Re: How can I get a PV from an external server from inside a docker container?

[Florian Feldbauer via Tech-talk <tech-talk at aps.anl.gov>]

Title: Re: How can I get a PV from an external server from inside a docker container?

Hey,

Am 26.03.2024 um 21:49 schrieb Érico Nogueira Rolim:

On 26/03/2024 15:08, Florian Feldbauer via Tech-talk wrote:

Hey,

just for completeness, if you know the IP addresses of all your IOCs you can also use the default docker network and set the Environment variables
EPICS_CA_AUTO_ADDR_LIST no
EPICS_CA_ADDR_LIST <list of all CA server IP addresses>

In this case, the udp broadcast part of CA seems to be omitted and CA checks the list of IPs directly.

You can also combine them, so EPICS_CA_AUTO_ADDR_LIST=YES so hosts reachable by broadcast Just Work, and EPICS_CA_ADDR_LIST for when it isn't an option (this is relevant when outside of containers as well).

At least this worked in my very first tests with containerization of our clients (Archiver, Alarm system, .....)
But of course this approach is rather error prone and you need to change your config every time an IP address changes/is being added.

If you want to avoid running your IOC with "network_mode: host", IIRC you can also try adding the broadcast address (last address of the netmask) of your relevant network interfaces to EPICS_CA_ADDR_LIST. That way the CA client doesn't need to enumerate the interfaces in order to find them out, but you also don't need a static knowledge of all IOC hosts.

    but broadcasts do not get forwarded from the virtual docker network
    to the physical one, so setting EPICS_CA_ADDR_LIST to the "external"
    broadcast address does not work.

On the other hand, this is the only way I know of if running docker in rootless mode.

Does rootless docker not support setting the network to host mode? I'd strongly recommend podman for that use case, then. IMHO it does a much better job at the "rootless container" need for multiple reasons, including supporting host network mode without any issues.

    Rootless docker (as well as podman according to my tests) do not
    support network_mode host or MACVLAN. So the IOC inside the
    container is not able to send UDP broadcasts to the external
    network.

Cheers,
Florian

Am 26.03.2024 um 09:59 schrieb Carsten Winkler via Tech-talk:

Hello Dale, hello Florian,

many thanks for your helpful advises. Now I could solve the issue simply by adding "network_mode: host" to the service "epicsbase".

Now my working docker-compose.yml  looks like:

services:
    epicsbase:
       image: softioc
       container_name: epicsbase
       volumes:
          - ./epicsbase/db:/usr/local/db
       working_dir: /usr/local/epics
       command:
          - /bin/sh
          - -c
          - |
          echo start first Soft IOC
          screen -d -m /usr/local/epics/epics-base/bin/linux-x86_64/softIoc -D /usr/local/epics/epics-base/dbd/softIoc.dbd -d /usr/local/db/test.db
          tail -f /dev/null # keep alive

       network_mode: host

Best regards
Carsten

--------------------Ursprüngliche Nachricht--------------------
Von: Carsten Winkler <carsten.winkler at helmholtz-berlin.de>
Gesendet: Montag 25. März 2024 14:55
An: tech-talk at aps.anl.gov
Betreff: How can I get a PV from an external server from inside a docker container?

Hello,

I have 3 SoftIOCs.
    1.) local host       = 193.100.100.100 with PV: "local_pv"
    2.) external host  = 192.200.200.200 with PV: "external_pv"
    3.) docker container    on local host   with PV: "docker_pv"

From local host I can read all PVs (caget local_pv external_pv docker_pv). 👍
From inside the docker container I can read the local_pv and the docker_pv
but not the external_pv. 🤔

Here is my docker compose configuration:

services:
    epicsbase:
       image: softioc
       container_name: epicsbase
       volumes:
          - ./epicsbase/db:/usr/local/db
       working_dir: /usr/local/epics
       command:
          - /bin/sh
          - -c
          - |
          echo start first Soft IOC
          screen -d -m /usr/local/epics/epics-base/bin/linux-x86_64/softIoc -D /usr/local/epics/epics-base/dbd/softIoc.dbd -d /usr/local/db/test.db
          tail -f /dev/null # keep alive
       networks:
          - ioc-net
networks:
    ioc-net:

From inside the docker container I have also already tried EPICS_CA_AUTO_ADDR_LIST / EPICS_CA_ADDR_LIST. Unfortunately without success.
With and without these environment variables I only get the local_pv and the docker_pv.

How can I also read the external_pv from inside the docker container?

Best regards
Carsten

-- 
Ruhr-Universität Bochum
AG der Experimentalphysik I
Dr. Florian Feldbauer
NB 2/131 / Fach 125
Universitätsstr. 150
D-44801 Bochum

Office: NB 2/134
Phone:  (+49)234 / 32-23563
Fax:    (+49)234 / 32-14170
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-- 
Ruhr-Universität Bochum
AG der Experimentalphysik I
Dr. Florian Feldbauer
NB 2/131 / Fach 125
Universitätsstr. 150
D-44801 Bochum

Office: NB 2/134
Phone:  (+49)234 / 32-23563
Fax:    (+49)234 / 32-14170
https://paluma.ruhr-uni-bochum.de