1. An Empirical Performance Study of AppEngine and AppScale Fei Dong Yunjia Zhou Xuanran Zong Duke University Duke University Duke University1 Introduction mance of Google AppEngine and AppScale, in par- ticular from a request latency perspective. Second,In recent years, we have witnessed an increasing trend we compare the performance of diﬀerent databasedon cloud computing usage. The prominence of cloud supported by AppScale . By answering thesecomputing comes from its elasticity and “pay-as-you- two questions, we want to have a general sense ofgo” charging model. On one hand, with cloud com- how good/bad is AppScale compared to Google Ap-puting, small enterprises do not need to pay any up- pEngine.front investment on infrastructure and IT staﬀ, sav- The rest of this report will be organized as follows.ing cost and reducing the risk of over-provisioning; on In section 2, we brieﬂy introduce how AppEngine andthe other hand, cloud providers can multiplex work- AppScale works. In section 4, we present our exper-loads from many customers and improve the utiliza- iment framework. In section 3 and 5, we articulatetion of their data centers. how we deploy the system and perform the experi- ment, as well as some results. In the last section, we In general, there are three types of cloud comput- end up with a brief conclusion.ing model: Software as a Service(SaaS), Platform asa service(PaaS) and Infrastructure as a Service(IaaS).Each cloud provider chooses one model to build their 2 Backgroundcloud infrastructure. For example, Amazon EC2 build their cloud model as IaaS, i.e. they rent raw 2.1 Google AppEnginevirtual machines to their customers. On the otherend of the spectrum, Google AppEngine  and Mi- App Engine allows you to deploy your Web applica-crosoft Azure are PaaS, because they merely provide tions to Google’s highly scalable infrastructure. Al-an interface for their customer to host web applica- though the infrastructure is designed to scale, theretions on Google’s data centers. While there are a are a number of ways to optimize the performance ofcouple of public cloud services oﬀered by commercial the application, which results in an improved user ex-companies, academia is also working hard to oﬀer perience and less resource consumption. App Engineopen source cloud services. For instance, UCSB has includes the following features:announced their Eucalyptus , which fully mimicsAmazon EC2, and AppScale , which fully mimics • dynamic web serving, with full support for com-Google Appengine. Therefore, any party who owns mon web technologiesa cluster can become a public cloud provider by de-ploying either Eucalyptus or AppScale on the cluster. • persistent storage with queries, sorting and transactions However, there is a caveat here: although Euca-lytpus and AppScale can mimic the functionalities, • automatic scaling and load balancingdo they also provide the same performance? In thisproject, we tried to answer one small facet of this • APIs for authenticating users and sending emailproblem. First, we attempt to compare the perfor- using Google Accounts
2. • a fully featured local development environment ease the deployment. The users only need to build the that simulates Google App Engine on your com- image from source and deploy the image. Though it puter sounds trivial at the ﬁrst glance, we actually confront a lot of issues when we deploy it on our department’s • task queues for performing work outside of the Eucalyptus cluster. We will further elaborate this in scope of a web request section . • scheduled tasks for triggering events at speciﬁed Once we have deployed AppScale, we can upload times and regular intervals GAE applications to the system. Each application has three major components provided by AppScale to The applications can run in one of two runtime en- serve the request. They are AppServer, data storagevironments: the Java environment, and the Python and AppLoadBalancer(ALB), which are very similarenvironment. Each environment provides standard to the components involved in a 3-tier web system.protocols and common technologies for web applica- The ALB acts like a HTTP server and load balancer.tion development. Each app is allocated resources When it receives request, it redirect the request towithin limits. one AppServer which hosts the application and initi- With App Engine, Google takes care of everything ate the connection. The AppServer is similar to thefor you. The App Engine datastore provides distri- application server in typical web system that it hostsbution, replication, and load-balancing services be- the application and do servelet processing. Lastly,hind the scenes, freeing you up to focus on imple- the data storage stores all the persistent data. App-menting your business logic. App Engine’s data- Scale provides a great ﬂexibility for users to choosestore is powered mainly by two Google services: appropriate back-end database, including HBase, Hy-Bigtable and Google File System (GFS). Bigtable is pertable, Mysql, Cassandra, Voldemort, MongoDB,a highly distributed and scalable service for storing MemcacheDB, Scalaris. More importantly, they alland managing structured data. Bigtable utilizes a shares the same API provided by JDO and users cannon-relationship object model to store