At Comcast, we have been seeing a pattern of the same cache group being
overloaded nightly as traffic increases on the CDN. The cause was determined to
be a default location that the geolocation provider MaxMind returns for client
IPs that it does not have additional data for. For the US, MaxMind returns a
geolocation with the coordinates: 37.751,-97.822; this is a substantial amount
of traffic that is all directed to the nearest cache group.
The fix I have introduced is a new profile parameter for CRConfig.json named
'maxmind.default.override' in the format: '<countryCode>;<lat>,<long>'. When
MaxMind returns a default location, the code checks for a parameter entry with
the same country code. If an entry exists, the default location will be
overwritten with the coordinates of the parameter. This allows users to
determine where this traffic should be sent rather than using the cache group
closest to the MaxMind default location. The new parameter supports multiple
entries so that there can be override coordinates for more than one country.
Here is the PR: https://github.com/apache/incubator-trafficcontrol/pull/1866