@Private @Evolving

Package org.apache.hadoop.hdfs.server.federation.resolver

The resolver package contains indepedent data resolvers used in HDFS federation. The data resolvers collect data from the cluster, including from the state store. The resolvers expose APIs used by HDFS federation to collect aggregated, cached data for use in Real-time request processing. The resolvers are perf-sensitive and are used in the flow of the RouterRpcServer request path.

The principal resolvers are:

• ActiveNamenodeResolver Real-time interface for locating the most recently active NN for a nameservice.
• FileSubclusterResolver Real-time interface for determining the NN and local file path for a given file/folder based on the global namespace path.

Interface Summary

Interface	Description
ActiveNamenodeResolver	Locates the most active NN for a given nameservice ID or blockpool ID.
FederationNamenodeContext	Interface for a discovered NN and its current server endpoints.
FileSubclusterResolver	Interface to map a file path in the global name space to a specific subcluster and path in an HDFS name space.
MountTableManager	Manage a mount table.
RouterGenericManager	Generic methods for managing Router.

Class Summary

Class	Description
FederationNamespaceInfo	Represents information about a single nameservice/namespace in a federated HDFS cluster.
MembershipNamenodeResolver	Implements a cached lookup of the most recently active namenode for a particular nameservice.
MountTableResolver	Mount table to map between global paths and remote locations.
MultipleDestinationMountTableResolver	Mount table resolver that supports multiple locations for each mount entry.
NamenodePriorityComparator	Compares NNs in the same namespace and prioritizes by their status.
NamenodeStatusReport	Status of the namenode.
PathLocation	A map of the properties and target destinations (name space + path) for a path in the global/federated name space.
RemoteLocation	A location in a remote namespace consisting of a nameservice ID and a HDFS path (destination).

Enum Summary

Enum	Description
FederationNamenodeServiceState	Namenode state in the federation.

Exception Summary

Exception	Description
RouterResolveException	Thrown by FileSubclusterResolver when a path can't be resolved.