entities, allow- run application seamlessly on diﬀerent data storage.ing you to create simple, fast, and scalable applica- In other words, users do not need to make any mod-tions. The datastore also uses GFS to store data and iﬁcation to the code in order to accommodate a newlog ﬁles. GFS is a scalable, faulttolerant ﬁle system back end storage.designed for large, distributed, data-intensive appli-cations. App Engine uses the Java Persistence API(JPA)) and Java Data Objects (JDO) interfaces for 3 Deploymentmodeling and persisting entities. At the beginning, we attempted to build AppScale image from source and launched AppScale instances2.2 AppScale on our local Eucalyptus cluster. We ﬁrst used App-AppScale was developed by UCSB in order to mimic Scale tool to create AppScale image emi-9F410FB6the PaaS cloud model. It oﬀers almost the same on dbc1-03 and ran appscale-run-instances toapplication interface as Google AppEngine. This launch the appscale instance. The command can suc-includes same application structure, same back-end cessfully launch an instance on the Eucalyptus clusterdata storage API (they all use JDO), and very sim- but will be blocked at ’wait for your instance to com-ilar application deployment routine. Therefore, peo- plete the bootup process’. Figure 1 shows the App-ple can switch their application from one to the other Scale log when we execute appscale-run-instances.without any modiﬁcation. From the log we can observe that AppScale have AppScale can be deployed on three platforms: launched two instances running AppScale image onKVM enabled cluster, Eucalyptus, and EC2. App- the Eucalyptus cluster and we can even log in onScale provides a set of command written in Ruby to those instances. Yet, it was blocked by some known
3. $appscale-run-instances --min 1 --max 1 --file sample_apps/guestbook/--machine emi-9F410FB6 --table memcachedb --infrastructure euca --keynamedongfei --instance_type c1.xlarge -v --forceAbout to start AppScale over a cloud environment with the euca tools withinstance type c1.xlarge.----------- repeat the time ----Reported Public IPs: [192.168.1.35]Reported Private IPs: [192.168.1.35]Please wait for your instance to complete the bootup process.New secret key is 1Zu22syYs2jKhs2nTpuKhm2bY2nJuV ft"machine"=>"emi-9F410FB6", "keyname"=>"myapp", "ips"=>"","replication"=>"1", "instance_type"=>"c1.xlarge","ec2_access_key"=>"DK4LXEFhkcYf8vNztq0FhKXEF5mpW15vAinYfw","infrastructure"=>"euca", "table"=>"memcachedb", "min_images"=>"1","ec2_secret_key"=>"cfKFBU35lbdAg8soawO9NcumXQgqqUKh9aOSg", "appengine"=>"3","ec2_url"=>"http://184.108.40.206:8773/services/Eucalyptus","keypath"=>"myapp.key", "hostname"=>"192.168.1.35", "max_images"=>"1"Head node successfully created at 192.168.1.35.It is now starting up memcachedb via the command line arguments given.Generating certificate and private key Copying over credentials for cloudStarting server at 192.168.1.35 Please wait for the controller to finishpre-processing tasks.This AppScale instance is linked to an e-mail address giving it administratorprivileges.Enter your desired administrator e-mail address: [firstname.lastname@example.org]The new administrator password must be at least six characters long and caninclude non-alphanumeric characters.Enter your new password: [xxxxxx]Enter again to verify: [xxxxxx]Please wait for AppScale to prepare your machines for use.[Blocked here]dongfei@dbc1-03:~$ euca-describe-instances |grep emi-9F410FB6INSTANCE i-47D0099E emi-9F410FB6 192.168.1.34 192.168.1.34running cps212 0 c1.xlarge 2010-12-01T04:15:22.934Zdukecs-pod1 eki-0AC4191A eri-59AE1A00 Figure 1: AppScale log during instance launching
4. post preparation work. This is not the correct statusas described in . We changed other conﬁgurationparameters and it still did not work either. We readmost of the online documents of AppScale and didnot ﬁnd any clue. Someone from AppScale mailing suggested us torun appscale-run-instances on master node. Hesaid ’can you try using the AppScale tools that areinstalled on the master node (and if it’s not there Figure 2: Sample benchmark.py outputat /usr/local/appscale-tools, can you install it)? Trya run-instances on the master node and I think thenetworking problems should be ok’. So, we ran the thread is going to pull the job from job queue, exe-command there but found AppScale was still blocked. cutes the job and measures the completion time. InRobin Hood told us ’It seems there are some thing our experiment, we deﬁne job as sending a single re-with your database. The instance need at lease 1GB quest to our web application. After we ﬁnish sendingmemory to start database daemon’. all the requests, the script prints out some statistics, Given the limited amount of time left, we decided such as mean request latency. Figure 2 shows a sam-to give up the Eucalyptus cluster and switch to Ama- ple output produced by running benchmark.py. Notezon EC2. Since EC2 already has a default AppScale that this script is highly generic and extensible. Youimage, we do not have to build our own image. App- can deﬁne you own customized job behavior and useScale runs smoothly on EC2 for all the conﬁguration the same script to conduct experiment.parameters we have tried (diﬀerent databases, dif- We then leverage this test script to send concur-ferent