> My Hive job is taking long time, what might be the possible problems?, what are all thing i need to look into?
Start with the client/HS2 log to identify what phase of the query is it slow during (and also if a job is slow, or if a local task is). Subsequently, check up counters and skew probabilities if its a straggling task slowing the wider job. These are just some ideas.
> Where default reducer run?
What is a 'default reducer'? Reducers are scheduled randomly across the cluster, as they have no real local data dependency. There's no 'default' location for them if that's what you mean to ask.
> For particular user I want to revoke web server access , how I can achieve this
Two-step process: Enable authentication on web consoles, and then use the ACL configs for Web UIs to only allow specific users.
> Can capacity and fair scheduler in same cluster possible, how? (for user1-Fair, for User2-Cpacity)
No - The RM does not support running multiple scheduler implementations within the same runtime.