View source for Google App Engine

{{Short description|Cloud-based web application hosting service}}
{{Use American English|date=December 2022}}
{{Use mdy dates|date=December 2022}}

{{Update|inaccurate=y|date=July 2024}}
{{Infobox software
| name                   = Google App Engine
| title                  = 
| logo                   = File:Logo of Google App Engine.png
| screenshot             = <!-- [[File: ]] -->
| caption                = 
| collapsible            = 
| author                 = 
| developer              = [[Google]]
| released               = {{start date and age|2008|4|7}}<ref>{{cite web |title=Introducing Google App Engine + our new blog |url=http://googleappengine.blogspot.com/2008/04/introducing-google-app-engine-our-new.html |website=Google App Engine Blog |access-date=December 3, 2019 |date=April 7, 2008}}</ref>
| discontinued           = 
| latest release version = 
| latest release date    = 
| latest preview version = 
| latest preview date    = <!-- {{Start date and age|YYYY|MM|DD|df=yes/no}} -->
| size                   = 
| language               = 
| genre                  = [[Platform as a service]]
| website                = {{URL|https://cloud.google.com/appengine/}}
}}
'''Google App Engine''' (also referred to as '''GAE''' or '''App Engine''') is a [[cloud computing]] [[platform as a service|platform used as a service]] for developing and hosting [[web application]]s. Applications are [[Sandbox (computer security)|sandbox]]ed and run across multiple Google-managed servers.<ref>{{cite web|url=https://code.google.com/appengine/docs/python/runtime.html |title=Python Runtime Environment - Google App Engine - Google Code |date=February 22, 1999 |access-date=February 14, 2012}}</ref> GAE supports automatic scaling for web applications, allocating more resources to the web application as the amount of requests increases.<ref>{{cite book |last=Sanderson |first=Dan |title=Programming Google App Engine: Build and Run Scalable Web Apps on Google's Infrastructure |publisher=[[O'Reilly Media]] |year=2009 |isbn=978-0-596-52272-8 |url=https://archive.org/details/programminggoogl0000sand }}</ref> It was released as a [[Preview for Developers|preview]] in April 2008 and launched officially in September 2011.

Applications written in [[Go (programming language)|Go]], [[PHP]], [[Java (programming language)|Java]], [[Python (programming language)|Python]], [[Node.js]], [[.NET Framework|.NET]], and [[Ruby (programming language)|Ruby]] are supported by the App Engine, and other languages can be supported at an additional cost.<ref name="Google App Engine Documentation | App Engine Documentation">{{cite web |title=Google App Engine Documentation {{!}} App Engine Documentation |url=https://cloud.google.com/appengine/docs/ |website=Google Cloud |access-date=December 3, 2019 |language=en}}</ref> The free version of the service offers a standard environment with limited resources. Fees are charged for additional storage, [[Bandwidth (computing)|bandwidth]], or instance hours.<ref>{{cite web|url=https://cloud.google.com/appengine/docs/quotas |title=Quotas - Google App Engine - Google Code |date=February 22, 1999 |access-date=February 14, 2012}}</ref>

==Features==

Google App Engine primarily supports [[Go (programming language)|Go]], [[PHP]], [[Java (programming language)|Java]], [[Python (programming language)|Python]], [[Node.js]], [[.NET Framework|.NET]], and [[Ruby (programming language)|Ruby]] applications, although it can also support other languages via "custom runtimes".<ref name="Google App Engine Documentation | App Engine Documentation" />

Python web frameworks that run on Google App Engine include [[Django (Web framework)|Django]], [[CherryPy]], [[Pylons project#Pyramid|Pyramid]], [[Flask (programming)|Flask]], and [[web2py]] as well as a Google-written web app framework and several others designed specifically for the platform that was created after the release.<ref>{{cite web|url=https://code.google.com/p/tipfy/wiki/AppEngineFrameworks |title=AppEngineFrameworks - tipfy - The almighty little framework for Google App Engine - Google Project Hosting |access-date=February 14, 2012}}</ref> Any Python framework that supports the [[Web Server Gateway Interface|WSGI]] using the CGI adapter can be used to create an application, and the framework can be uploaded with the developed application. Third-party libraries written in Python may also be uploaded.<ref>{{cite web|url=https://cloud.google.com/appengine/docs/whatisgoogleappengine?csw=1 |title=What Is Google App Engine? - Google App Engine - Google Code |date=February 22, 1999 |access-date=February 14, 2012}}</ref><ref>{{cite web|url=https://cloud.google.com/appengine/docs/python/tools/webapp/ |title=webapp Overview - Google App Engine - Google Code |date=February 22, 1999 |access-date=February 14, 2012}}</ref>

