A Survey of Task Allocation and Load Balancing

A Survey of Task Allocation and Load Balancing in Distributed System

Part 1. Overview on Distributed Systems

the general characteristics of real distributed system

• lack of global control unit

  • reason:

    • large-scale

    • dynamic

    • hetergeneous

• distribution and sharing of resources

  • resource :

    • data

    • processor

    • computational capacity

    • disk storage

  • resource management

    • placement

    • provision

    • discovery

    • negotiation

• openness and unreliability of systems

• heterogeneous nodes

  • node in different organization has different property

  • compete for critical resource

• constraints of network structures

  • node communicate with

    • neighbouring nodes -- directly

    • non-neighbouring nodes -- be relayed by intermediate node

  • encounter the following situation

    • the tasks may be implemented by negotiation among nodes without a central control

    • the tasks are always implements by accessing required resources distributed in the networks

    • the tasks may be implemeted unreliably

    • the tasks performed by heterogenerous nodes may vary significantly and compete for critical resources

    • the performance of tasks may be influenced significantly by network structures

      • resource access performance

      • coordination performance

typical problems occur during the task allocation and load balancing

• control models

  • totally centralized control model -- difficult to implement

    • large , dynamic , lack global control unit

  • totally decentralized control model

    • require relative high computational costs from nodes, which place heavy loads on large systems and make the task allocation processes difficult to control effectively

• resource optimization

  • many models of task allocation and load balancing are implemented based on the optimization of accessibility of required resource

  • example : 2 situation

    • a node has plentiful resource, it has high resource accessbility

    • a node doesn't have plentiful resource, but it obtains enough resource from other node easily, it can also be allocated many tasks.

  • in a word, consider node's own resource and contextual resource

• reliablitily

• coordination among heterogenerous nodes

  • fact:hetergeneous nodes don't cooperate in making decisions while they execute tasks

  • questions:

    • 1. how to make noncooperative nodes coordinate

    • 1. how to incentivize nodes to contribute their resource

• considering network structures

  • communication and interaction of nodes are constrained by the network structures

objectives of task allocation in existing studies

• response time

  • 2 types

    • total response time

    • mean response time

• makespan

  • time of reansfer tasks to different nodes

  • waiting time of tasks at node

  • time for accessing resource

  • time for communicating resource

  • time for processing

• throughput

• raliability

  • 2 types

    • node-related reliability

      • source

      • computation

    • path-related reliability

      • communication path

Part 2. Control Model in Task Allocation and Load Balancing

Centralized Control Model

• central controller

  • know the status information of the entire system in real time

  • make all decisions.

  • may become the bottleneck

• Distributed Control Model

  • market-based approaches

    • game theory

      • a game theory pricing model

      • a game theory framework for obtaining user-optimal load balancing scheme

      • algorithm based on the strcuture of the Nash equilibrium

        • achieve of advantage of distributed structure

        • low complexity

        • optimality of allocation for each user

      • formulate the load balancing problem as a non-cooperative game among users

    • auctions

      • a decentralized market protocol for task allocation among nodes that contend for sacrce resource, where node trade tasks and resource at price determined by an auction protocol

      • a continuous double auction method for grid resource in which resources are considered as provider agents, and users are considered as consumer agents

      • consensus-based auction

      • a metaschedular based on the double auction mechanism

    • contract mechanisms

  • society-based approaches

    • strategy diffusion

      • denote:

        • the large scale of strategy penetrations of certain agents on other agents

      • negotiation between neighbouring nodes for tasks can be described as a diffusion process

      • advantage

        • each node only knows the information of neighbouring nodes and global optimal result can be achieved finally

    • coalition formation

      • a coalition is a alliance among individuals, in which individuals coopertae in joint action

      • a task allocation scheme via self-roganizing swarm coalitions for distributed mobile sensor network coverage, which uses the concepts of ant behavoir to self-regulate

      • community-aware task allocation model for social network systems where a node's coopertaion domain is constrained in a community and each node can negotiation only with its intracommunity member nodes

      • agent-based decentralized task allocation mechanism. An agent will be aotumatically dispatched to ask immediately after the task is randomly submitted to a node.

      • multiagent-based load balancing model where each agent has a credit value. The agent with low credit value is migrated to a ralatively lightly loaded workstation

    • group mechanisms

    • Mathhew effect

  • agent-based approaches

  • other approaches

Hybrid Control Model

• Future Research Directions

  • how to customize control model

  • how to coordinate the different control models of different subsystems

  • self-adaptation and evolution of control models for dynamic distributed systems

Part 3. Resource Optimization in Task Allocation And Load Balancing

taks allocation often means allocating tasks to resources

• Self-Owned Resource-Based Optimization

  • implemented based on nodes' self-owned resource statuses

• Contextual Resource-Based Optimization

  • implemented based on not only nodes' self-ownded resource statuses but alse their contextual resource statuses

  • approach

    • if a node's contextual nodes have richer experiences of executing tasks, the node may have higher access to the resources even if it seldom accessed the resources by itself

    • contextually-experienced nodes recived more new tasks than less contextually-experienced nodes

• future research

  • predict resource access

  • resource optimization scheme should adapt to dynamic change of resource distribution

Part 4. Reliability in Task Allocation And Load Balancing

Redundancy-Based Approaches

• redundancy of resources

• redundancy of tasks

Non-Redundancy-Based Approaches

• optimization mechanisms for reliability

• trust-or reputation-based approaches

  • trust-based approaches

  • reputation-based approaches

Part 5. Coordination Among Hetergeneous Nodes in Task Allocation And Load Balancing

game theory-based approaches

other approaches

Part 6. Considering Network Structures in Task Allocation And Load Balancing

• physical communication networks

• virtual interaction networks