AppScale Talk at SBonRails

The AppScale Project Presented by Chris Bunch (on behalf of the AppScale team) March 7, 2011 @ sbonrails meetupThursday, March 10, 2011

Thursday, March 10, 2011

Overview • Google App Engine • AppScale - now with 50% Ruby! • Research Directions • Neptune - A Ruby DSL for the cloudThursday, March 10, 2011

Google App Engine • A web framework introduced in 2008 • Python and Java supported • Offers a Platform-as-a-Service: Use Google’s APIs to achieve scale • Upload your app to GoogleThursday, March 10, 2011

QuotasThursday, March 10, 2011

Data Model • Not relational - semi-structured schema • Compare to models in Rails • Exposes a get / put / delete / query interfaceThursday, March 10, 2011

Storing Data • Datastore API - Persistent storage • Memcache API - Transient storage • User can set expiration times • Blobstore API - Store large ﬁles • need to enable billing to use itThursday, March 10, 2011

Be Social! • Mail API - Send and receive e-mail • XMPP API - Send and receive IMs • Channel API - Creating persistent connections via XMPP • Use for chat rooms, games, etc.Thursday, March 10, 2011

Background Tasks • Cron API - Access a URL periodically • Descriptive language: “every 5 minutes”, “every 1st Sun of Jan, Mar, Dec”, etc. • Uses a separate cron.yaml ﬁle • Taskqueue API - Within your app, ﬁre off tasks to be done laterThursday, March 10, 2011

Dealing with Users • Users API: Uses Google Accounts • Don’t write that ‘forgot password’ page ever again! • Authorization: via app.yaml: • anyone, must login, or admin onlyThursday, March 10, 2011

When Services Fail • Originally: failures throw exceptions • Just catch them all! • Capabilities API: Check if a service is available • Datastore, Memcache, and so onThursday, March 10, 2011

Deploying Your App • Develop locally on SDK • Stub implementations of most APIs • Then deploy to GoogleThursday, March 10, 2011

How to Scale • Limitations on the programming model: • No ﬁlesystem interaction • 30 second limit per web request • Language libraries must be on whitelist • Sandboxed executionThursday, March 10, 2011

Enter AppScale • App Engine is easy to use • but we really want to tinker with the internals! • Need an open platform to experiment on • test API implementations • add new APIsThursday, March 10, 2011

Enter AppScale • Lots of NoSQL DBs out there • Hard to compare DBs • Conﬁguration and deployment can be complex • Need one-button deploymentThursday, March 10, 2011

Storing Data • Datastore API - AppServers use a database agnostic layer - sends requests to PBServer • Named for data format: Protocol Buffers • Memcache API - memcached • Blobstore API - Custom serverThursday, March 10, 2011

Be Social! • Mail API - sendmail (disabled by default) • XMPP API - ejabberd • Channel API - strophejsThursday, March 10, 2011

Background Tasks • Cron API - Uses Vixie Cron • Taskqueue - Separate thread fetches web page • Both make a single attempt • Will replace with distributed, fault- tolerant versionsThursday, March 10, 2011

Dealing with Users • Users API: Defers users to AppLoadBalancer • Password reset via command-line tools • Authorization: no major changes hereThursday, March 10, 2011

Deploying Your App • Develop locally on SDK • Stub implementations of most APIs • Then deploy to AppScale! • Use your own cluster or via Amazon • Command-line tools mirror Amazon’sThursday, March 10, 2011

Deploying Your App • run-instances: Start AppScale • describe-instances:View cloud metadata • upload-app: Deploy an App Engine app • remove-app: Un-deploy an App Engine app • terminate-instances: Stop AppScaleThursday, March 10, 2011

Deployment Models • Cloud deployment: Amazon EC2 or Eucalyptus (the open source implementation of the EC2 APIs) • Just specify how many machines you need • Non-cloud deployment via Xen or KVMThursday, March 10, 2011

Thursday, March 10, 2011

AppController • The brains of the outﬁt • Runs on every node • Handles conﬁguration and deployment of all services (including other AppControllers) • Written in RubyThursday, March 10, 2011

Load balancer • Routes users to their app via nginx • haproxy makes sure app servers are live • Can’t assume the user has DNS: • Thus we wrote the AppLoadBalancer • Rails app that routes users to apps • Performs authentication as wellThursday, March 10, 2011

