云计算-服务迁移service-migration总结.docx

1.introduction云服务迁移是云计算实现中的一个概念，它确保了个体或组织的数据，或其它商业元素，能轻松地在不同的云供应商之间，或在一个私有云设施内部，转移或迁移，且不用克服实现、整合、兼容性及互操作性问题。通过服务迁移，应用，基础设施，或者任意云主持的应用、服务都能避免被锁定在一个运营商的情况。服务迁移也定义了应用能部署在其它云供应商或被私有云架构支持的过程及框架。服务迁移的整个过程由几个不同进程和技术组成，它们依赖于被迁移的应用或服务的复杂性。服务迁移也包括了通过在开放式标准和框架上设计、开发云基础架构，而进行的最佳实践的开发。服务前移是非常复杂的，因为大多数云服务供应商使用了专利技术，为了把数据从一个供应商的存储中转移到另一个，有时必须首先把数据移回用户自己的服务器上，然后再从这里转移到新的供应商地点。甚至这样时，由于需要格式的变换来确认数据也可能需要被重定格式，Even then, the data may need to be reformatted because of formatting changes made to conform to the first service providers system.Such a situation may lead to vendor lock-in a situation in which a product or service vendor has made it so difficult or expensive to transition to a competitors offering that customers are effectively “locked in.”2. Services Migration in Clouds2.1架构The servicemigration concept extends the notion of a service-orientedarchitecture.Web service has been the major standard for realizingSOA. Web services have good encapsulationand strong integration capabilities. Web services dynamicdistribution. Service providers and service requesters may bedistributed in different geographic locations. There are twoways to complete the request issued by the service requester.One is the data migration. The requester transfers data to aservice provider to have it analyzed. After that, the providerreturns the result back to the requester. The other way is theweb service migration. The requester desires to acquire aservice comes to his system to analyze the data. After thedata is processed, the service is moved from the requesterssystem. For a large amount of data, such as a large set ofgigabytes to terabytes, rendered across the wide area networkcan be costly, it may increase the communication latencysignificantly.Due to the reason above, many researches work on theweb service migration are interested in minimizing thecommunication cost. In cloud environment,hardwareresources and their management utilities are all provided asservices. A large number of services deployed in differentnetwork domains. So it can directly select the nearestservers to migrate the services. The term nearest coversessential factors of service quality, including networkbandwidth, network delay, server capacity, service type,connecting fee, etc.A new infrastructure to support themigration of web services in cloud is presented.The proposed infrastructure includes five components: Load&Proximity Analyzer (LPA), Services DependencyAnalyzer (SDA), Publish/Select Manager (PSM), ServiceMigration Manager (SMM), and Service Migration DecisionManager (SMDM).In current web infrastructure, theinteractions among all components are soap messages basedon httpihttps. A host can be a web service provider, a webservice requester, or even a web service proxy.1) 负载&邻近分析仪收集所有主机的cpu负载信息和主机与其邻居间的邻近信息，并更新维护。The LPA runs periodically to collect all hosts cpu loadinformation and the proximity information between the hostand its neighbors. When the network topology changes, itwill result in proximity change. We use the round trip timepackets and the number of hops they had traveled to reflectthe proximitys change. We also may use overage queuingdelay to reflect the cpus load information.2) 服务依赖分析仪管理服务器之间的呼叫依赖性，获取相关服务的配置参数和它们的依赖性，分析来确保所选服务的先前服务被加入到正确的PSM中。The SDA is used to manage the calling dependencyamong web services. Its function including capturing theconfiguration parameters of interrelated services and theirdependencies, analyzing the integrity to make sure that theantecedent services of the selected service are added to thecorrect PSM, avoiding incorrect cyclic dependencies ofsystem services, and generating proper configuration settingsequence.3) 发布/选择管理如果一个主机提供了特定的服务或接收了从其他主机迁移来的服务，它会向PSM发送注册请求。If a host provides a specific web service or receives aweb service which migrated from another host, it will sendthe registration request to the PSM. So there may have manyentries for the same web service. When a requester sendsweb service looking request to the PSM, it should decidewhich entry is the best for the requestor based on therequestors location, the information from the LPA, and thesecurity factors.4) 服务迁移决策管理收集分析从LPA何SDA来的必要数据，作出服务迁移的决定。考虑网络带宽，服务有效期，服务器容量，服务访问频率，可转移性等。The SMDM is responsible for collecting and analyzingthe essential data from LPA and SDA to make the decisionon service migration. Factors should be taken into accountare network bandwidth, service valid period, server capacity,service access frequency, and transferability, etc.5) 服务迁移管理在SMDM决定何时并向何处迁移服务后，SMM收集并打包服务的状态信息，把它们转移到目的主机，并在目的主机上重建执行服务的环境。After the SMDM decides when and where to migrate theweb service, the SMMcollects and packs the states ofservices, transfers them to the destination host, andreconstructs the executing environment on the target host.2.2服务迁移决策管理机制Before SMDM make migration decision, it should takethree aspects into account: whether a web service ismigratable, when to migrate a web service, and where tomigrate a web service.1）In cloud environment, web services not only meansoftware sources, but also include the hardware sources, thedevelopment platforms, the databases, etc. These sources arenot all suitable for migration. For example, during a host isexecuting a web service, it need to access data from adatabase which residents on a remote server. At this time, themigration cost to migrate the database to the host may be toohigh. Even the migration cost is acceptable, the conditions toset up the database may not meet for this host. So we canconsider that the migration of a database is unacceptable.Similarly, it is not feasible to migrate a hardware indistributed area. It denotes these kinds of sources areunmigratable. We can label a web service is migratable orunmigratable when it published. The SMDM may not sendmigration command to the SMM if a web service isunmigratable.2）提出负载门槛When to migrate a web service is an important factor forSMDM to make migration decision. One of the innovationsof this paper is that we propose a schema to determine themigration