagent_ctl status # pvaagent status
Use the basic network utilities on the POA Management Node to check if POA can connect to ports 4433/4434 on the PVC server:
# nmap -P0 <PVC_SERVER> -p 4433,4434 # telnet <PVC_SERVER> 4433 # netcat <PVC_SERVER>:4433 # openssl s_client -connect <PVC_SERVER>:4434 -cipher ADH-AES256-SHA
Replace
<PVC_SERVER>
in the commands above with the IP address or hostname of the PVC server in question.Check/configure firewall rules on the PVC server in accordance with the Parallels Knowledgebase articles: