jdkio: java ee 8 what servlet 4 and http2 mean to you

Alex Theedom @readlearncode

Java EE 8:

What Servlet 4.0 and

HTTP/2 mean?

@readlearncode readlearncode.com

Who am I?

Alex Theedom

Author

Trainer

Blogger

Speaker

What’s on?


• Why Do We Need HTTP/2

• Workarounds to HTTP1.1

• HTTP Sockets

• Topline HTTP/2 Features

• Servlet 4.0 Features

• Server Support

• Status Update

• Extract Bits

• Q&A

What’s on?

Why Do We Need HTTP/2?


• Increase perceived performance of web

• HTTP protocol not suitable

• Since May 2012 web page size increased 250%

• The problem with HTTP/1.1

Source: HTTPArchive.com

Why Do We Need HTTP/2?The Goal of HTTP/2


• Requests resources in parallel HTTP 1.0

• One request per TCP connection

• HTTP1.1 Pipelining: multiple requests

• Responds in sequence

• Delay causes head-of-line blocking

How a browser loads a webpage?

open

close

client server

no pipelining

index.html

style_1.css

logo.jpg

open

close

client server

pipelining

time

index.html

style_1.css

logo.jpg

Why Do We Need HTTP/2?

Workarounds


• Multiple connections

• Acceptable but has issues

• TCP sockets expensive

• Browser max connections

Workarounds to HTTP1.1Solution to Head-Of-Line Blocking

open

close

client server

connection 1

style_1.css

open

close

client server

connection 2

javaScript_1.js

open

close

client server

connection 3

image_1.png


Workarounds to HTTP1.1CSS/JavaScript File Concatenation

background.css

header.css

menu.css

style.css


Workarounds to HTTP1.1CSS and JavaScript Inlining

…


• Embed image in web page

• Base 64 encoded

• Time spent decoding

• Caching difficult

Workarounds to HTTP1.1Inlined Assets


• One image file consists of many smaller images

Workarounds to HTTP1.1Image Sprite Sheet

Image sprites from Amazon, Google and Facebook.


Workarounds to HTTP1.1Domain Sharding

web page

y.example.com

x.example.com

domain 2

domain 1

logo.jpg

icon.jpg

header.css

menu.css

HTTP Sockets


• Not much specified

• Two maximum open sockets (ignored by browsers)

• Throw away resources

HTTP SocketsWhat HTTP1.1 Says About Sockets


• Much is specified

• Scares resources

• Only open one socket

HTTP SocketsWhat HTTP/2 Says About Sockets

Topline HTTP/2 Features


• HTTP/2 is comprised of two specifications

• Hypertext Transfer Protocol version 2 - RFC7540

• HPACK - Header Compression for HTTP/2 - RFC7541

• Binary Protocol Based on Frames

Topline HTTP/2 FeaturesWhat’s new


• Request/Response Multiplexing

• Binary Framing

• Header Compression

• Stream Prioritization

• Server Push

Topline HTTP/2 FeaturesFeatures


• Most important feature• Request and response is multiplexed

• Fully bi-directional communication

• Concepts• Connection - A TCP socket

• Stream – A channel of communication

• Message – A request/response and control message

• Frame –The smallest unit within a communication

• Resolves head-of-line blocking

Topline HTTP/2 FeaturesRequest/Response Multiplexing


• Hierarchical structure of logical communication blocks


connection

stream

frame frame frame

frame frame frame

message

stream

frame frame frame

frame frame frame

message

frame frame frame

frame frame frame

message

stream

frame frame frame

frame frame frame

message

frame frame frame

frame frame frame

message

frame frame frame

frame frame frame

message


• Interweave the logical stream over a single TCP



• Decomposition of the frame

• Type fields can be• HEADERS corresponds to the HTTP headers

• DATA corresponds to the HTTP request body

• PUSH_PROMISE server notifies of push intent

• RST_STREAM notifying error, client rejects push

• PRIORITY specifies stream priority

• SETTING, PING, GOAWAY, WINDOW_UPDATE, CONTINUATION

Topline HTTP/2 FeaturesBinary Framing


• Mapping the HTTP Request to Frames

Topline HTTP/2 FeaturesHeader Compression

HTTP request Header Frame

GET /index.html HTTP/1.1

Host: example.com

Accept: text/html

HEADERS

+ END_STREAM

+ END_HEADERS

:method: GET

:scheme: http

:path: /index.html

:authority: example.com

accept: text/html


• Mapping the HTTP Response to Frames

Topline HTTP/2 FeaturesHeader Compression

HTTP response Frames

HTTP/1.1 200 OK

Content-Length: 11

Content-Type: text/html

May The Force Be With You

HEADERS

- END_STREAM

+ END_HEADERS

:status: 200

content-length: 11

content-type: text/html

DATA

+ END_STREAM

May The Force Be With You


Topline HTTP/2 FeaturesHPACK header compression

HTTP Request 1

:method GET

:scheme https

:host example.com

:path /index.html

:authority example.org

:accept text/html

user-agent Mozilla/5.0

HTTP Request 2

:method GET

:scheme https

:host example.com

:path /info.html


:accept text/html


HEADERS frame (Stream 1)

