OCHEI 2017 Architecting the development of cloud-hosted services

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Architecting the Deployment of
Cloud-hosted Services for
Guaranteeing Multitenancy Isolation
Laud Charles Ochei
A thesis submitted in partial fulfilment
of the requirements of
Robert Gordon University
for the degree of Doctor of Philosophy
May 2017
Abstract
Inrecentyears,softwaretoolsusedforGlobalSoftwareDevelopment(GSD)processes(e.g.,con-
tinuousintegration,versioncontrolandbugtracking)areincreasinglybeingdeployedinthecloud
to serve multiple users. Multitenancy is an important architectural property in cloud computing
in which a single instance of an application is used to serve multiple users. There are two key
challenges of implementing multitenancy: (i) ensuring isolation either between multiple tenants
accessing the service or components designed (or integrated) with the service; and (ii) resolving
trade-offsbetweenvaryingdegreesofisolationbetweentenantsorcomponents.
Theaimofthisthesisistoinvestigatehowtoarchitectthedeploymentofcloud-hostedservice
while guaranteeing the required degree of multitenancy isolation. Existing approaches for archi-
tectingthedeploymentofcloud-hostedservicestoservemultipleusershavepaidlittleattentionto
evaluatingtheeffectofthevaryingdegreesofmultitenancyisolationontherequiredperformance,
resource consumption and access privilege of tenants (or components). Approaches for isolating
tenants(orcomponents)areusuallyimplementedatlowerlayersofthecloudstackandoftenapply
totheentiresystemandnottoindividualtenants(orcomponents).
Thisthesisadoptsamultimethodresearchstrategytoprovidingasetofnovelapproachesfor
addressing these problems. Firstly, a taxonomy of deployment patterns and a general process,
CLIP (CLoud-based Identification process for deployment Patterns) was developed for guiding
architects in selecting applicable cloud deployment patterns (together with the supporting tech-
nologies) using the taxonomy for deploying services to the cloud. Secondly, an approach named
COMITRE (COmponent-based approach to Multitenancy Isolation Through request RE-routing)
wasdevelopedtogetherwithsupportingalgorithmsandthenappliedtothreecasestudiestoempir-
icallyevaluatethevaryingdegreesofisolationbetweentenantsenabledbymultitenancypatterns
for three different cloud-hosted GSD processes, namely-continuous integration, version control,
andbugtracking. Afterthat,asynthesisoffindingsfromthethreecasestudieswascarriedoutto
provideanexplanatoryframeworkandnewinsightsaboutvaryingdegreesofmultitenancyisola-
tion. Thirdly,amodel-baseddecisionsupportsystemtogetherwithfourvariantsofametaheuristic
solution was developed for solving the model to provide an optimal solution for deploying com-
ponentsofacloud-hostedapplicationwithguaranteesformultitenancyisolation.
Bycreatingandapplyingthetaxonomy,itwaslearntthatmostdeploymentpatternsarerelated
and can be implemented by combining with others, for example, in hybrid deployment scenarios
tointegratedataresidinginmultipleclouds. Ithasbeenarguedthatthesharedcomponentisbetter
for reducing resource consumption while the dedicated component is better in avoiding perfor-
mance interference. However, as the experimental results show, there are certain GSD processes
wherethatmightnotnecessarilybeso,forexample,inversioncontrol,whereadditionalcopiesof
the files are created in the repository, thus consuming more disk space. Over time, performance
beginstodegradeasmoretimeisspentsearchingacrossmanyfilesonthedisk. Extensiveperfor-
mance evaluation of the model-based decision support system showed that the optimal solutions
obtained had low variability and percent deviation, and were produced with low computational
effortwhencomparedtoagiventargetsolution.
Keywords: Cloud-hostedServices,CloudPattern,ApplicationComponent,GlobalSoftwareDe-
velopment(GSD)tools,Multitenancy,DegreeofIsolation,Metaheuristic,ContinuousIntegration,
Versioncontrol,Bugtracking.
Acknowledgments
My family has been very supportive. Thanks so much to Nkem, my darling wife, and our twin
boys-DavidandDaniel. IwouldalsoliketothankmyMum,Dad,AuntiesandUncles,Grandma,
in-laws,otherfamilymembersandfriends,fortheirsupportandprayers.
I would like to thank my supervisors, Julian Bass and Andrei Petrovski, especially for the
patience and understanding they showed me when I was struggling in the initial stages of the
research. I would like to sincerely thank Julian Bass for agreeing to be part of my supervisory
team despite leaving RGU in August 2015. I would like to thank Olivier for the comments I
received during the modelling and simulation phase of the research. Many thanks to the School
of Computing, IT staff: Colin Beagrie and Tommy Taylor for the technical support in setting up
and managing the private cloud used for the experiment. I would also like to thank the School
ofComputingforapprovingfundsformetoattendandpresentpapersatresearchconferencesin
Nice(France),Cambridge(USA)andLondon(England).
