Add docs for containerize frames feature

See AcademySoftwareFoundation/OpenCue#1549 for more details

content/docs/Other guides/containerized_frames.md

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+---
+title: "Running RQD at Docker mode"
+linkTitle: "Running RQD at Docker mode"
+weight: 3
+date: 2024-11-06
+description: >
+  Running rqd with docker mode so that each frame is launched
+  at its own container
+---
+
+This guide describes how to configure rqd to run each frame on its own container
+
+## Configuration
+
+The following properties are required on rqd.conf to make use of this feature:
+
+```toml
+[docker.config]
+# Setting this to True requires all the additional "docker.[]" sections to be filled
+RUN_ON_DOCKER=True
+DOCKER_SHELL_PATH=/usr/bin/sh
+
+# This section is only required if RUN_ON_DOCKER=True
+# List of volume mounts following docker run's format, but replacing = with :
+[docker.mounts]
+TEMP=type:bind,source:/tmp,target:/tmp,bind-propagation:slave
+NET=type:bind,source:/net,target:/net,bind-propagation:slave
+
+# This section is only required if RUN_ON_DOCKER=True
+#  - keys represent OSs this rqd is capable of executing jobs in
+#  - values are docker image tags
+[docker.images]
+centos7=centos7.3:latest
+rocky9=rocky9.3:latest
+```
+
+Each key reported under `[docker.images]` will be used as an OS reported to Cuebot by RQD.
+In the example above, rqd will report its OS as `centos7,rocky9`. Whenever cuebot finds a list on
+the OS fields, it will interpret this RQD is capable of launching images for any of the OSs on the list.
+
+## Requirements
+
+The environment your RQD instance is running on needs to have Docker installed and RQD's user needs to
+have permissions to execute docker commands. Besides that, the optional pip requirement `docker` needs
+to be added to requirements.txt.
+
+## Docker swarm setup tips
+
+If you're planning to run RQD itself on docker, docker swarm has some limitations that need to be taken
+into consideration for this setup.
+
+### Docker-in-docker is not recommended
+
+If you want to know the reason why it is not recommend, read this
+[article](https://jpetazzo.github.io/2015/09/03/do-not-use-docker-in-docker-for-ci/).
+ To avoid this scenario, you should mount in docker.sock with
+`--mount type=bind,source=/var/run/docker.sock,target=/var/run/docker.sock,ro`.
+This will give rqd in your container access to the docker daemon running on the host.
+Besides that, your should also run with `--pid=host` because rqd needs access to the
+processes launched from inside of the frame container with their original pid.
+
+But this brings with it one complications. Docker swarm mode doesn't support `--pid=host`
+(See this [Issue](https://github.com/moby/moby/issues/25303)).
+The way around this docker swarm limitation is to create a wrapper service that
+runs RQD using docker run. You service wrapper can be defined as:
+
+```Dockerfile
+FROM docker
+
+COPY docker_wrapper.sh .
+
+ENTRYPOINT "./docker_wrapper.sh"
+```
+
+docker_wrapper.sh
+```bash
+#!/bin/sh
+
+docker pull RQD_IMAGE
+
+# Ensure the last container got removed, as we're creating named containers
+set +e
+docker stop -t $STOP_GRACE_SECONDS rqd
+docker rm rqd
+set -e
+
+
+# Handle SIGINT and SIGTERM and ask the children container to stop respecting its stop_grace period
+handle_exit() {
+    echo "Received a request to terminate"
+    docker stop -t $STOP_GRACE_SECONDS rqd || true
+}
+trap 'handle_exit' INT TERM
+
+
+# Run the rqd container
+exec docker run \
+ --privileged \
+ --rm \
+ --name rqd \
+ --hostname $(hostname) \
+ --pid host \
+ --publish mode=host,target=8444,published=8444 \
+ --mount type=bind,source=/tmp,target=/tmp,bind-propagation=slave \
+ --mount type=bind,source=/var/run/docker.sock,target=/var/run/docker.sock,ro RQD_IMAGE
+```
+
+This wrapper does the bare minimum to make your rqd container behave similarly to a docker
+swarm service when it comes to reacting to `docker service update` commands. Change it
+accordingly if you need to add additional functionalities.