HOLACONF - Cloud Forward 2015 Conference From Distributed to Complete Computing HAMZA. in collaboration SAHLI with

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LIRE Laboratory, Constantine II University-Abdelhamid Mehri

HOLACONF - Cloud Forward 2015 Conference From Distributed to Complete Computing

Pr. Faiza BELALA and Dr. Chafia BOUANAKA

HAMZA SAHLI

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1.  Introduc+on

2.  Bigraphical Reac+ve Systems (BRS)

3.  Modelling Cloud Systems and Their Elas+c Behavior 4.  Reachability Checking

5.  Conclusion

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What is Cloud Compu+ng?

(*): Na+onal Ins+tute of Standards and Technology (NIST)

Cloud Forward 2015 12/10/15

According to NIST (*) « Cloud compu*ng is a model for enabling ubiquitous, convenient, on-‐demand network access to a shared pool of configurable compu*ng resources that can be rapidly provisioned and released with minimal management effort or service provider interac*on. This cloud model is composed of five essen*al characteris*cs, three service models, and four deployment models »

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•  The emergence of the cloud has raised new issues and new security

concerns.

•  A DDoS a@ack, is an explicit a@empt to make a server, a service or a network unavailable to users by ﬂooding the target request queue with fake requests.

•  Cloud accessibility from everywhere exposes it to various types of web-‐ based a@acks suck as the DDoS (distributed denial of service) a@acks.

Cloud Forward 12/10/15

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« The degree to which a system is able to adapt to workload changes by

provisioning and deprovisioning resources in an autonomic manner »

Herbst and colleagues, 2013.

Cloud Forward 2015 12/10/15 1.  Horizontal scale; 2.  VerQcal scale; 3.  MigraQon.

•  According to the classiﬁcaQon of Galante and Bona, the elasQcity can be provided using three fundamental methods:

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•  The lack of a generic and exhausQve methodology for modeling and analyzing cloud-‐based systems and their elasQcity.

Cloud Forward 12/10/15

•  Formal methods a crucial step to reduce the modelling complexity and enhance the veriﬁcaQon of cloud-‐based systems and their elasQc behavior. Modeling and analyzing challenges:

Solu+on:

à An approach based on bigraphical reacQve systems (BRS) for modeling the structure and behavior aspects of cloud systems and Maude language for the veriﬁcaQon of elasQcity property.

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•  Graphical formalism for modelling, execuQng and analyzing

ubiquitous compuQng systems.

•  Meta-‐model which emphasizes both locality and connecQvity.

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12/10/15 Cloud Forward ₂₀₁₅

Formally a bigraph takes the form: 𝐺=(𝑉, 𝐸, 𝑐𝑡𝑟𝑙, 𝐺↑P , 𝐺↑L ) :𝐼→𝐽

§  V and E are respecQvely ﬁnite sets of nodes and edges

§  𝑐𝑡𝑟𝑙=𝑉→𝐾 is a control map.

§  𝐺↑P =(𝑉, 𝑐𝑡𝑟𝑙, 𝑝𝑟𝑛𝑡):𝑚→𝑛 is the place graph.

•  𝑝𝑟𝑛𝑡 :𝑚⨄↑▒𝑉 →𝑉 ⨄↑▒𝑛  is a parent map.

•  𝑚 is a ﬁnite ordinal number which represents sites.

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12/10/15 Cloud Forward

Formally a bigraph takes the form: 𝐺=(𝑉, 𝐸, 𝑐𝑡𝑟𝑙, 𝐺↑P , 𝐺↑L ) :𝐼→𝐽

§  𝐺↑L =(𝑉, 𝐸, 𝑐𝑡𝑟𝑙, 𝑙𝑖𝑛𝑘):𝑋→𝑌 is the link graph. •  𝑙𝑖𝑛𝑘 :𝑋⨄↑▒𝑃 →𝐸 ⨄↑▒𝑌  is the link map.

•  𝑋, Y , Y are respecQvely sets of are respecQvely sets of inner inner andand outer names outer names. .

•  𝑃 is a set of is a set of ports. ports.

