Volume Services Flapping Due to EADDRINUSE in pf9-comms Service

Problem

The volume provisioning failed intermittently as the Storage services on one or more hosts were observed to be repeatedly transitioning between up and down states, leading to a degraded Persistent Storage Service status.

Environment

• Private Cloud Director Virtualization - v2025.4 and Higher
• Self-Hosted Private Cloud Director Virtualization - v2025.4 and Higher
• Persistent Storage

Cause

The issue was caused by communication socket exhaustion on the affected node, leading to port binding failures. Specifically, the pf9-comms service was repeatedly logging the following error in /var/log/pf9/comms/comms.log:

EADDRINUSE encountered during SNI client creation ... retrying in 20000 milliseconds

This indicates that the required port was already in use or in TIME_WAIT state, preventing successful socket binding and disrupting communication between services (including volume driver interactions with the backend).

Diagnostics

1. The following symptoms were observed:

   • Theopenstack volume service list showed cinder-volume in down state intermittently.
   • The /var/log/pf9/comms/comms.log contained repeated EADDRINUSE errors.

2. The /var/log/pf9/cindervolume-base logs on the cinder host showed API communication failures to the Tintri backend, including:

reached maximum retry attempts: 2, reason: Volume driver reported an error:  (source: CinderDriver, typeId: com.tintri.api.rest.v310.dto.domain.beans.TintriError, code: ERR-API-8001)

Network and Tintri API endpoints were reachable, and credentials were valid, ruling out direct storage backend issues.

Resolution

1. Restarted the pf9-comms service on the affected Cinder volume host:

$ sudo systemctl restart pf9-comms

2. Post-restart, the EADDRINUSE messages no longer appeared in comms.log.
3. The cinder-volume services returned to up state:

$ openstack volume service list -c Binary -c Host -c Status -c State

​

+-----------------+----------------------------------+---------+------+

| Binary          | Host                             | Status  | State|

+-----------------+----------------------------------+---------+------+

| cinder-scheduler| cinder-scheduler-[ID]            | enabled | up   |

| cinder-volume   | [CINDER_HOST_ID]@[CINDER_BACKEND]| enabled | up   |

+-----------------+----------------------------------+---------+------+

4. Verified volume provisioning functionality and ensured that backend API communication was stable.

Validation

• Monitored the cinder-volume service status using the openstack volume service listfor 30 minutes and confirmed that the services remained in the up state.
• No further EADDRINUSE errors were observed in comms.log.
• Volume creation and attachment operations succeeded.

Additional Information

• EADDRINUSE indicates that a socket binding operation failed due to the port already being in use.

• This is often caused by:

  • A large number of short-lived TCP connections
  • Delays in socket cleanup
  • Insufficient ephemeral port ranges or low timeout settings

• Restarting the communication layer (pf9-comms) forces the cleanup of stale sockets and refreshes the SNI client sessions.