Elasticity : Advanced Cloud Computing. Garth Gibson Greg Ganger Majd Sakr. Feb 6, Adv. Cloud Computing 1

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Elasticity 15-719: Advanced Clud Cmputing Garth Gibsn

1 Elasticity : Advanced Clud Cmputing Garth Gibsn Greg Ganger Majd Sakr Feb 6, Adv. Clud Cmputing 1

2 Advanced Clud Cmputing Elasticity Readings Req d Ref 1: Dynamically Scaling Applicatins in the Clud. Luis M. Vaquer, Luis Rder- Merin, and Rajkumar Buyya. ACM SIGCOMM Cmputer Cmmunicatins Review (CCR), v 41, n 1, Opt Ref 2: Jckey: guaranteed jb latency in data parallel clusters. Andrew D. Fergusn, Peter Bdik, Srikanth Kandula, Eric Butin, and Rdrig Fnseca. 7th ACM Eurpean cnf. n Cmputer Systems (EurSys '12), Opt Ref 3: Split/Merge: System Supprt fr Elastic Executin in Virtual Middlebxes. Shriram Rajagpalan, Dan Williams, Hani Jamjm, Andrew Warfield. 10th USENIX Symp. n Netwrked Systems Design and Implementatin (NSDI 13), Opt Ref 4: ElasTraS: An elastic, scalable, and self-managing transactinal database fr the clud. Sudipt Das, Divyakant Agrawal, Amr El Abbadi. ACM Trans. Database Syst. 38, 1, Article 5, Feb 6, Adv. Clud Cmputing 2

Web Servers The killer app Online retail service Mst cycles spent n web page rendering Custmers use http t brwser inventry, viewing pictures, lists, technical specs, price cmparisns befre requesting

3 Web Servers The killer app Online retail service Mst cycles spent n web page rendering Custmers use http t brwser inventry, viewing pictures, lists, technical specs, price cmparisns befre requesting a prduct be purchased and shipped t them Number f machines needed fluctuates with custmer interest, changing with inventry and marketing want t pay nly fr need Feb 6, Adv. Clud Cmputing 3

4 Basic service parallelizatin: Lad Balancer Incming stream f independent user requests brken int multiple separate streams, ne per allcated machine Lad balancer is nt necessarily elastic AWS charges fr CludWatch t mnitr yur EC2 instances AutScaling f the EC2 instances and recnfiguring f AWS Elastic Lad Balancer at n add l charge dcs.aws.amazn.cm/elasticladbalancing/latest/ DevelperGuide/SvcIntr_arch_wrkflw.html Feb 6, Adv. Clud Cmputing 4

5 Lad Balancing Mechanism DNS lad balancing ut f band, can distribute arbitrary bandwidth (nt limited by bandwidth f a ruter) Tells client a binding f a name t an IP (list), which makes dynamic changing f the binding hard, r at least up t the client Ruter balancing f cnnectin TCP r SSL bth start a cnnectin, flw data, then clse the cnnectin A ruter n the path can make a decisin fr the entire life f the cnnectin fr sme applicatins this might be lng, making dynamic balance hard Ruter balancing f requests embedded in a cnnectin If ruter understands prtcl embedded in cnnectin flw, it can make ruting decisins fr specific requests Mst dynamic apprach, but requires the mst prcessing in the ruter HTTP/HTTPS are the typical prtcls that are recgnized by lad balancers Feb 6, Adv. Clud Cmputing 5

6 Hw is elasticity prvided t web servers? Abstractly, an elasticity cntrller mnitrs allcated machines When verladed, add lad capability When under used, delete lad capability Adding/deleting dne by clud framewrk Feb 6, Adv. Clud Cmputing 6

7 Elasticity: Scale-ut r Scale-up? Hrizntal scaling (Scale-ut) Adding mre identically resurced instances Mst use f elasticity is dne this way Vertical scaling (Scale-up) Resizing the resurces allcated t an existing instance Des yur (IaaS) OS accept and utilize mre resurces n the fly? Mre netwrk bandwidth is prbably easy Mre memry is harder but pssible (eg. VM ballning) Changing cres is even harder PaaS cntainers might hide resurce representatin Eg. culd prvide mre MapReduce slts in same machine Feb 6, Adv. Clud Cmputing 7

