How to record and stream video from multiple ip cameras, preferably with node.js?

Question

CCTV

The essence of the problem:
You need to record video from 4 ip-cameras to disk, small files, and at the same time you need the ability to turn on broadcasting to the server. Controlled with Raspberry pi 3 cameras, connected via usb modem to the internet (gray-ip).
Found options:
WebRTC - no recording to disk, the server cannot connect to the camera (gray-ip);
run avConv/ffMpeg separately for writing to disk and separately for broadcasting to the server via TCP/UDP/RTCP - performance problems, control problem (is there enough speed, is there an error).
avConv/ffMpeg and child_process.spawn:
- run avConv with output to a pipe
- node catches stdout and disposes of it as needed, uploading it to a file, or to the server (the server itself deals with the organization of the translation).
But it doesn’t work that way to start the rest of the cameras, as I understand it, there is only one stdout for all child processes. Switching to a new file also fails without a "space" while avConv is running.
Please tell me how this can be done, and if there are alternative solutions.
UPD:
to record from camera to disk I use:
ffmpeg -i input -v warning -c copy -map 0 -f ssegment -strftime 1 -segment_time 10 -segment_format mpeg
documentation with examples

Answer 1

Use NVR instead of rpi3. I did not understand the wording "the ability to include broadcast to the server."