SDK version 1.2.2 added support for bulk downloads of data using Python.<ref>{{cite web|url=https://cloud.google.com/appengine/docs/adminconsole/datastoreadmin?csw=1#backup_and_restore |title=Uploading and Downloading Data - Google App Engine - Google Code |date=February 22, 1999 |access-date=February 14, 2012}}</ref>

App Engine's integrated [[Google Cloud Datastore]] database has a [[SQL]]-like syntax called "[[Google Cloud Datastore#GQL|GQL]]" ([[Google Query Language]]). GQL does not support the [[Join (SQL)|join]] statement.<ref>{{cite web |date=April 7, 2008 |title=Campfire One: Introducing Google App Engine (pt. 3) |url=https://www.youtube.com/watch?v=oG6Ac7d-Nx8 |via=YouTube}}</ref> Instead, one-to-many and many-to-many relationships can be accomplished using {{code|ReferenceProperty()}}.<ref>{{cite web|url=https://code.google.com/appengine/articles/modeling.html |title=Modeling Entity Relationships - Google App Engine — Google Developers |date=June 26, 2012 |access-date=July 17, 2012}}</ref>

[[Firebase|Google Cloud Firestore]] is the successor to Google Cloud Datastore and replaces GQL with a document-based query method that treats stored objects as collections of documents. Firestore was launched in October 2017.<ref>{{Cite web|url=https://techcrunch.com/2017/10/03/google-launches-cloud-firestore-a-new-document-database-for-app-developers |title=Google launches Cloud Firestore, a new document database for app developers|website=TechCrunch|date=3 October 2017 |access-date=2018-07-16}}</ref>

===Backends===
In [[Google I/O]] 2011, Google announced ''App Engine Backends'', which were allowed to run continuously and consume more memory.<ref>{{YouTube|id=-kepYfCBg6w||title=Google I/O 2011: App Engine Backends}}</ref><ref>{{cite web|url=https://cloud.google.com/appengine/docs/python/backends/?csw=1|title=Backends Python API Overview - App Engine standard environment for Python - Google Cloud Platform|website=Google Cloud Platform}}</ref> The Backend API was deprecated as of March 13, 2014, in favor of the Modules API.<ref>{{cite web|url=https://cloud.google.com/appengine/docs/python/backends/|title=Backends Python API Overview - App Engine standard environment for Python - Google Cloud Platform|website=Google Cloud Platform}}</ref> The Modules API introduced finer control over scaling, versioning, and resource allocation, allowing developers to run different parts of an application with distinct performance settings.<ref>{{Cite web |title=Using the Modules API {{!}} Google App Engine standard environment docs |url=https://cloud.google.com/appengine/docs/standard/services/modules |access-date=2025-02-16 |website=Google Cloud |language=en}}</ref>

===Google Cloud SQL===
In October 2011, Google previewed a zero-maintenance SQL database, which supports JDBC and DB-API.<ref>{{cite web|url=http://googlecode.blogspot.com/2011/10/google-cloud-sql-your-database-in-cloud.html|title=Google Cloud SQL: your database in the cloud - The official Google Code blog|date=October 6, 2011}}</ref> This service allows creating, configuring, and using relational databases with App Engine applications. Google Cloud SQL supports MySQL 8.0, 5.7, and 5.6.<ref>{{cite web|url=https://cloud.google.com/sql/docs/features|title=Cloud SQL Features - Cloud SQL Documentation - Google Cloud Platform|website=Google Cloud Platform}}</ref>

===Restrictions===
*Developers have read-only access to the file system on App Engine. Applications can use only virtual file systems.
*App Engine can only execute code called from an HTTP request (scheduled background tasks allow for self-calling HTTP requests).
*Users may upload arbitrary Python modules, but only if they are pure Python. [[C (programming language)|C]] and [[Pyrex (programming language)|Pyrex]] modules are not supported.
*Java applications may only use a subset (The JRE Class White List) of the classes from the JRE standard edition.<ref name="google1">{{cite web|url=https://cloud.google.com/appengine/docs/java/jrewhitelist |title=The JRE Class White List - Google App Engine - Google Developers |date=February 22, 1999 |access-date=June 14, 2013}}</ref> This restriction does not exist with the App Engine Standard Java8 runtime.
*A process started on the server to answer a request can't last more than 60 seconds (with the 1.4.0 release, this restriction does not apply to background jobs anymore).
*Does not support sticky sessions (a.k.a. session affinity), only replicated sessions are supported including limitation of the amount of data being serialized and time for session serialization.