8 Elasticity Cntrller Capability User takes mnitring ffered, defines rules fr when t take actins (mdels the applicatin) Mnitring Mnitr resurce usage at specified instances, threshld individually r in ttal Mnitr request sequence, lking fr patterns t recnfigure fr predicted lad Triggering Trigger n simple cnditins, threshlds, n mnitred instances, request stream Trigger n schedule (simple predictin) Trigger n cmplex frmula f many mnitred instances (a mdel f verall service quality) Actins: Launch single instances, r identical instances, r mdify existing instances Execute sequence f launches r mdificatins accrding t a dependency graph r wrkflw Execute prgrams that implement a mre abstract actin (launch and cnfigure multi-tier service) If a system is cmpsed f a scalable set f prcesses feeding/interacting with anther scalable set f prcesses implementing a very different functin, are they mnitred and scaled independently r is their elasticity inherently understd by ne elasticity cntrller? Hw gd are yur mdels fr hw yu applicatin actually depends n wrklad and resurces? Feb 6, Adv. Clud Cmputing 8

9 Tw tier services Mst cycles in web servers, but want t take rders t Originally rder taking wasn t even in clud Just send message Nw frntends (web) & backends (database) Elasticity is certainly pssible in IaaS but database scaling is nt simple replicatin f identical web server, s user scripts cmplex Feb 6, Adv. Clud Cmputing 9

10 Tw tier web server scaling Ahhah, PaaS where P == Web Service E.g. Ggle s AppEngine prvides a WSGI/CGI web server framewrk Built-in elastic lad balancing and scheduled actins fr cntainers Mst invked servers have t cmplete in less than 60 secnds Built in persistent key-value stre (datastre) & nn-persistent memcache fr simple database tier Users can instantiate Backends: bigger, lng running, billed differently Nt autscaled, but user cde can request (actuate) hrizntal scaling Used fr running traditinal database services, whse scaling is still hard Feb 6, Adv. Clud Cmputing 10

11 What abut a scalable relatinal database? Nt a feature f traditinal database, where users wned machines With a few pssibly imprtant restrictins, pretty easy (e.g. ElasTraS) Separate data at rest frm nging r recent access & mutatin Data at rest is stred in (nn-elastic) distributed pay-fr-use strage (HDFS) Recent access & mutatin servers are elastic (called Owning Transactin Managers) Database can be partitined but all transactins restricted t ne partitin Distributed transactins usually blck n lcks and bttleneck perfrmance scaling Elastic cntrller is als fault-tlerance manager Servers can shutdwn (flush t strage) r start up when cntrller re-assigns partitins Fr the cntrller itself, reliability prvided by replicatin (Zkeeper) Feb 6, Adv. Clud Cmputing 11

12 ElasTraS architecture scales OTM machines Feb 6, Adv. Clud Cmputing 12

Primary restrictin: limitatins n transactins Eliminate distributed transactins by rule each transactin can tuch nly data frm ne partitin But want dynamic repartitining S establish a lt f

13 Primary restrictin: limitatins n transactins Eliminate distributed transactins by rule each transactin can tuch nly data frm ne partitin But want dynamic repartitining S establish a lt f mini-partitins allwing each OTM t manage many ElasTraS data mdel expresses this as the tree rted at each rw f the primary table All transactins restricted t the tree beneath ne rw in the rt table Feb 6, Adv. Clud Cmputing 13

14 Migrating OTMs with minimal pause First, push cmpleted wrk t shared strage t reduce OTM state Next, fuzzy migrate f OTM state between servers Finally, stp prcessing requests fr final part f migratin Feb 6, Adv. Clud Cmputing 14

15 Scaling the virtual netwrk Lad balancing is an example f a netwrk middlebx Eg., intrusin detectin sftware, prtcl acceleratrs, etc Services that frward r mutate a netwrk flw Scaling middlebxes is ften verlked, but may need its wn tier Especially if the functin can be CPU intensive (ie., intrusin detectin) Basic apprach: split the flws Eg. OpenFlw allws netwrk switches t have flws defined & switched Lad balancing the lad balancers Wrking with netwrk switches & ruters facilitates bandwidth allcatin as well Feb 6, Adv. Clud Cmputing 15

16 Next up Next lecture will be n Prgramming Framewrks, part 2 After that we will delve int clud strage systems Feb 6, Adv. Clud Cmputing 16

Using SPLAY Tree s for state-full packet classification

Using SPLAY Tree s for state-full packet classification Curse Prject Using SPLAY Tree s fr state-full packet classificatin 1- What is a Splay Tree? These ntes discuss the splay tree, a frm f self-adjusting search tree in which the amrtized time fr an access,