HTTP and Your Angry Dog

Ross Tuck HTTP And Your Angry Dog April 13th, Whisky
Web

Who Am I?

Ross Tuck

Team Lead at Ibuildings Codemonkey Token Foreigner REST nut

@rosstuck

Today's topic:

HTTP & Dogs

The Agenda

Basics

Client Server Request Response

POST /gists HTTP/1.1 Authorization: Basic xxxxxxxx Host: api.github.com Content-Length: 146
{ "description": "the description for this gist", "public": false, "files": { ... Request

{ "description": "the description for this gist", "public": false, "files": { ... Request 2 Parts

{ "description": "the description for this gist", "public": false, "files": { ... Request The body

<!DOCTYPE html> <html> <head> <meta charset='utf-8'> <title>My application</title> ... Request The body

{ "description": "the description for this gist", "public": false, "files": { ... Request The body

{ "description": "the description for this gist", "public": false, "files": { ... Request The headers

{ "description": "the description for this gist", "public": false, "files": { ... Request The good stuff

{ "description": "the description for this gist", "public": false, "files": { ... Request GET, POST, PUT, DELETE

{ "description": "the description for this gist", "public": false, "files": { ... Request Relative URL HTTP version

{ "description": "the description for this gist", "public": false, "files": { ... Request Key/Value pairs

HTTP/1.1 201 Created Date: Sun, 09 Sep 2012 11:42:41 GMT
Content-Length: 1848 Location: https://api.github.com/gists/a43a0cf58 { "description": "the description for this gist", "comments": 0, "created_at": "2012-09-09T11:42:40Z", ... Response Status code

Status Codes

• 2xx • 3xx • 4xx • 5xx OK! Over
there! Client screwed up! Server screwed up!

Content Negotiation

GET /dogs/corgi HTTP/1.1 Host: api.example.com Request

HTTP/1.1 200 OK Date: Sun, 26 Aug 2012 18:00:43 GMT
{ "cute": true, "big": false, "data_dog": true } Response

<dog breed="corgi"> <cute>true</cute> <data capacity="on" /> </dog> Response

GET /dogs/corgi.json HTTP/1.1 Host: api.example.com Request

/dogs/corgi.json !== /dogs/corgi.xml

Imagine the URL as your primary key.

GET /dogs/corgi?_format=json HTTP/1.1 Host: api.example.com Request

POST /dogs/corgi?_format=json HTTP/1.1 Host: api.example.com Request

GET /dogs/corgi HTTP/1.1 Host: api.example.com Accept: application/json Request

More POWAH

GET /dogs/corgi HTTP/1.1 Host: api.example.com Accept: application/json Request

GET /dogs/corgi HTTP/1.1 Host: api.example.com Accept: application/json, application/xml Request How
do I choose?

GET /dogs/corgi HTTP/1.1 Host: api.example.com Accept: application/json, application/xml Request

Content-Type: application/json { "cute": true, "big": false, "data_dog": true } Response

Nifty.

GET /dogs/corgi HTTP/1.1 Host: api.example.com Accept: application/json, application/xml Request

text/html, text/plain

text/html;key=value, text/plain

text/html;key=value;foo=bar, text/plain

text/html, text/plain

text/html, text/plain;q=0.5 Quality (Default 1.0)

text/html, text/plain;q=0.5, text/*;q=0.1 Wildcards

text/html, text/plain;q=0.5, */*;q=0.1 Anything at all

Accept Headers Little weird...

But not so scary.

text/html,application/xhtml+xml, application/xml;q=0.9,*/*;q=0.8

Cool...

What the heck is it good for?

Accept is a “Pattern”

Accept-Language Accept-Encoding Accept-Charset Accept-Ranges

Content-Language Content-Encoding (works differently) Content-Range

Resource vs Representation /dog/corgi JSON, Dutch, Gzipped, /dog/corgi

Resource vs Representation

Best way to version your API. Arguably. Right now.

/v1/dogs/corgi

Accept: application/vnd.dogipedia-v1+json

Accept: application/vnd.dogipedia-v2+json

Client Server GET /dogs/corgi HTTP/1.1 Host: api.example.com

Client Server Proxy GET /dogs/corgi HTTP/1.1 Host: api.example.com

Client Server Proxy GET /dogs/corgi HTTP/1.1 Host: api.example.com Accept: application/json,
text/plain User-Species: cat

Same URL. Different output. WTF should I return?

Client Server Proxy GET /dogs/corgi HTTP/1.1 Host: api.example.com Accept: application/json,
text/plain User-Species: cat

Client Server Proxy

Here's how. Hint: Involves the Vary header!

Client Server Proxy /dogs/corgi Accept: application/json, text/plain User-Species: cat

Content-Type: application/json Vary: Accept {“json”: “omgz”} Response

Client Server Proxy URL and Accept? Okay, I got this.

Some time later...

Client Server Proxy /dogs/corgi Accept: application/json, text/plain User-Species: aardvark

Client Server Proxy Valid cache. I has it.

Client Server Proxy ZZ Z Z Z Z

Content-Type: application/json Vary: Accept {“json”: “omgz”} Response

Content-Type: application/json Vary: Accept, User-Species {“json”: “omgz”} Response

Content-Type: application/json Vary: Accept, User-Species {“json”: “dogs rule, cats drool”} Response

Request headers. Not Response!

