Re: Help in debugging ACF connection issue

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

Thanks to Ralph for correcting my wording!

There will be a catch if localhost/loopback is explicitly used for CA (EPICS_CA_ADDR_LIST="127.0.0.1") in an IOC : if that IOC has CA links (dbCA links, asCA links, etc.) to other PVs on other hosts, those CA links most likely will never be connected. 

At NSLS-2 Accelerator Controls, we heavily use ACF and we never had such a subtle connection issue so that I am intrigued by this topic. For us, we use EPICS_Subnet_BroadcastIP, something like epicsEnvSet("EPICS_CA_ADDR_LIST", "x.x.x.255"), in every IOC and all softIOCs (Debian or RHEL) are managed by systemd-softioc which assures a softIOC starts only after the network is ready by something like After=network.target in the IOC's systemd service.

Cheers,

Yong

From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Ralph Lange via Tech-talk <tech-talk at aps.anl.gov>
Date: Friday, March 6, 2026 at 10:53 AM

 

On Fri, 6 Mar 2026 at 13:51, Érico Nogueira Rolim via Tech-talk <tech-talk at aps.anl.gov> wrote:

On 3/5/26 14:47, Hu, Yong wrote:

Another thing worthy of checking: If you use systemd, make both IOC services start after network-online.target, to avoid your IOCs start before your NICs/IPs are fully functional.

Should this still matter for IOCs on the same server, since they can send broadcasts on the loopback interface? I even checked the listening sockets opened by each IOC, and they are all opened with 0.0.0.0, so specific network devices shouldn't matter... Still, it might be worth a try.

Keep in mind that CA does not use localhost/loopback by default. (Else the client would always get two replies for a local IOC on a machine with a NIC.) You need to configure CA to use localhost.

 

I always think CA clients will continuously attempt to connect until timeout (EPICS_CA_MAX_SEARCH_PERIOD, 300-second). I am surprised it never connects in your asCa case.

As am I!

That value is - as the name implies -  a maximum search period and *not* a timeout.

CA clients will continuously attempt to connect in increasing intervals. These intervals will increase up to that value.

Cheers,
~Ralph