[YARN-19] 4-layer topology (with NodeGroup layer) implementation of Container Assignment and Task Scheduling (for YARN)

• Type: New Feature
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Assignee: Junping Du
• Reporter: Junping Du
• Created: 04/Jun/12 06:21
• Updated: 04/Jun/15 05:56

Description

There are several classes in YARN’s container assignment and task scheduling algorithms that related to data locality which were updated to give preference to running a container on the same nodegroup. This section summarized the changes in the patch that provides a new implementation to support a four-layer hierarchy.
When the ApplicationMaster makes a resource allocation request to the scheduler of ResourceManager, it will add the node group to the list of attributes in the ResourceRequest. The parameters of the resource request will change from <priority, (host, rack, *), memory, #containers> to <priority, (host, nodegroup, rack, *), memory, #containers>.
After receiving the ResoureRequest the RM scheduler will assign containers for requests in the sequence of data-local, nodegroup-local, rack-local and off-switch.Then, ApplicationMaster schedules tasks on allocated containers in sequence of data- local, nodegroup-local, rack-local and off-switch.
In terms of code changes made to YARN task scheduling, we updated the class ContainerRequestEvent so that applications can requests for containers can include anodegroup. In RM schedulers, FifoScheduler and CapacityScheduler were updated. For the FifoScheduler, the changes were in the method assignContainers. For the Capacity Scheduler the method assignContainersOnNode in the class of LeafQueue was updated. In both changes a new method, assignNodeGroupLocalContainers() was added in between the assignment data-local and rack-local.

Issue Links

• blocks: HADOOP-10512 Document usage of node-group layer topology
• depends upon: YARN-18 Configurable Hierarchical Topology for YARN
• depends upon: HDFS-3601 Implementation of ReplicaPlacementPolicyNodeGroup to support 4-layer network topology
• is part of: HADOOP-8468 Umbrella of enhancements to support different failure and locality topologies