:method GET

:scheme https

:host example.com

:path /index.html


:accept text/html


HEADERS frame (Stream 3)

:path /info.html


• Attach priority information to streams

• Priority located in the header frame or the priority frame

• Only a suggestion to the server

Topline HTTP/2 FeaturesStream Prioritization

B D C

A

2 14 10

B C

A

4 8


• Eliminate the need for resource inlining

• The sever can proactively send resources to the client

• Client can reject PUSH_PROMISE by responding

RST_STREAM

Topline HTTP/2 FeaturesServer Push

Servlet 4.0 Features


Servlet 4.0 FeaturesServer Push

• Most visible improvements in servlets

• Best place to know what resources a request needs


Servlet 4.0 FeaturesPushBuilder


• Browser requests index.html

• Server discovers need for css and js

• Get PushBuilder from HTTP request

• Set path to css and invoke push

• Set path to js and invoke push

• Then responds with index.html

• The PushBuilder can be reused

Servlet 4.0 FeaturesTypical Journey


Servlet 4.0 FeaturesPushBuilder Dive Deeper

• Constructed with request method set to GET by default

• Conditional, range, expectation, authorization and request headers

are removed• Cookies are only added if the maxAge has not expired

• Only required setting is the URI path to the resource• Must be set before every call to push()


• Simple usage

Servlet 4.0 FeaturesServlets and ServerPush


Servlet 4.0 FeaturesFilters and Server Push


• Web framework use case most important

• Dependent on knowing the resources the client requires

• Frameworks best placed to take advantage of server push

• JSF users get server push for free

Servlet 4.0 FeaturesJSF Use Case


• SETTINGS_ENABLE_PUSH clients disable server push

• RST_STREAM rejects cached resources

• Servlet containers must honour request to not receive

Servlet 4.0 FeaturesDisable/Reject Server Push


• Perfectly backward compatible

• Rework to take advantage of Server Push

• Consider removing frontend workarounds

• JSF developers do nothing

Servlet 4.0 FeaturesBackward Compatible

Server Support


• GlassFish 5.0 (nightly)

Reference implementation

• Payara 5.0

Has a branch for Java EE 8 development

• Jetty Stable-9 (9.4.5.v20170502)

org.eclipse.jetty.servlets.PushCacheFilter/PushBuilder

Server ImplementationServlet Support


• WildFly 10 (Undertow)

Initial PushBuilder support implemented in Undertow master

• Tomcat 9.0.0.M20

PushBuilder support in thejavax.servlets.http package

• Netty 4.1

HTTP/2 implementation takes full advantage of headline

features

Server ImplementationServlet Support

Status Update


• As of 23 May 2017 in Public Review ballot status

• Issue Tracker: github.com/javaee/servlet-spec/issues

• JCP Specification: jcp.org/en/jsr/detail?id=369

• Twitter: @servlet_spec

Status UpdateJSP 369: Servlet Specification

https://github.com/javaee/servlet-spec/issues

Extra Bits


• The goal of HTTP/2 is to improve performance

• Cloudflare HTTP/2 demonstration tool

www.cloudflare.com/http2

• Anthum's HTTP vs HTTPS

www.httpvshttps.com

Performance TestsShow me the performance

http://www.cloudflare.com/http2

http://www.httpvshttps.com/


• Daniel Stenberg book: bagder.gitbooks.io/http2-explained

• Free O’Reilly e-book:

www.oreilly.com/webops-perf/free/HTTP2-high-perf-

browser-networking.csp

• FAQ: http2.github.io/faq

Useful Resources

bagder.gitbooks.io/http2-explained

http://www.oreilly.com/webops-perf/free/HTTP2-high-perf-browser-networking.csp

http2.github.io/faq


Q & A

Alex Theedom @readlearncode

Java EE 8:

What Servlet 4.0 and

HTTP/2 mean?

jdkio: java ee 8 what servlet 4 and http2 mean to you

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