ViewFs.getDelegationTokens returns a list of tokens for the associated namenodes. Credentials serializes these tokens using the service name for the actual namenodes. Effectively, tokens are not cached for viewfs (some more details in MR 3529). Affects any job which uses the TokenCache in tasks along with viewfs (some Pig jobs).
Talk to Jitendra about this, some options
1. Change Credentials.getAllTokens to return the key, instead of just a token list (associate the viewfs canonical name with a token in credentials)
2. Have viewfs issue a fake token.
Both of these would allow for a single viewfs configuration only.
3. An additional API in FileSystem - something like getDelegationTokens(String renewer, Credentials credentials) - which would check the credentials object before making token requests to the actual namenode.
4. An additional API in FileSystem - getCanonicalServiceNames - similar to getDelegationTokens, which would return service names for the actual namenodes. TokenCache/Credentials can work using this list.
5. have getDelegationTokens check the current UGI - and fetch tokens only if they don't exist.
Have a quick patch for 3, along with associated MR changes.