Hello,
We have approx. 250k OPC tags from our PLC to ignition, which are spread over 7 OPC servers connection on the gateway. To add, the 250k tags are reasonably/evenly spread over approx. 300 tag groups from the designer onto these 7 OPC servers on the gateway.
However, every time when we download to the PLC and initialize Ignition, there is issue with OPC tags subscription to some of the random tag groups – logs as below. And it’s not always the same tag groups having this issue every time.
'Failed to create 199 items on subscription 'tag-group-tags_status9-leased': requestId=670 timed out after 60000ms'
It seems somehow ignition is incapable of subscribing to all the 250k OPC tags, not that we think 250k tags is that large amount for the 16 core & 38g ram gateway to handle. Maybe we are missing some settings somewhere?
Any idea what is causing this issue and how to solve it? Thank you.
Based on those log entries, I'd say your OPC servers are overloaded, not Ignition. What kind of PLC is this?
Hi Phil, it's Beckhoff 6032 which has its own OPCUA server that connect to ignition
So, you're probably stuck. Does Beckhoff offer more powerful hardware you can swap to? (All indications are that you've simply overloaded your PLC.)
Siemens plcs have a limit of around 2k tag subscriptions via opc-ua. I've never used beckhoff plcs, but are you sure they can handle 250k tags? Allen Bradley EIP practical limit is around 20-30k when you start seeing it fail to cope, depending on processor of course and on the tags you're reading. I'd say it could go higher if you built for efficiency
Thank you @pturmel @nminchin I checked with Beckhoff, and they commented that the PLC is capable of handling more than 250k opc tags. In the meantime, we are looking for options to optimize the PLC program and consulting with Inductive automation. I will let you know if any progress. Thank you!
I don’t think it helps that you have 7 OPC connections to the same server. Now, when connecting and reconnecting, 7 sets of subscriptions and items are being created concurrently instead of 1 at a time, which is obviously loading up the server and causing it to respond slowly.
It was configured this way because we were informed that Ignition is very linear, and we were under the impression that it's better to parallelize multiple connections to spread the load rather than having 1 concentrated connection. Hmmm, is this not the case?
It seems your server can’t handle the spread. Many of the OPC operations are linear/ serial by default for exactly this reason.
