high-entropy abfs/https proxy passwords don't make it through to yarn/mr worker processes

Fun one. ABFS proxy settings come through sysprops not hadoop conf options, so have to bse set in one of the various .java.opts config options -for am and workers.

Except with all the layers in the way, there are some corner cases of char which don't make it through. And the default solution "don't do that" comes up against central IT policies of "no can do"

Fix: work out what the brittle chars are escape so that launcher doesn't get the clever idea to join in.