IalsowishtothankmynetworkoffriendsAnthonyEtuk,SadiqSani,Aminu,Amina,Mariam,
Mayowa and Blessing and Ikechukwu. Thanks so much for sharing your experiences with me;
that made the research process less stressful. Finally, I would like to thank Sylvester Ofogba,
StanleyOkosodo,GbengaGoker,RhibetnanYaktal,fortheirencouragement;andmembersofthe
FountainofLove(FOL),RCCG,Aberdeen,forbeingeverpresentwithloveandcheer.
Lastly,IamgratefultoGodAlmighty,forHisloveandcareinmylife.
ThisresearchwassponsoredbytheTertiaryEducationTrustFund(TETFUND)andtheUni-
versity of Port Harcourt (UNIPORT), Nigeria. The views and conclusions contained in this doc-
umentarethoseoftheauthor(s)andshouldnotbeinterpretedasrepresentingtheofficialpolicies
oftheNigerianorUKGovernments. TETFUND,UNIPORT,theNigerianandU.K.Governments
areauthorisedtoreproduceanddistributereprintsforGovernmentpurposesnotwithstandingany
copyrightnotation.
Declarations
IdeclarethatIamthesoleauthorofthisthesisandthatallverbatimextractscontainedinthethesis
have been identified as such and all sources of information have been specifically acknowledged
in the bibliography. Parts of the work presented in this thesis have appeared in the following
publications:
• L. C. Ochei, J. M. Bass, and A. Petrovski, A novel taxonomy of deployment patterns for
cloud-hosted applications: A case study of global software development (gsd) tools and
processes, International Journal On Advances in Software., vol. volume 8, numbers 3 and
4,pp. 420434,2015. (Chapter4)
• L. C. Ochei, J. M. Bass, and A. Petrovski, Evaluating degrees of multitenancy isolation:
A case study of cloud-hosted gsd tools, in 2015 International Conference on Cloud and
AutonomicComputing(ICCAC).IEEE,2015,pp. 101112. (Chapter5and6)
• L.C.Ochei,A.Petrovski,andJ.Bass,Evaluatingdegreesofisolationbetweentenantsen-
abledbymultitenancypatternsforcloud-hostedversioncontrolsystems(vcs),International
JournalofIntelligentComputingResearch,vol. 6,Issue3,pp. 601 612,2015. (Chapter5
and6)
• L. C. Ochei, A. Petrovski, and J. Bass, An approach for achieving the required degree of
multitenancy isolation for components of a cloud-hosted application, in 4th International
IBMCloudAcademyConference(ICACON2016),2016. (Chapter5and6)
• L. C. Ochei, J. Bass, and A. Petrovski, Implementing the required degree of multitenancy
isolation: A case study of cloud-hosted bug tracking system, in 13th IEEE International
ConferenceonServicesComputing(SCC2016). IEEE,2016.(Chapter5and6)
• L.C.Ochei,A.Petrovski,andJ.Bass,OptimizingtheDeploymentofCloud-hostedAppli-
cationComponentsforGuaranteeingMultitenancyIsolation,2016InternationalConference
onInformationSociety(i-Society2016). BestPaperAward. (Chapter7)
Contents
1 Introduction 1
1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 ProblemContext . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 ResearchMotivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.4 ResearchAimandObjectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.5 ContributionsoftheThesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.6 ThesisStructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2 LiteratureReview 15
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2 Cloud-hostedGSDProcessesandSupportingTools . . . . . . . . . . . . . . . . 15
2.2.1 CloudComputing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.2.2 GlobalSoftwareDevelopment . . . . . . . . . . . . . . . . . . . . . . . 17
2.2.3 GSDToolsandSupportingProcesses . . . . . . . . . . . . . . . . . . . 18
2.2.4 DeploymentofSoftwareToolstotheCloud . . . . . . . . . . . . . . . . 20
2.3 ArchitecturesforCloud-hostedApplications . . . . . . . . . . . . . . . . . . . . 21
2.3.1 ArchitecturalPatterns. . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.3.2 CloudDeploymentPatterns . . . . . . . . . . . . . . . . . . . . . . . . 22
2.4 TaxonomiesandClassificationsofCloudDeploymentPatterns . . . . . . . . . . 23
2.4.1 WhatisaTaxonomyanditsPurpose? . . . . . . . . . . . . . . . . . . . 23
2.4.2 Related Work on Taxonomies and Classifications of Cloud Deployment
Patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.5 ImplementingMultitenancyIsolationinaCloudComputingEnvironment . . . . 26
i
CONTENTS ii
2.5.1 MultitenancyIsolation . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.5.2 RelatedWorkonApproachesforImplementingMultitenancy . . . . . . 27