===Application hosting===

While other services let users install and configure nearly any *NIX compatible software, App Engine requires developers to use only its [[Google App Engine#Supported programming languages and frameworks|supported languages, APIs, and frameworks]]. Current APIs allow storing and retrieving data from the document-oriented [[Google Cloud Datastore]] database, making HTTP requests, sending e-mail, manipulating images, and caching. Google Cloud SQL<ref>{{cite web|url=https://cloud.google.com/sql/docs|title=Google Cloud SQL Databases - Cloud SQL - Google Cloud Platform|website=Google Cloud Platform}}</ref> can be used for App Engine applications requiring a relational [[MySQL]] compatible database backend.<ref>{{cite web|url=https://cloud.google.com/appengine/docs/java/cloud-sql/|title=Using Google Cloud SQL - App Engine standard environment for Java - Google Cloud Platform|website=Google Cloud Platform}}</ref>

Per-day and per-minute quotas place restrictions on bandwidth and CPU use, number of requests served, number of concurrent requests, and calls to the various APIs. Individual requests are terminated if they take more than 60 seconds or return more than 32MB of data.

==Portability concerns==
Developers worry that the applications will not be portable from App Engine and fear being locked into the technology.<ref>{{cite web|last=Gallagher |first=Sean |url=https://arstechnica.com/old/content/2008/04/analysis-google-app-engine-alluring-will-be-hard-to-escape.ars |title=Analysis: Google App Engine alluring, will be hard to escape |publisher=Ars Technica |date=April 9, 2008 |access-date=July 17, 2012}}</ref> In response, there are a number of projects to create open-source back-ends for the various proprietary/closed APIs of the app engine, especially the datastore.

[[AppScale]] automatically deploys and scales unmodified Google App Engine applications over popular public and private cloud systems and on-premises clusters.<ref>[https://techcrunch.com/2013/06/24/appscale-launches-as-an-open-source-backup-equivalent-to-google-app-engine/ AppScale Launches As An Open-Source Backup Equivalent To Google App Engine]. TechCrunch (June 24, 2013). Retrieved on 2013-09-18.</ref> It can run Python, Java, PHP, and Go applications on EC2, Google Compute Engine, Azure, and other cloud vendors.

The [[Web2py]] web framework offers migration between SQL Databases and Google App Engine, however, it doesn't support several App Engine-specific features such as transactions and namespaces.<ref>[http://web2py.com/book/default/section/11/13] {{webarchive|url=https://web.archive.org/web/20100220195348/http://web2py.com/book/default/section/11/13|date=February 20, 2010}}</ref>

[[Kubernetes]] is an open-source job control system invented by Google to abstract away the infrastructure so that open-source (e.g. Docker) containerized applications can run on many types of infrastructure, such as [[Amazon Web Services]], [[Microsoft Azure]], and others.

==Usage quotas==
Google App Engine requires a Google account to get started, and an account may allow the developer to register up to 25 free applications and an unlimited number of paid applications.<ref>{{Cite web|title = Google App Engine General Questions|url = https://cloud.google.com/appengine/kb/general#create|website = Google Developers|access-date = June 18, 2015}}</ref>

Google App Engine defines usage quotas for free applications. Extensions to these quotas can be requested, and application authors can pay for additional resources.<ref name="Quotas">{{cite web | url = https://cloud.google.com/appengine/docs/quotas | title = Understanding Application Quotas with Google App Engine | access-date = April 16, 2010}}</ref>

==See also==<!-- New links in alphabetical order please -->
{{Div col|colwidth=20em}}

* [[AWS Elastic Beanstalk]]
* [[Google Apps Script]]
* [[Google Cloud Platform]]
* [[Heroku]]
* [[Microsoft Azure]]
* [[Oracle Cloud#Platform as a Service (PaaS)|Oracle Cloud Platform]]
* [[Rackspace Cloud]]
* [[VMware]]
{{Div col end}}

