For a Regional Delivery Service, MaxOriginConnections should only be divided among Servers within a single Cache Group

[zrhoffman]

This Feature Request affects these Traffic Control components:

• Traffic Control Cache Config (t3c, formerly ORT)
• Traffic Ops - Delivery Service Regional field: Optionally make Max Origin Connections per Cache Group #7111)
• Traffic Portal - Delivery Service Regional field: Optionally make Max Origin Connections per Cache Group #7111

Description

The MaxOriginConnections property of a Delivery Service determines how many connections to the origin can be made, across all caches in child Cache Groups of the Origin Cache Groups. The max origin connections per cache is computed as that MaxOriginConnections value divided by the number of caches in child Cache Group of the Origin Cache Group:

trafficcontrol/lib/go-atscfg/headerrewritedotconfig.go

Line 553 in 8362b86

maxOriginConnectionsPerServer := int(math.Round(float64(*ds.MaxOriginConnections) / float64(numLastTierServers)))

However, if a Delivery Service is only intended to be used in a specific Region, despite that Delivery Service having Cache Groups outside of that region, the computed maxOriginConnectionsPerServer value is lowered when more caches exist outside of that region, which is undesirable. In the case of a Regional Delivery Service, the maxOriginConnectionsPerServer should only divide MaxOriginConnections among caches within a given cache's own Cache Group.