AppLoadBalancerThursday, March 10, 2011

App Server • We modiﬁed the App Engine SDK • Easier for Python (source included) • Harder for Java (had to decompile) • Removed non-scalable API implementations • Goal: Use open source whenever possibleThursday, March 10, 2011

A Common Feature RequestThursday, March 10, 2011

Database Options • Open source / open APIs / proprietary • Master / slave v. peer-to-peer • Differences in query languages • Data model (key/val, semi-structured) • In-memory or persistent • Data consistency model • Interfaces - REST / Thrift / librariesThursday, March 10, 2011

In AppScale: • BigTable clones: • Master / slave relationship • Master stores metadata • Slaves store data • Fault-tolerant to slave failure • Partially tolerant to master failureThursday, March 10, 2011

In AppScale: • Variably consistent DBs • Voldemort and • Both are peer-to-peer: no SPOF • Voldemort: Specify consistency per table • Cassandra: Specify consistency per requestThursday, March 10, 2011

In AppScale: • Relational: • Not NoSQL but used like NoSQL • Document-oriented: • Targets append-heavy workloadsThursday, March 10, 2011

In AppScale: • Key-value datastores: • MemcacheDB: like memcached but persistent and replicated • Scalaris: in-memory, no persistence • SimpleDB: semi-structured but used as key-value (will update this in the future)Thursday, March 10, 2011

Research Ideas • Placement support • Monitoring • Shared memory • Cost modeling • Hybrid cloud • Active Cloud DB • Disaster Recovery • NeptuneThursday, March 10, 2011

Placement SupportThursday, March 10, 2011

MonitrThursday, March 10, 2011

Shared memory • Since AppServer + DB are co-located, reduce message overhead • no serialization • Leverage CoLoRs to do so across languages • AS is in Python or Java, DBS is Python • Can be orders-of-magnitude fasterThursday, March 10, 2011

Cost modeling • Can we reproduce Google’s cost model? • We can reproduce memory, network bandwidth in / out, size and types of data • Can’t reproduce CPU - it’s based on Google’s load, which we can’t capture • varies based on placement and time of dayThursday, March 10, 2011

Hybrid CloudThursday, March 10, 2011

Database Agnostic Transactions • Want to support disparate DBs with ACID • Leverage ZooKeeper for versioning • And PBServer as the DB agnostic layer • Needs strong consistency from DB itself • And row-level atomicity on updatesThursday, March 10, 2011

Active Cloud DB • Need a common interface to DBs • But not just for Java / Python • Named after Rails’ ActiveRecord • Exposes REST interface for DB • Included in AppScale 1.3Thursday, March 10, 2011

Disaster Recovery • People are using App Engine as a production level environment • Need a way to automatically back up data • Can leverage this data for data analytics • Need to also seamlessly switch to AppScale version if App Engine version goes downThursday, March 10, 2011

Neptune • Need a simple way to run compute-intensive jobs • We have the code from the ‘net • We have the resources - the cloud • But the average user does not have the know how • Our solution: create a domain speciﬁc language for conﬁguring cloud apps • Based on RubyThursday, March 10, 2011

Syntax • It’s as easy as: neptune :type => “mpi”, :code => “MpiNQueens”, :nodes_to_use => 8, :output => “/mpi/output-1.txt”Thursday, March 10, 2011

Neptune Supports: • Message Passing Interface (MPI) • MapReduce • Uniﬁed Parallel C (UPC) • X10 • ErlangThursday, March 10, 2011

Extensibility • Experts can add support for other computational jobs • Biochemists can run simulations via DFSP and dwSSA • Embarassingly parallel Monte Carlo simulationsThursday, March 10, 2011

Compiling Code • You may not have the binaries, so compile from source! • Auto-generates makeﬁles for beginners neptune :type => “compile”, :code => “/home/appscale/mpi_nqueens”Thursday, March 10, 2011

Installing Neptune • Just use good old ‘gem’: • gem install neptune • Current version is 0.0.4, fully compatible with AppScale 1.5 • More info at our web page: • http://neptune-lang.orgThursday, March 10, 2011

Wrapping It Up • Thanks to the AppScale team, especially: • Co-lead Navraj Chohan and advisor Professor Chandra Krintz • Check us out on the web: • http://appscale.cs.ucsb.edu • http://code.google.com/p/appscaleThursday, March 10, 2011

AppScale Talk at SBonRails

by Chris Bunch

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