§  𝐼= 〈𝑚,𝑋〉 represents the inner face. §  𝐽= 〈𝑛, 𝑌〉 represents the outer face.

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•  Bigraphical ReacQve Systems consist of a category of bigraphs and a

set of reacQon rules.

•  ReacQon rules deﬁne the dynamics of bigraphs (NesQng and Linking).

A reacQon rule (𝑅, 𝑅′, 𝜂) consists of a redex (𝑅:𝑚→𝐽) which may be

transformed to a reactum (𝑅↑′ :𝑚↑′ →𝐽) to rewrite the bigraph where 𝜂: 𝑚↑′ → 𝑚 is map is map of ordinals. of ordinals.

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•  Formal mapping based on correspondences between cloud system and BRS concepts.

12/10/15 Cloud Forward ₂₀₁₅

Cloud elements Bigraphical concepts Cloud system structure

Cloud system

Bigraph 𝐶𝑆 =( 𝑉↓𝐶𝑆  , 𝐸↓𝐶𝑆  ,

𝑐𝑡𝑟𝑙↓𝐶𝑆 ,𝐶𝑆↑𝑃 ,𝐶𝑆↑𝐿  )

Front-‐end, back-‐end Root: (0,1) Client, data center, load

balancer, server, container,

virtual machine, service Node: 𝑣∈𝑉↓𝐶𝑆  Node idenQty Control: 𝑘∈𝐾↓𝐶𝑆  

InteracQon Edge/Hyper edge: 𝑒↓𝑖 ∈𝐸↓𝐶𝑆  Abstract element Site: 𝑠↓𝑖 ∈𝑆↓𝐶𝑆 

Cloud system elas+c behavior

ElasQcity acQon ReacQon rule : C𝑆 →ℛ ┴  𝐶 𝑆↑′  /

ℛ=(𝑅,𝑅↑′ ,𝜂)

•  Each idenQﬁed cloud e l e m e n t h a s a precise semanQcs in the theory of BRS.

•  Cloud system elasQc behavior is formally d e ﬁ n e d u s i n g reacQon rules.

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12/10/15 Cloud Forward Front-‐End/Back-‐End Loaded Server Open Link Addi+onal VM Nodes

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12/10/15 Cloud Forward ₂₀₁₅

•  Each reacQon rule represent an elasQcity acQon which can be : triggered in response to workload changes, and applied in a speciﬁc cloud level (so_ware, pla`orm and infrastructure).

•  This work focus only on modelling horizontal elasQcity and migraQon methods.

•  Cloud-‐based systems elasQc behavior is expressed trough reacQon rules: C𝑆 →ℛ ┴ 𝐶𝑆↑′ / ℛ=(𝑅,𝑅↑′ ,𝜂).

•  AddiQonal reacQon rules are deﬁned to express other behavioral situaQons (e.g. service allocaQon).

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Cloud system BRS

Conﬁgura+on CS _Bigraph:𝐶𝑆 =(𝑉↓𝐶𝑆 ,𝐸↓𝐶𝑆 ,𝑐𝑡𝑟𝑙↓𝐶𝑆 ,𝐶𝑆↑𝑃 ,𝐶𝑆↑𝐿  )

Reconﬁgura+on from CS to CS’. _{Meta-‐ReacQon rule:} 𝐶𝑆 →ℛ ┴ 𝐶𝑆↑′ / ℛ=(𝑅,𝑅↑′ ,𝜂)

Infrastructure Level

Vm instance replica+on (horizontal scale)

𝑆𝐸.𝑉𝑀.(𝑆|𝑆↑′ |𝐿)⁠𝑑 → 𝑆𝐸.𝑉𝑀.(𝑆)⁠𝑉𝑀′.(𝑆′)|𝑑 

Vm instance consolida+on (horizontal scale)

𝑆𝐸.𝑉𝑀.(𝑆)⁠𝑉𝑀′.(𝑆′)|𝑑 →𝑆𝐸.𝑉𝑀.(𝑆|𝑆′)⁠𝑑 

Virtual machine migra+on

𝑆𝐸.(𝑉𝑀.(𝑑)|𝐿|𝑑′)|𝑆𝐸′.(𝑑′′)→ 𝑆𝐸.(𝑑↑′ )|𝑆𝐸′.(𝑉𝑀.(𝑑)|𝑑′′)