number of instances, etc.). We also attach a rent requests to server in order to saturate the re-log for a successful launch of AppScale image in Ap- quired workload. Note that we cannot use a sin-pendix. gle machine to send requests because that is equiv- alent to using a single commodity desktop to satu- rate a commercial high-performance server. Hence,4 Experiment Framework we employ our department cluster as worker slaves to help us sending concurrent requests and our lo-We have two goals in this project: cal machine acts as a master to coordination all the experiment done on each worker. We use all the • to compare the performance between Google Ap- cluster machines (i.e. from linux1.cs.duke.edu pEngine and AppScale to linux30.cs.duke.edu. Each worker runs • to compare the performance among various benchmark.py with concurrency 10. In total, we have databases provided by AppScale 10 ∗ 30 outstanding concurrent requests to saturate the server workload. In addition, when we run multi- There are all kinds of performance metrics, such ple threads on one worker, we notice a certain amountas throughput, goodput and latency, etc. We se- of overhead depending on the concurrency size. Inlected request latency because this is the one which order to reconcile this overhead, we always fully uti-the cloud users most care about. lize all the threads of one machine before we use the We developed an automatic experiment framework next machine. In this case, we make thread overheadto conduct a series of experiments. We ﬁrst wrote our as a constant. In summary, our framework works ascore test script benchmark.py, which takes conﬁgure follows:parameters such as number of requests, concurrency,etc. The scripts is implemented using a thread pool, 1 The master copies all the experiment relatedthe size of which depends on the concurrency. Each scripts and conﬁguration ﬁles to each worker.
5. 2 The master then issues a command to each 30000 Google Appengine worker simultaneously to invoke benchmark.py Appscale on EC2/one m.large instance Appscale on EC2/two m.large instance 25000 Appscale on EC2/four m.large instance 3 In the end, all the worker returns the experiment Mean request latency (ms) results back to the master which is then in charge 20000 of processing the ﬁnal data. 150004.1 Request Workload 10000We further notice that even though we can leverage 5000thirty workers to send concurrent requests, we stillcannot saturate the server. The reason is that the 0 0 20 40 60 80 100 120 140 160 180 200application we have chosen is too light weighted and # of concurrent requestsdoes not impose too much computation or storageoperations. Therefore, we hack into the application Figure 3: Performance of AppEngine and AppScaleto modify the workload. In our experiment, each re-quest invoke 1000000 ﬂoating point computation and Besides, the AppEngine scales quite well. As theten SQL(select) queries. We claim this can capture number of concurrent request increased, the perfor-both the computation and data processing perfor- mance of AppEngine was pretty stable. The App-mance oﬀered by the cloud services. Scale, however, not so scalable as AppEngine. The We also attempted to measure the performance of latency increased dramatically when we augment thediﬀerent databases provided by AppScale. This in- number of concurrent requests.volves comparing read/write/delete operations sep- Considering the dominant factor that may aﬀectsarately. Hence, we also write our write and delete the scalability, we also evaluate the scalability ofworkload. The write workload involves 1000 data in- AppScale on diﬀerent number of EC2s instances. Assertion SQL queries (write operations). The delete what we can see from ﬁgure 3, the performance of 4workload involves clean all the existing data, which nodes is much better than the 1 node. So, we canis typically just the 1000 data we previously inserted, get a tentative conclusion that, when more instancesin the system. added into the master-slave model, the AppScale can handle more concurrent requests.5 Evaluation It looks like the AppEngine outperformed the App- Scale. However, we still hesitate to claim the conclu-5.1 AppEngine vs AppScale sion, since we have no idea the number of instances run in Google AppEngine. They may have a lot ofIn this experiment, we want to evaluate the scal- machines to respond our concurrent requests, whichability of AppEngine and AppScale with diﬀerent makes them achieve the high scalability. In otheramount of node. words, if we run enough instances on AppScale, the First, we deployed the our modiﬁed application as performance would be stable.mentioned in section 4.1 on both Google AppEngineand AppScale on Amazon EC2 with 1, 2, 4 instances 5.2 Data Storage Performancerespectively. Then, we use our framework to saturatethe server. We send concurrent requests from 10 200 In the experiment, we noticed that the Appscale of-and measured the mean request latency. Figure 3 fers seven diﬀerent database interfaces for the clientshows the performance of each case. to choose. So we decide to evaluate the perfor- As we can see, the mean request latency of Google mance of diﬀerent type of databases when heavyAppEngine is pretty low comparing to the AppScale. write, heavy-read and delete respectively.
