Google App Engine

Google App Engine is a platform for developing and hosting web applications on Google's servers. This makes it one of the so-called Platform-as -a- service area (PaaS ). The service is free under certain restrictions on the amount of resources used. The limitations of the free version Free include:

  • Applications may only use a maximum of 28 CPU hours per day.
  • The pages can be accessed without limits, provided CPU hours and traffic are still available.
  • It may be 1 GB of data stored in the High Replication Datastore.
  • With the Mail API than 100 mails per day may be sent.
  • The incoming and outgoing traffic must not exceed a maximum of 1GB per day.

More resources are zukaufbar. Is billed according to the actual consumption. With a paid ( "paid " or "premium account" ), these restrictions do not apply.

  • 2.1 Communication Example
  • 2.2 Application Availability

Development environment

It is Python 2.5.2 and 2.7, available since April 2009, the Java VM with all the languages ​​that have been implemented for this ( Clojure, Groovy, Scala, JRuby, and; official Grails Support announced for Grails v1.1.1 ) Go was in May 2011 listed as another supported language.

Services and technologies

Google App Engine ( GAE ) provides applications for both development environments various services ( "Services ") are provided, which are based on Google technologies, which are also used in other Google applications and services:

Persistence

The "DataStore" is a distributed data storage service with query engine and transaction security, but without relational schemas, based on the Google " BigTable " concept. For Java, in addition to the low-level API also parts of JDO and JPA are supported. Experimental is the relational database Google Cloud SQL.

Authentication

Based on Google Accounts, that is, users with Google account can log on to applications.

URL Fetch

Applications can use the Google infrastructure to access Internet content.

Mail

Applications can send and receive emails through the Google e - mail infrastructure.

Memcache

Should be available in-memory caching for data that need not be stored in the persistence layer, but in several instances of the application. The cache is based on the open source system Memcached.

Image manipulation

Rotate, Flip, Zoom In, Zoom and crop images.

Google Cloud SQL

In October 2011, Google announced a maintenance-free SQL database to support JDBC and DB - API. The service aims to make it possible to use a relational database with App Engine applications. The database engine is MySQL version 5.1.59 and the maximum size of the database must not exceed 10 GB.

Server behavior

Communication example

Application availability

The application is not permanently loaded on a server. To relieve the server, unneeded applications are currently away after 15 minutes from the server or required applications unceremoniously on the server loaded (see "Communication Example"). This counteracts a server overload, but at the same time ensures the availability of each application.

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