So, I’ve been expanding the testbed I use for my Ethernet/IP I/O module, specifically to simultaneously test the major Ignition versions the module supports. So I created a project that is set up to run on multiple gateway VMs, where the gateways are communicating with each other at high speed in a ring. The v7.7.8 gateway is a slave to a scanner in the v7.8.4 gateway, which is itself a slave to the scanner in the v7.9.1 gateway, and the v7.9.1 gateway is a slave to the v7.7.8 gateway. All of the gateways have the same project and same driver setup, with only the IP addresses varying.
Input and output packets are flying around the ring in both directions, with each server inserting task timestamps and count values in its outbound packets so the synchronization is easy to see from any gateway’s client. The setup uses 100ms RPI (requested packet interval) settings for the Ethernet/IP I/O scanners in all three gateways, and the gateway VMs just loaf along at this pace with just 2-3% CPU load, and heap well under 1G the whole time.
The client for the v7.7.8 gateway also loafs along while keeping pace with the data flow, showing all the timestamps and counter values changing at blistering speed. The project’s tag poll rate is 100ms to match the driver RPI. This video shows the v7.7.8 client with a diagnostic window overlaid.
I popped up the v7.9.1 client to watch the two client run together and was surprised to see the exact same project not keeping the display up to date. Still with a 100ms tag poll rate, but the client can barely update once per second. See this video.
A bit flummoxed, I pull up the client from the v7.8.4 gateway, and its plodding along at about the same speed as the v7.9.1 gateway. Pitiful. See this video.
Anyone know what might be involved here? All of the above, gateways and three clients, are all running simultaneously on my laptop with virtual network, so there’s no real network hardware making a bottleneck here, and it’s easy to see from the v7.7.8 client that all of the gateways are happily charging on. It’s only the newer clients that are choking.