This is the counterpart to
MR gets tokens for all input, output and the default filesystem when a MR job is submitted.
The APIs in FileSystem make it challenging to avoid duplicate tokens when there are file systems that have embedded
Here is the original description that Daryn wrote:
The token cache currently tries to assume a filesystem's token service key. The assumption generally worked while there was a one to one mapping of filesystem to token. With the advent of multi-token filesystems like viewfs, the token cache will try to use a service key (ie. for viewfs) that will never exist (because it really gets the mounted fs tokens).