CAS: Client accept error: Too many open files

["Hu, Yong via Tech-talk" <tech-talk at aps.anl.gov>]

Hi all,

I recently encountered an issue with a misbehaving Linux softIOC that caused Phoebus / CS-Studio to appear broken when opening certain OPIs.

Symptoms: The IOC was periodically logging the following error: CAS: Client accept error: Too many open files.

Whenever I opened an OPI containing PVs from that IOC, all CSS OPI screens turned pink, and all PVs appeared disconnected. However:

• caget and camonitor returned correct PV values.

• The CSS "Probe" tool also displayed PV values normally.

Troubleshooting: I traced the problematic IOC (xxx.x.xxx.xxx:38841) based on terminal output during the failure. The logs included the following error:

SEVERE [Thread 55] com.cosylab.epics.caj.CAJContext (getTransport) - Failed to create transport for: /xxx.x.xxx.xxx:38841

com.cosylab.epics.caj.impl.ConnectionException: Failed to connect to '/xxx.x.xxx.xxx:38841'.

    at com.cosylab.epics.caj.impl.CAConnector.connect(CAConnector.java:138)

    at com.cosylab.epics.caj.CAJContext.getTransport(CAJContext.java:1559)

Rebooting the IOC resolved the issue — at least temporarily.

Looking for Insight: A Google search didn’t yield much, so I asked ChatGPT, which suggested that a shared CA context might lead to a shared failure. That seems plausible, but I’d appreciate input from anyone familiar with Phoebus or CSS internals. Why would OPI screens appear completely broken while the "Probe" tool continues to retrieve PV values correctly?

Thanks in advance for your insights.

Yong