2.5.3 RelatedWorkonDegreesofMultitenancyIsolation . . . . . . . . . . . . 28
2.6 OptimizingComponentsDeploymentforGuaranteeingMultitenancyIsolation . . 30
2.6.1 ConflictingTrade-offsinMultitenancyIsolation . . . . . . . . . . . . . 30
2.6.2 RelatedWorkonOptimalDeploymentandAllocationofCloudResources 31
2.7 ConclusionsfromLiteratureReview . . . . . . . . . . . . . . . . . . . . . . . . 32
2.8 ChapterSummary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3 Methodology 37
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
3.2 TheMultimethodResearchApproach . . . . . . . . . . . . . . . . . . . . . . . 37
3.3 Phase1: ExploratoryStudy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.3.1 SelectionofGSDToolsandProcesses . . . . . . . . . . . . . . . . . . . 39
3.3.2 ExploringCloudDeploymentPatterns . . . . . . . . . . . . . . . . . . . 40
3.4 Phase2: CaseStudyandCaseStudySynthesis . . . . . . . . . . . . . . . . . . 40
3.4.1 CaseStudy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3.4.2 EvaluationoftheCaseStudy . . . . . . . . . . . . . . . . . . . . . . . . 42
3.4.3 SynthesizingthefindingsoftheCaseStudies . . . . . . . . . . . . . . . 50
3.4.4 DrawingConclusionsandDiscussingtheImplicationsoftheStudy . . . 50
3.5 Phase3: ModellingandSimulation . . . . . . . . . . . . . . . . . . . . . . . . . 51
3.5.1 DatasetandInstanceGeneration . . . . . . . . . . . . . . . . . . . . . . 51
3.5.2 EvaluationMetricandAnalysisforSimulation . . . . . . . . . . . . . . 55
3.5.3 Applicability of the Experiments and Frameworks in other Cloud Envi-
ronments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
3.6 MultimethodResearch: combiningexploratorystudy, casestudy, casestudysyn-
thesis,andsimulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
3.6.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
3.6.2 Howthedifferentmethodsfitintotheresearchprocess . . . . . . . . . . 60
3.7 ChapterSummary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
CONTENTS iii
4 TaxonomyofDeploymentPatternsforCloud-hostedServices 62
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
4.2 DevelopingaTaxonomyofCloudDeploymentPattterns . . . . . . . . . . . . . 63
4.2.1 ProcedureforDevelopingtheTaxonomy . . . . . . . . . . . . . . . . . 63
4.2.2 DescriptionoftheTaxonomy . . . . . . . . . . . . . . . . . . . . . . . . 66
4.2.3 ValidationoftheTaxonomy . . . . . . . . . . . . . . . . . . . . . . . . 67
4.3 GSDToolSelection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
4.3.1 ResearchSite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
4.3.2 DerivedDatasetofGSDTools . . . . . . . . . . . . . . . . . . . . . . . 69
4.4 ApplyingtheTaxonomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
4.4.1 PositioningGSDToolsontheTaxonomy . . . . . . . . . . . . . . . . . 70
4.4.2 HowtoIdentifyApplicableDeploymentPatternsusingtheTaxonomy . . 71
4.4.3 CaseStudy: SelectingPatternsforAutomatedBuildVerificationProcess 73
4.5 Findings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
4.6 RecommendationsforusingtheTaxonomy . . . . . . . . . . . . . . . . . . . . 79
4.7 ChapterSummary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5 CaseStudiesofDegreesofMultitenancyIsolationusingCOMITREApproach 84
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
5.2 COMITRE:AnApproachforImplementingMultitenancyIsolation . . . . . . . 85
5.2.1 ArchitectureandProcedureforImplementation . . . . . . . . . . . . . . 85
5.2.2 AlgorithmsforSupportingCOMITRE . . . . . . . . . . . . . . . . . . . 87
5.2.3 ValidatingtheImplementationofMultitenancyIsolation . . . . . . . . . 90
5.2.4 ScenariosforIllustratingMultitenancyIsolation . . . . . . . . . . . . . 91
5.3 CaseStudy1-ContinuousIntegration . . . . . . . . . . . . . . . . . . . . . . . 93
5.3.1 ImplementingMultitenancyIsolationinHudson . . . . . . . . . . . . . 93
5.3.2 ExperimentalProcedureforCasestudy1 . . . . . . . . . . . . . . . . . 93
5.3.3 ResultsforCaseStudy1 . . . . . . . . . . . . . . . . . . . . . . . . . . 94
5.4 CaseStudy2-VersionControl . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
5.4.1 ImplementingMultitenancyIsolationinFileSystemSCMPlugin . . . . 98
5.4.2 ExperimentalProcedureforCaseStudy2 . . . . . . . . . . . . . . . . . 98
CONTENTS iv