time. We predefine a overload threshold inSMDM. When the LPA collected the performance data fromall the hosts periodically, SMDM compares the data with theoverload threshold and makes migration decision accordingto the comparison results. For example, we may predefinethe migration condition is cpus use-ratio more than 80%.Once the data collected from LPA shows a providers usagerate of cpu is over the threshold, it means the serviceresidents on this provider should be migrated.3）After decided when to migrate, the next step for SMDMis to determine where the appropriate destination server toaccommodate the web service is migrated from the provider.When a provider publish a web service, it also providesconstraints that should be met to execute the web service(such as the required operation system, the minimal memoryrequirement etc) and the priority information among theseconditions. So there may have some candidate hosts in cloudcan provide the appropriate environment to accommodate theweb services. We should choose one among them. Thedecision is based on the conditions and the priorityinformation that the candidate can provide.4）Besides the consideration of constraints and the priorityinformation, the migration cost is also should be taken intoconsideration. When a client issues a web service request toa provider, the SDA constructs the web service call tree, theLPA collect round trip time between hosts and the averagequeuing delay. All these information are sent to the SMDM.SMDM computes the migration cost based on a cost modeland find the best host which yield lowest cost as a target host.3.Agent-based Service Migration Framework in Hybrid CloudFigure 1 shows the architecture of the proposedsystem, which involves a federated broker and the hybridenvironment. Since the public cloud is charged in pay-perusescheme, in general, it should provide dynamic provisionof resources involving the computing platform and requiredstorage. In other words, the proposed system can start newcomputing cluster from public cloud for new jobsdynamically while the loading of private cloud is overrun.Such capability is provided by most virtualization tools ofvirtual machine, such as XEN, Microsofts Hyper-V andKVM. The tools provide Application Programming Interfaceto manage the resource of virtual machine. In addition,private cloud and public cloud can be connected via virtualprivate network (VPN) or public network if do not considerthe security issue between private cloud and public cloud.3.1联盟代理Federated Broker layer is the second tier in thearchitecture. It is responsible for monitoring system resourceand all behaviors of resource, reconfiguring system scale,and migrating services and balancing the load betweenclouds. The layer consists of three agents and tworepositories; there are System Monitoring Agent,Reconfiguration Decision Agent, Service Migration Agent,Profiling Database, and System/Service InformationDatabase, respectively._ System Monitoring Agent (SyMA): The agent isresponsible for collecting the loading andremaindering resource related information of allnodes in the hybrid cloud. It will activelycommunicate with the Cluster Admin Agent (CAA)resided in each cluster periodically to get theinformation or passively receive the heartbeatmessage that contains the information from CAA.The information involving in the heartbeat are asfollows: 1) clusters name, 2) clusters loadinformation, 3) jobs etc. Upon receiving a heartbeatmessage, the SyMAwill log the information toProfiling Database and System/Server InformationDatabase._ Reconfiguration Decision Agent (RDA): The RDAis used to reconfigure and adjust the cloudenvironment after the reconfiguration policy isfitted. The RDA can retrieve current clusters statusand loading information in the cluster to decide toadjust the scale of public cloud or not. If the SyMAis noticed the private cloud is overloading, he willcontacts the RDA to initiate the reconfigurationprocess to balance the loading between private andpublic cloud. Also, the SyMAwill notify the RDAscale the public cloud down if the private cloud isunder loading during a time period._ Service Migration Agent (SeMA): It is responsiblefor managing and initiating the service migrationbetween private and public cloud. If RDA informsit that the public cloud is scaled up and send amessage to migrate a job to public cloud, the SeMAwill initiate the service migration process accordingto the policy of service migration. The policy andalgorithm will be depicted next section._ Profiling Database: The database is to store theprofile of public cloud including the resourceinformation the public cloud has, such as thenumber of VM, the size of memory and storage,the bandwidth of link to public cloud, and theusage of these resources, which can be used to helpfor making decision of scaling._ System/Service Repository: The repository keepsthe system and service related information, such asthe location of private and public cloud, theinformation of services run in the hybrid cloud, andso on.3.2云内的代理Except for the components in the federated layermentioned above, there are two agents will be developedinto both private and public cloud platform. They areCluster Admin Agent and Job Agent._ Cluster Admin Agent (CAA): The CAA is the maincomponent on the cluster, which can manage thewhole cluster and negotiate the actions with agents infederated layer. He also periodically collects clustersinformation, and sends them to SyMAthat isembedded within the heartbeat message. Besides, italso manages and guide the running of Job Agents runin the cluster._ Job Agent (JA): In order to deliver a service to othercloud, a service will be encapsulated into a JA beforemigrating to other cloud. A JA has all the informationa service needed, includes services execution file,services input data, the location to be migrated, andso on.Code mobility can be divided into two categories 5:strong mobility and weak mobility. The strong mobility ischaracterized as if it allows executin