What Servlet 4 and HTTP/2 mean to you

Alex Theedom @alextheedom

Alex Theedom, Senior Java Developeralextheedom.com

@alextheedom

Who am I?

What’s on?1 Why Do We Need HTTP/22 Work-Arounds to HTTP1.13 HTTP Sockets4 Topline HTTP/2 Features5 Servlet 4.0 Features6 Server Support7 What about SPDY?8 HTTP/2 Performance9 Tracking HTTP/2 Adoption10 Summary and Q&A

■Increase perceived performance of web

■HTTP protocol not suitable

■Since 2011 average web page size increased by over 300%

■The problem with HTTP/1.1

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

300%Source: HTTPArchive.com

■Requests resources in parallel HTTP 1■One request per TCP connection■HTTP1.1 Pipelining: multiple requests■Responds in sequence■Delay causes head-of-line blocking

Why Do We Need HTTP/2How a browser loads a webpage?

open

close

client serverno pipelining

index.html

style_1.css

logo.jpg

open

close

client serverpipelining

time

index.html

style_1.csslogo.jpg

Multiple connections

However two issues1. TCP sockets expensive

2. Browser max connections

Work-Arounds to HTTP1.1Solution to Head-Of-Line Blocking

open

close

client server

connection 1style_1.css

open

close

client server

connection 2javaScript_1.js

open

close

client server

connection 3image_1.png

Work-Arounds to HTTP1.1CSS/JavaScript File Concatenation

background.cssheader.cssmenu.cssstyle.css

Work-Arounds to HTTP1.1CSS and JavaScript Inlining

■Embed image in web page■Base 64 encoded

■Time spent decoding■Caching difficult

Work-Arounds to HTTP1.1Inlined Assets

One image file consists of many smaller images

Image sprites from Amazon, Google and Facebook.

Work-Arounds to HTTP1.1Image Sprite Sheet

Work-Arounds to HTTP1.1Domain Sharding

web pagey.example.com

x.example.com

server 2

server 1

logo.jpg

icon.jpg

header.css

menu.css

■Not much specified■Throw away resources

■No maximum open sockets

HTTP SocketsWhat HTTP1.1 Says About Sockets

■Much is specified■Scares resources

■Ideally only open one socket

HTTP SocketsWhat HTTP/2 Says About Sockets

HTTP SocketsAll connections now operate as one connection

open

close

client server

open

close

client server

open

close

client server

open

close

client server open

close

client serveropen

close

client server

■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

■Features:■Request/Response Multiplexing

■Binary Framing ■Header Compression■Stream Prioritization

■Server Push■Upgrade From HTTP1.1

Topline HTTP/2 Features What’s new

■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■Communication broken down into frames

■Frames facilitate interweaving the logical stream

Topline HTTP/2 FeaturesRequest/Response Multiplexing

Hierarchical structure of logical communication blocks

Topline HTTP/2 FeaturesRequest/Response Multiplexing

connectionstream

frame frame frameframe frame frame

message

stream

frame frame frameframe frame frame

messageframe frame frameframe frame frame

message

stream

frame frame frameframe frame frame

messageframe frame frameframe frame frame

messageframe frame frameframe frame frame

message

■Request/Response Multiplexing■Interweave the logical stream over a single TCP

Stream 3 sends header then body and server responds with stream 2 before it receives completed stream 3

Topline HTTP/2 FeaturesRequest/Response Multiplexing

STREAM 1HEADERS

STREAM 3DATA

STREAM 1DATA

STREAM 2HEADERS

STREAM 3HEADERS

STREAM 2DATA

browser

server

■Decomposition of the frame■The frame has a header and the head consists of some information

■Type fields can be■HEADER corresponds to the HTTP headers

■DATA corresponds to the HTTP request body■PRIORITY specifies stream priority

■PUSH_PROMISE notifies of server push intent ■RST_STREAM notifying error, client rejects push

■SETTING, PING, GOAWAY, WINDOW_UPDATE, CONTINUATION

Topline HTTP/2 FeaturesBinary Framing

LENGTH (24)TYPE (8) FLAGS (8)

R STREAM IDENTIFIER (31)FRAME PAYLOADS (0.. n)

Mapping the HTTP Request to Frames

Topline HTTP/2 FeaturesHeader Compression

HTTP request Header FrameGET /index.html HTTP/1.1Host: example.comAccept: 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 Header FrameHTTP/1.1 200 OKContent-Length: 11Content-Type: text/htmlMay The Force Be With You

HEADERS - END_STREAM + END_HEADERS :status: 200 content-length: 11 content-type: text/htmlData FrameDATA + END_STREAMMay The Force Be With You

■Reduces header duplication■scheme, accept, user-agent

■Server and client maintains a table of headers

■Send only difference and references header number

Topline HTTP/2 FeaturesHPACK header compression

HTTP Request 1:method GET:scheme https:host example.com:path /index.html:authority example.org:accept text/htmluser-agent Mozilla/5.0

HTTP Request 2:method GET:scheme https:host example.com:path /info.html:authority example.org:accept text/htmluser-agent Mozilla/5.0

HEADERS frame (Stream 1):method GET:scheme https:host example.com:path /index.html:authority example.org:accept text/htmluser-agent Mozilla/5.0

HEADERS frame (Stream 3):path /info.html

■Attach priority information to streams■Priority can be entered 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

■How do we talk in HTTP/2?