5.4.3 ResultsforCaseStudy2 . . . . . . . . . . . . . . . . . . . . . . . . . . 100
5.5 CaseStudy3-BugTrackingwithBugzilla . . . . . . . . . . . . . . . . . . . . 101
5.5.1 ImplementingMultitenancyIsolationinBugzilla . . . . . . . . . . . . . 101
5.5.2 ExperimentalProcedureforCaseStudy3 . . . . . . . . . . . . . . . . . 103
5.5.3 ResultsforCaseStudy3 . . . . . . . . . . . . . . . . . . . . . . . . . . 104
5.6 ChapterSummary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
6 DegreesofMultitenancyIsolation: SynthesisofthreeCasestudies 108
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
6.2 SynthesisofCaseStudiesFindings . . . . . . . . . . . . . . . . . . . . . . . . . 109
6.2.1 Cross-caseAnalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
6.2.2 NarrativeSynthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
6.3 ExplanatoryFrameworkforDegreesofMultitenancyIsolation . . . . . . . . . . 118
6.3.1 MappingofMultitenancyIsolationtoGSDProcessesandResources. . . 119
6.3.2 ExploringTrade-offsforAchievingMultitenancyIsolation . . . . . . . . 121
6.4 ValidityoftheCaseStudySynthesis . . . . . . . . . . . . . . . . . . . . . . . . 124
6.5 ChapterSummary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
7 OptimalDeploymentofComponentsforGuaranteeingMultitenancyIsolation 127
7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
7.2 ProblemFormalizationandNotation . . . . . . . . . . . . . . . . . . . . . . . . 128
7.2.1 SystemModelandDescriptionoftheProblem . . . . . . . . . . . . . . 128
7.2.2 SystemNotationsandAssumptions . . . . . . . . . . . . . . . . . . . . 129
7.2.3 MappingtheProblemtoaMultichoiceMultidimensionalKnapsackprob-
lem(MMKP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
7.3 OpenMulticlassQueuingNetworkModel . . . . . . . . . . . . . . . . . . . . . 134
7.4 MetaheuristicSearch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
7.5 DecisionSupportSystemforOptimalDeploymentofComponents . . . . . . . . 140
7.5.1 ArchitectureoftheDecisionSupportSystem . . . . . . . . . . . . . . . 140
7.5.2 OptimalDep: AnalgorithmforOptimalDeploymentofComponents . . . 142
7.6 EvaluationandResults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
7.6.1 ExperimentalSetupandProcedure . . . . . . . . . . . . . . . . . . . . . 145
CONTENTS v
7.6.2 Comparison of Solutions obtained from optimalDep Algorithm with the
OptimalSolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
7.6.3 Comparison of Solutions obtained from optimalDep algorithm with the
TargetSolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
7.6.4 StatisticalAnalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
7.7 ChapterSummary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
8 Discussion 160
8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
8.2 DiscussionofFindings: Exploratory,CaseStudies,SynthesisandModelling . . . 160
8.2.1 DiscussiononFindingsfromExploratoryStudyonDeploymentPatterns 160
8.2.2 DiscussionofFindingsfromCaseStudiesandCaseStudySynthesis . . . 163
8.2.3 DiscussionofFindingsfromModellingandSimulation . . . . . . . . . . 165
8.3 ChallengesandRecommendations . . . . . . . . . . . . . . . . . . . . . . . . . 168
8.3.1 TypeandLocationoftheapplicationcomponentorprocesstobeshared . 168
8.3.2 CustomizabilityoftheGSDtoolandsupportingprocess . . . . . . . . . 168
8.3.3 OptimizationofCloudResourceduetochangingWorkload . . . . . . . 169
8.3.4 HybridCloudDeploymentConditions . . . . . . . . . . . . . . . . . . . 170
8.3.5 TaggingComponentswiththeRequiredDegreeofIsolation . . . . . . . 171
8.3.6 ErrorMessagesandSecurityChallengesduringImplementation . . . . . 171
8.4 PracticalApplications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
8.5 ChapterSummary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
9 Conclusion 176
9.1 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
9.2 ResearchContributionsRevisited . . . . . . . . . . . . . . . . . . . . . . . . . . 177
9.3 ResearchScopeandLimitations . . . . . . . . . . . . . . . . . . . . . . . . . . 181
9.4 ReflectiononthePhD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
9.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
9.6 FutureWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
9.6.1 MultitenancyIsolationProblem: ExploringotherModelsandMetaheuristics188
9.6.2 PredictingQoSofComponentsbasedonRequiredDegreeofIsolation . . 189