==References==
{{Reflist|2}}

==Bibliography==
{{Refbegin}}
*{{citation
| first1    = Dan 
| last1     = Sanderson
| date      = October 26, 2012
| title     = Programming Google App Engine
| edition   = 2nd
| publisher = [[O'Reilly Media]]
| page      = 536
| isbn      = 978-1449398262
| url       = http://shop.oreilly.com/product/0636920017547.do
}}
*{{citation
| first1    = Adriaan 
| last1     = de Jonge
| date      = October 31, 2011
| title     = Essential App Engine: Building High-Performance Java Apps with Google App Engine
| edition   = 1st
| publisher = [[Addison-Wesley Professional]]
| page     = 304
| isbn      = 978-0-321-74263-6
| url       = http://www.informit.com/store/product.aspx?isbn=0132484781
}}
*{{citation
| first1    = Daniel 
| last1     = Guermeur 
| first2    = Amy 
| last2     = Unruh 
| date      = November 24, 2010
| title     = Google App Engine Java and GWT Application Development
| edition   = 1st
| publisher = [[Packt Publishing]]
| page     = 480 
| isbn      = 978-1-84969-044-7
| url       = https://www.packtpub.com/google-app-engine-java-and-gwt-application-development/book
}}
*{{citation
| first1    = Kyle
| last1     = Roche
| first2    = Jeff
| last2     = Douglas
| date      = December 31, 2009
| title     = Beginning Java Google App Engine
| edition   = 1st
| publisher = [[Apress]]
| page     = 375 
| isbn      = 978-1-4302-2553-9
| url       = http://www.apress.com/9781430225539
}}
*{{citation |first1    = Dan
 |last1     = Sanderson
 |date      = November 23, 2009
|title     = Programming Google App Engine
 |edition   = 1st
 |publisher = [[O'Reilly Media]]
 |page      = [https://archive.org/details/programminggoogl0000sand/page/400 400]
 |isbn      = 978-0-596-52272-8
 |url       = https://archive.org/details/programminggoogl0000sand/page/400
}}
*{{citation |first1    = Charles
 |last1     = Severance
 |date      = May 22, 2009
|title     = Using Google App Engine
 |edition   = 1st
 |publisher = [[O'Reilly Media]]
 |page      = [https://archive.org/details/usinggoogleappen0000seve/page/262 262]
 |isbn      = 978-0-596-80069-7
 |url       = https://archive.org/details/usinggoogleappen0000seve/page/262
}}
*{{citation
| first1    = Eugene 
| last1     = Ciurana
| date      = February 2, 2009
| title     = Developing with Google App Engine
| edition   = 1st
| publisher = [[Apress]]
| page     = 164
| isbn      = 978-1-4302-1831-9
| url       = http://www.apress.com/9781430218319
}}
{{Refend}}

==External links==
*[https://cloud.google.com/appengine/ Official marketing page]
*{{Official website|https://cloud.google.com/appengine/docs}}
*[http://googlecloudplatform.blogspot.com/ Official Google Cloud Platform Blog]
*[https://code.google.com/p/googleappengine/wiki/SdkReleaseNotes Release notes]
*[http://www.stanford.edu/class/ee380/Abstracts/081105.html Google App Engine - Run your web applications on Google's infrastructure] - a technical talk by Google engineer [[Guido van Rossum]] at [[Stanford University]]. ([https://web.archive.org/web/20090326060917/http://stanford-online.stanford.edu/courses/ee380/081105-ee380-300.asx online video archive])
*[http://blog.adjutas.com/index.php/2017/01/27/benefits-of-adopting-google-app-engine/ Benefits of adopting Google App Engine] {{Webarchive|url=https://web.archive.org/web/20170202052421/http://blog.adjutas.com/index.php/2017/01/27/benefits-of-adopting-google-app-engine/ |date=February 2, 2017 }}
*[http://blog.adjutas.com/index.php/2016/11/24/using-an-external-database-with-google-app-engine/ Using an external database with Google App Engine] {{Webarchive|url=https://web.archive.org/web/20170806115611/http://blog.adjutas.com/index.php/2016/11/24/using-an-external-database-with-google-app-engine/ |date=August 6, 2017 }}
*[https://web.archive.org/web/20090416214549/http://spreadsheets.google.com/pub?key=pRJ_0hajVrhacLjp3HqD5ew Java Frameworks and libraries supported]
*[https://web.archive.org/web/20100220195348/http://web2py.com/book/default/section/11/13 Web2py book -- online documentation -- Google App Engine deployment recipe]
*[https://code.google.com/p/cloudsql/ Google Cloud SQL Sample Projects]
*[https://cloud.google.com/solutions/nodejs/ Google Cloud supports node.js]
*[https://github.com/jacobcui/appmd '''Appmd''': Python development sample project. App Engine/django/Google Closure/Endpoints/Material design ]

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[[Category:Google services|App Engine]]
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