Plaaorm Level

Container instance replica+on (horizontal scale)

𝑆𝐸.𝐶𝑁.(𝑆|𝑆↑′ |𝐿)𝑑 ⁠ → 𝑆𝐸.𝐶𝑁.(𝑆)⁠𝐶𝑁′.(𝑆′)|𝑑 

Container instance consolida+on (horizontal scale)

𝑆𝐸.𝐶𝑁.(𝑆)⁠𝐶𝑁′.(𝑆′)|𝑑 →𝑆𝐸.𝐶𝑁.(𝑆|𝑆′)⁠𝑑 

Container redeployment (migra+on)

𝑆𝐸.(𝐶𝑁.(𝑑)|𝐿|𝑑′)|𝑆𝐸′.(𝑑′′)→ 𝑆𝐸.(𝑑↑′ )|𝑆𝐸′.(𝐶𝑁.(𝑑)|𝑑′′)

Service Level

Service instance replica+on (horizontal scale)

𝑆𝐸.(𝑉𝑀.𝑆⁠𝑑 |𝑑↑′ )→ 𝑆𝐸.(𝑉𝑀.𝑆⁠𝑆↑′ |𝑑 |𝑑↑′ )

Service instance consolida+on (horizontal scale)

𝑆𝐸.(𝑉𝑀.𝑆⁠𝑆↑′ |𝑑 |𝑑↑′ ) → 𝑆𝐸.(𝑉𝑀.𝑆⁠𝑑 |𝑑↑′ )

Service redeployment (migra+on)

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Virtual Machine Instance Replica+on

Loaded Virtual Machine New Vm Instance Load Shared 𝑺𝑬.𝑽𝑴.(𝑺|𝑺↑′ |𝑳)⁠𝒅 → 𝑺𝑬.𝑽𝑴.(𝑺)⁠𝑽𝑴′.(𝑺′)|𝒅 

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12/10/15 Cloud Forward ₂₀₁₅

•  Maude language was used as alternaQve to overcome these diﬀerent limits.

•  Maude is a high-‐level formal speciﬁcaQon language based on

equaQonal and rewriQng logics.

•  Tools built around BRS as BigMC (bigraphical model-‐checker) and DBtk are very limited and speciﬁc to some applicaQon domains.

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•  The syntax of this Maude speciﬁcaQon is fully inspired from the bigraph

term language. The speciﬁcaQon is composed of the following modules:

•  A projecQon from the BRS-‐based model of cloud systems to Maude

language.

1. BiCLOUD_SYNTAX : The model’s signature and semanQcs.

2. BiCLOUD_DYNAMIC: Behavioral aspects of the model through rewrite rules. 3. BiCLOUD_CHECK: states describing the elasQcity property (scale-‐up and scale-‐down states) speciﬁca+on + simula+on (execu+on) veriﬁca+on

•  The proposed Maude-‐based approach is generic enough and may be

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•  Maude’s search command and model-‐checking invariants technique are used in this work to verify the elasQcity property under ﬁnite reachability assumpQons.

•  The syntax of the search command conforms to the following general scheme: search ∶ <Term-‐1> <SearchArrow> <Term-‐2> such that <Condi+on> •  Verifying the elasQcity property consists of checking that the cloud system is

scaling up, when the workload rises and scaling down when it drops.

In our case that means checking that the states (scale-‐up and scale-‐down) deﬁned in the maude module BiCLOUD_CHECK are reachable from an iniQal state (<Term-‐1>) .

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12/10/15 Cloud Forward Reached States Ini+al State End of Search

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•  Further reﬁnements and extensions to our bigraphical model of systems

to include addiQonal elasQcity aspects as the verQcal elasQcity.

•  A formal modeling and veriﬁcaQon approach for cloud systems and their

elasQcity based on bigraphical reacQve systems (BRS) and maude language.

•  Apply our approach on large-‐scale cloud-‐based systems.

•  Verify other proprieQes related to elasQc cloud-‐based systems.

Contribu+on:

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