■Two ways to talk in HTTP2■HTTP 1.1 in clear text send upgrade header to upgrade to protocol

h2c■HTTPS use ALPN (TLS extension) and communication continues in

h2

■However Firefox or Chrome does not support h2c

■HTTPS all the way

Topline HTTP/2 FeaturesUpgrade Negotiation

■Servlet API well positioned to enable HTTP2 optimisation

■Servlet 4.0 Appropriate Abstraction

■Provide high level abstraction■Don’t want to program frames at the servlet layer

■OUT: one request = one response■IN: one request = multiple responses

Servlet 4.0 FeaturesAppropriate Abstraction

Servlet 4.0 FeaturesServer Push

■Most visible improvements in servlets

■Improve perceivable performance

■Best place to know what resources a request needs■logo image, stylesheet, menu javascript etc

■Not a replacement for websockets

■JSF will make good use of Server Push and other frameworks

■Implemented as PushBuilder API

Servlet 4.0 FeaturesTypical Journey

1. Browser requests index.html2. Server discovers need for css and js3. Get PushBuilder from HTTP request4. Set path to css and invoke push5. Set path to js and invoke push6. Then responds with index.html

Note7. The pushBuilder can be reused8. index.html returned after pushed resources

RST_STREAM rejects cached resources

■javax.servlet.http.PushBuilder■To use server push, obtain a reference to a PushBuilder from an

HttpServletRequest, mutate the builder as desired, then call push()

Servlet 4.0 FeaturesPushBuilder

Servlet 4.0 FeaturesPushBuilder

■javax.servlet.http.PushBuilder■constructed with request method set to GET■conditional, range, expectation, authorization and request headers

are removed■cookies are only added if the maxAge has not expired■request header set to the request URL plus any query string present■only required setting is the URI path to the resource■must be set before every call to push()

Servlet 4.0 FeaturesServlets and ServerPush

■Simple usage

Servlet 4.0 FeaturesFilters and Server Push

Servlet 4.0 FeaturesJSF Use Case

■Framework use case most important■Dependent on knowing the resources the client requires■Server side web frameworks best placed to take advantage of server

push

Servlet 4.0 FeaturesJava 9 Support

■JEP 110■Does not reinvent HttpClient■Supports HTTP1.1 and HTTP/2

■Full server push support■Two modes: blocking and non-blocking

HttpClient.Builder HttpClient HttpRequest.BuilderHttpRequest: POSTHttpRequest: GET

Servlet 4.0 FeaturesJava 9 Support

■GET

Servlet 4.0 FeaturesJava 9 Support

■POST

Servlet 4.0 FeaturesDisable/Reject Server Push

■Clients can explicitly disabled server push by sending a SETTINGS_ENABLE_PUSH 

■Servlet containers must honor a client’s request to not receive a pushed response

■Browser already has the resource in its cache.■RST_STREAM rejects cached resources

Server ImplementationServlet Support

■GlassFish 5.0 ■Reference implementation

■Payara 5.0■Recently created a branch for Java EE 8 development

■Jetty Stable-9 (9.3.8.v20160314)■org.eclipse.jetty.servlets.PushCacheFilter/PushBuilder

■WildFly 10 (Undertow)■Initial PushBuilder support implemented in Undertow master

■Tomcat 9.0.0.M4 alpha■Initial PushBuilder Supports Servlets 4.0's PushBuilder in the

javax.servlets.http package■Netty 4.1

■HTTP/2 implementation takes full advantage of headline features

Server ImplementationTomcat Configuration

■TLS required■TLS virtual hosting and multiple certificate are supported for a single

connector each virtual host is able to support multiple certificates

What About SPDY?Stepping Stone to HTTP/2

■Primary focus reduce web page load time■Same as HTTP/2■Formed first draft of HTTP/2■Stepping stone to HTTP/2■Chrome will drop support in favour of HTTP/2

HTTP/2 PerformanceOverriding Goal to Improve Performance

■The goal of HTTP/2 is to improve performance

■Cloudflare HTTP/2 demonstration tool cloudflare.com/http2

■Anthum's HTTP vs HTTPS httpvshttps.com 

Tracking HTTP/2 AdoptionHow to Track Adoption

■Servers advise HTTP/2 support during the SSL handshake■Using shodan.io searches can be made using the ssl.alpn filter

Tracking HTTP/2 AdoptionAdoption Data

■Analysis■Between December 2015 and April 2016 HTTP/2 adoption up to 10%■However growth comes from upgrading incumbent version HTTP/2■Combining protocols we see no meaningful change

Q & A

What Servlet 4 and HTTP/2 mean to you

Alex Theedom @alextheedom