Traffic Ops should auto-calculate the max origin connections per mid

[dneuman64]

I'm submitting a ...

• new feature / enhancement request

Traffic Control components affected ...

• Traffic Ops
• Traffic Portal

Current behavior:

Currently, if the max origin connections field is set in TO, it is only used to determine connections per server for DSs that do NOT use Mids.

New behavior:

If the Max Origin Connections field is set, Traffic Ops should automatically calculate the number of connections per Edge OR Mids for a DS. This should be based on the amount of REPORTED caches.

Minimal reproduction of the problem with instructions:

Anything else:

[dneuman64]

It looks like Traffic Portal might not make that field available for all DSs, so TP might need to be fixed as well.

[ocket8888]

Also, if it currently does only apply to Edge-tier cache servers, then the related documentation is wrong, as it specifies that the setting applies to Mid-tier cache servers.

[rob05c]

ORT should be calculating and applying it to Edges for direct DSes (HTTP_LIVE, DNS_LIVE) and to Mids for DSes that use the Mids: https://github.com/apache/trafficcontrol/blob/master/lib/go-atscfg/headerrewritemiddotconfig.go#L153

Unless there's a bug.

IMO it's better for ORT to do the calculation than TO, just because it's more canaryable.

[mitchell852]

ORT should be calculating and applying it to Edges for direct DSes (HTTP_LIVE, DNS_LIVE) and to Mids for DSes that use the Mids: https://github.com/apache/trafficcontrol/blob/master/lib/go-atscfg/headerrewritemiddotconfig.go#L153

yeah, i thought it did this as well. I originally created this feature in TP/TO and @rob05c moved it into ORT which i believe is the right place to do the calculations. Possibly a bug?

[rawlinp]

We also need to keep topologies in mind here -- the origin connections need to be calculated based upon the number of caches in the last (non-origin) tier of the DS's topology.