Deadlock Detection in Distributed Systems

Dr. Davarpanah

Research: Kaywan ZayerReza Ramezani

Mohammad Khosravi

Deadlock

• Introduction• Strategies to handle deadlock– Ostrich algorithm (ignore it)– Detection (let occur, detect, recover)– Prevention (make it impossible to occur)– Avoidance (careful resource allocation)

Deadlock Detection

• Centralized– Single point of failure– bottleneck

• Distributed– Soojung Lee– Monjurul Alom et al– Farajzadeh et al

Introduction

• Process dependency– wait-for graph (WFG)

• Request model– AND– OR– p out-of q

• Communication model– Just message communication– Bounded delay, reliable protocol

Soojung Lee

• Dependency Model– Reduced wait-for graph (RWFG)– knot

• Request model– OR

• Blocked process can participate in deadlock detection algorithm

Message

• Probe– Distributed Spanning Tree (DST)– Path-string decoding– Unique id

• Reply– ACTIVE– REPORT

Example

(i) WFG (ii) DST

Example

(iii) RWFG after receive ACTIVE(iv) RWFG after receive REPORT (v) Final RWFG

Monjurul Alom et al

• Distributed Database System• Dependency model– Transaction wait-for graph (TWFG)

• Request model– AND

• Linear Transaction Structure (LTS)• Distributed Transaction Structure (DTS)

Algorithm Scheme

• LTS for each local site• DTS for global resource transaction communication• Priority Id for each transaction in each of the

sites• The local and global cycles• Abort of the victim transaction based on the

cycles

Example

TWFG

Example

LTS2 : {3->5, 5->6, 6->3} {7->10, 10->9, 9->7}{10->9, 9->11, 11->10}LTS3 :

Example

Example

DTS1 : {4->3, 3->3, 3->4, 4->4} DTS2 : {6->4, 4->8, 8->7, 7->6}

Detected deadlock, breaking it

Final TWFG

Farajzadeh et al

• History-based edge chasing– Probe message

• Request model– p out-of q

• Messages– Probe– Clean-up– Ok– Deny

Algorithm

• Receive probe– In memory and id = received id

• Prefix of received route-string– deadlock

• Otherwise– Save probe with smaller path-string and propagate received probe

• Deadlock– Initiator

• Clean-up and suicide

– Otherwise• Request permission for suicide

Comparison• First an third algorithm– Both use probe messages– Build WFG– Different in message number, delay, message size

and resolution schemeSujung lee farajzadeh

Number of message

2e <=e

Message size d+2 <=O(d)

delay O(dlogn) n

resolutaion yes Yes, 2 message

e : number of edge in WFG, n : number of node, d : diameter of WFG