6. (a) Write operation (b) Read operation (c) Delete operation Figure 5: Read/Write/Delete operations on two instances work on a single node. From the graph, we notice that there are signiﬁcant performance diﬀerence be- tween diﬀerent databases, e.g. Voldemort and Mon- goDB is much worse than MemcacheDB and Cassan- dra. Therefore, we need to be more wise when we choose which database to use. Figure 5 show the comparison of performance of diﬀerent databases on two instances for the write, read and delete operation respectively. As we can see, the MemcacheDB did quite well, and the latency of Voldemort database is quite long. However, we cannot assert that the Voldemort database is slow and not useful. We refer to some resources to ﬁgure out why it performed not so well. The reason maybe is that it is a distributed database, and not a relational database, which makes sense that Figure 4: Read operations on single instances it is slow. For write, we use 10 threads to concurrently ap- 6 Conclusionpend 500 Bytes data entry to the back-end data stor-age and we are inserting 1000 entries in total. ForIn this project, we did an empirical performanceread, we made the server to do 1M ﬂoating-point study of AppEngine and AppScale. We are interestedcomputation and 10 data queries for a single request. in these two platforms because from the program-In total, we send 100 read requests. For delete, weming interface perspective, AppScale highly mimicjust remove all the existing data. AppEngine API. We want to reveal how much perfor- Figure 4 shows the performance of four databases mance diﬀerence do they have. From our experimentout of seven options on a single instance. We only results, AppScale has much better performance, bothshow four because the rest three databases must be in terms of request latency and scalability. Moreover,deployed on the master-slave model, which cannot we also conducted experiments to compare diﬀerent
7. data storage services provided by AppScale. Our re- A Appendix I: Log from a suc-sults elaborate that diﬀerent storage services actuallyrender dramatically diﬀerent performance. Hence, we cessful instance launchneed to be more wise to choose one to use when we Please refer to ﬁgure 6.host our application on AppScale. In future, besidesthe performance comparison, we may also explore thecost of AppEngine and AppScale and investigate ifwe can sacriﬁce a little performance by saving morecost.References Amazon Elastic Compute Cloud. http://aws.amazon. com/ec2. AppScale Documentation. http://www.google.com/ url?q=http%3A%2F%2Fcode.google.com%2Fp%2Fappscale% 2Fwiki%2FDeploying_AppScale_1_4_via_Eucalyptus% 23Running_a_Sample_Application. Eucalyptus. http://open.eucalyptus.com. Google AppEngine. http://appengine.google.com. Bunch, C., Chohan, N., Krintz, C., Chohan, J., Kupferman, J., Lakhina, P., Li, Y., Nomura, Y., Bunch, C., Kupferman, J., and Krintz, C. An eval- uation of distributed datastores using the appscale cloud platform. Chohan, N., Bunch, C., Pang, S., Krintz, C., Mostafa, N., Soman, S., and Wolski, R. Appscale design and im- plementation, 2009.
8. /usr/local/appscale-tools/bin/appscale-run-instances --min 4 --max 4 --file/home/dongfei/cps212/cps212project/guestbook --machine ami-044fa56d --tablememcachedb --infrastructure ec2 --instance_type m1.large --keynamecps212_2460_0 --forceAbout to start AppScale over a cloud environment with the ec2 tools withinstance type m1.large.Run instances message sent successfully. Waiting for the image to start up.[Sun Dec 12 20:35:56 -0500 2010] 1799.999987 seconds left until timeout...[Sun Dec 12 20:36:19 -0500 2010] 1777.262273 seconds left until timeout.../* time remaining log omitted */[Sun Dec 12 20:40:50 -0500 2010] 1506.176784 seconds left until timeout...[Sun Dec 12 20:41:13 -0500 2010] 1483.592267 seconds left until timeout...[Sun Dec 12 20:41:36 -0500 2010] 1460.731472 seconds left until timeout...Please wait for your instance to complete the bootup process.Head node successfully created at ec2-67-202-41-213.compute-1.amazonaws.com.It is now starting up memcachedb via the command line arguments given.Generating certificate and private keyCopying over credentials for cloudStarting server at ec2-67-202-41-213.compute-1.amazonaws.comPlease wait for the controller to finish pre-processing tasks.This AppScale instance is linked to an e-mail address giving it administratorprivileges.Enter your desired administrator e-mail address:The new administrator password must be at least six characters long and caninclude non-alphanumeric characters.Enter your new password:Enter again to verify:Please wait for AppScale to prepare your machines for use.AppController just startedSpawning up 1 virtual machinesCopying over needed files and starting the AppController on the other VMsSetting up database configuration filesStarting up Load BalancerYour user account has been created successfully.Uploading cps212guestbook...We have reserved the name cps212guestbook for your application.cps212guestbook was uploaded successfully.Please wait for your app to start up.Your app can be reached at the following URL:http://ec2-67-202-41-213.compute-1.amazonaws.com/apps/cps212guestbookThe status of your AppScale instance is at the following URL:http://ec2-67-202-41-213.compute-1.amazonaws.com/status Figure 6: A successful instance launch log