Varaprasad-Go

Google’s Go Language for
Cloud Computing
Presented By:
Suby Gopalan
Yashashwini Adiga
Hem Singh Chouhan
Niranjan Singh
Piyush Mishra

Agenda of the Session
All about ‘GO’
Google App Engine
App Engine Modules
Storing data in Go
Go Service APIs
A fully functional Go App covered via
Demo

Subjective Analysis
Flaws in the existing languages like C++, Java

All about ‘GO’
Why one more programming language ?
Is ‘GO’ an object-oriented language?
Why do garbage collection? Won't it be too
expensive?
Why is the syntax so different from C?
Why is there no pointer arithmetic?

Features of ‘GO’ at a glance
Concurreny and Garbage collection
Has pointers but no pointer arithmatic
Support for networked and multicore
programming
Very fast
Semicolons are not used

Google App Engine
Platform as a Service
Tools you know and Love
Used by millions
Build and Deploy
Scale

Overview of App Engine Features
General Availability
Preview
Experimental
Third Party

Google App Engine for Go
Introduction
Selecting the Go runtime
Organizing Go apps
The sandbox
The Go SDK and tools

Instance scaling and class
Manual, Basic, Automatic
Uploading modules
cd simple-sample
goapp deploy default/app.yaml
goapp deploy mobile-frontend/mobile-frontend.
yaml
goapp deploy static-backend/my-module.
yaml
Monitoring resource usage
Logging

Storing data in GO
Highly reliable and covered by the App
Engine SLA.
ACID transactions.
Advanced querying features.
High availability of reads and writes.
Strong consistency for reads and ancestor
queries.
Eventual consistency for all other queries

Google Cloud SQL
Is a web service that allows you to create,
configure, and use relational databases that
live in Google's cloud.
 It is a fully-managed service offering the
capabilities of a MySQL database, allowing
you to focus on application development.
Alternative Storage Solutions..
BLOBSTORE API Google Cloud Storage is
recommended over using the Blobstore API.

Go Service APIs and Capabilities
import "appengine/capability“

Important Players
CHANNEL
Javascript client
The server
Tokens

Life of a typical channel message
Interaction with Server

Tracking Client Connections
import "appengine/channel"
POSTs to /_ah/channel/connected/
POSTs to /_ah/channel/disconnected/

Examples of API
 Channel Go API - (channel.Create)
The Channel API creates a persistent connection
between your application and Google servers,
allowing your application to send messages to
JavaScript clients in real time without the use of
polling
 Images Go API
The Images Go API provides the ability to serve
images directly from Blobstore, and to optionally
resize or crop those images on the fly.
Image formats
Serving and re-sizing images from the Blobstore

Examples of API
 Logs Go API
Request Log, Application Log
 Mail Go API - import"appengine/mail“
App Engine applications can send email messages on
behalf of the app's administrators, and on behalf of
users with Google Accounts.
Apps can receive email at various addresses.
 Apps send messages using the Mail service and
receive messages in the form of HTTP requests
initiated by App Engine and posted to the app.

Examples of API
 Memcache Go API
– import appengine/memcache“
 NameSpace API
- The Namespaces API in Google App Engine makes it
easy to compartmentalize your Google App Engine
data. This API is implemented via the ,
appengine.Namespacefunction and is incorporated
in certain namespace-enabled APIs.

OAuth for GO
 OAuth is a protocol that allows a user to grant a third party limited
permission to access a web application on her behalf, without sharing
her credentials (username and password) with the third party.
 To initiate the authorization process on behalf of a user, a consumer
calls an OAuth endpoint to get a request token(Valid for 10 mins)
 Once the consumer has a request token, it must direct the user to sign
in using Google Accounts and authorize the consumer to access the
service provider on her behalf.
 Once authorized, the consumer calls the service provider to get
an access token
 The consumer includes this token with all requests to the application's
web service endpoints.

Users GO API
import"appengine/user"
package user provides a client for app
engine's user authentication service.
user represents a user of the application.
func (*User) String
String returns a displayable name for the user

XMPP GO API
 An App Engine application can send and receive chat messages to and
from any XMPP-compatible chat messaging service, such as Google Talk.
 An app can send and receive chat messages, send chat invites, request a
user's chat presence and status, and provide a chat status. Incoming XMPP
messages are handled by request handlers, similar to web requests.
 Sending chat messages
 /_AH/XMPP/MESSAGE/CHAT/
 Receiving chat messages
 app engine makes an http post request to the following url path when
your app receives a chat
 -MESSAGE:/_AH/XMPP/MESSAGE/CHAT/
 -to handle incoming messages, you simply create a request handler that
accepts post requests at this url path.

Handling User Presence
Enabling the xmpp_presence inbound service allows your
application to detect changes to a user's chat presence. When you
enable xmpp_presence, your application receives posts to the
following URL paths:
-Posts to /_ah/xmpp/presence/available/ signal that the user is
available and provide the user's chat status.
-Posts to /_ah/xmpp/presence/unavailable/ signal that the user is
unavailable.
-Posts to /_ah/xmpp/presence/probe/ request a user's current
presence.

Other Important Parts of Go
Configuration
Tools

Varaprasad-Go

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