Bad Reputation? 2 Reasons

1. Accept-Encoding -Language

2. Internet Explorer

Caching

Expires Pragma Cache-Control

Expires Cache-Control HTTP 1.0 HTTP 1.1

HTTP/1.1 200 OK Expires: Thu, 07 Feb 2013 22:00:00 GMT
{“herp”: “derp”} Response

HTTP/1.1 200 OK Cache-Control: max-age=120 {“herp”: “derp”} Response

HTTP/1.1 200 OK Cache-Control: max-age=120 Response

Expires Cache-Control HTTP 1.0 HTTP 1.1

HTTP/1.1 200 OK Cache-Control: max-age=120 {“herp”: “derp”} Response

HTTP/1.1 200 OK Cache-Control: max-age=120, s-maxage=120 {“herp”: “derp”} Response Dude,
Where's my dash?

public private no-store no-cache no-transform must-revalidate proxy-revalidate

Mark Nottingham's Caching Tutorial http://www.mnot.net/cache_docs/ Much better than me.

Conditional Requests

The Part About ETags

Conditional Requests

DELETE /ross/reputation HTTP/1.1 Host: api.joind.in If-Talk-Quality: Crap Request

if ($talkQuality === 'Crap') { delete($rossReputation); } Not real code
Server

What kind of conditions?

If-Match If-None-Match If-Modified-Since If-Unmodified-Since If-Range ETags Datetimes Either

Wait a second, Ross. Audience

What the heck is an ETag, anyways?

A string. Any string.

One rule:

Represent the current state.

“14” “a381bedb5d4478053eb04be35f8798dd” “winnie-the-pooh”

...for the current representation.

etag(“v14-json-en”) !== etag(“v14-xml-en”) Don't cross the streams Server

Last Modified Date sounds easier... Audience

Wed, 15 Nov 1995 04:58:08 GMT One second of precision

Caching With Conditionals

Use Case

GET /gists/3481910 HTTP/1.1 Host: api.github.com Accept: */* Request

HTTP/1.1 200 OK Server: nginx/1.0.13 Date: Sun, 26 Aug 2012
18:00:43 GMT Vary: Accept ETag: "f4e15911542b92b44bb38186e71cc8f5" "history": [ { "version": "529f6311d5518977534b6e1fd313...", ... Response

... "user": { "gravatar_id": "c26bfcbd5f786591e036fa0", "avatar_url": "https://secure.gravatar...", "login": "rosstuck", "url":
"https://api.github.com/users/rosstuck", "id": 146766 }, "change_status": { "additions": 1, "deletions": 0, "total": 1 }, Response

"url": "https://api.github.com/gists/348...", "committed_at": "2012-08-26T17:40:03Z" } ], "git_pull_url": "git://gist.github.com/34819...", "forks": [
], "html_url": "https://gist.github.com/3481910", "git_push_url": "[email protected]:3481910.git", "comments": 0, "user": { Response

18:00:43 GMT Vary: Accept ETag: "f4e15911542b92b44bb38186e71cc8f5" { "history": [ { "version": "529f6311d5518970903cb5427534b6e1fd313aca", "user": { "gravatar_id": "c26bfcbd5f786591e036fa0958a11e8b", "avatar_url": "https://secure.gravatar.com/avatar/c26bfcbd5f786591e036fa0958a11e8b?d=https://a2... "login": "rosstuck", "url": "https://api.github.com/users/rosstuck", "id": 146766 }, "change_status": { "additions": 1, "deletions": 0, "total": 1 }, "url": "https://api.github.com/gists/3481910/529f6311d5518970903cb5427534b6e1fd313aca", "committed_at": "2012-08-26T17:40:03Z" } ], "git_pull_url": "git://gist.github.com/3481910.git", Response "forks": [ ], "html_url": "https://gist.github.com/3481910", "git_push_url": "[email protected]:3481910.git", "comments": 0, "user": { "gravatar_id": "c26bfcbd5f786591e036fa0958a11e8b", "avatar_url": "https://secure.gravatar.com/avatar/c26bfcbd5f78659....",} "login": "rosstuck", "url": "https://api.github.com/users/rosstuck", "id": 146766 }, "public": true, "created_at": "2012-08-26T17:40:03Z", "files": { "gistfile1.txt": { "type": "text/plain", "filename": "gistfile1.txt", "raw_url": "https://gist.github.com/raw/3481910/8b6946739e8098408ee3af96... "content": "Hello PFC!", "language": null, "size": 10 } }, "description": "", "url": "https://api.github.com/gists/3481910", "updated_at": "2012-08-26T17:40:03Z", "id": "3481910" }

GET /gists/3481910 HTTP/1.1 Host: api.github.com Accept: */* If-None-Match: "f4e15911542b92b44bb38186e71cc8f5" Request

HTTP/1.1 304 Not Modified Server: nginx/1.0.13 Date: Sun, 26 Aug
2012 18:00:43 GMT Vary: Accept ETag: "f4e15911542b92b44bb38186e71cc8f5" Response

HTTP/1.1 304 Not Modified Server: nginx/1.0.13 Date: Sun, 26 Aug
2012 18:00:43 GMT Vary: Accept ETag: "f4e15911542b92b44bb38186e71cc8f5" Response No giant body!

Caching. You has it.

GET /gists/3481910 HTTP/1.1 Host: api.github.com Accept: */* If-None-Match: "a381bedb5d4478053eb04be35f8798dd" Request

GET /gists/3481910 HTTP/1.1 Host: api.github.com Accept: */* If-None-Match: "ross-is-a-poo-poo-head" Request

18:00:43 GMT Vary: Accept ETag: "f4e15911542b92b44bb38186e71cc8f5" "history": [ { "version": "529f6311d5518977534b6e1fd313...", Response

No ETag Old ETag Matching ETag Full Body Full Body
No Body → → →

...on supported servers.

Parsing Bandwidth Response time Probably ...Maybe

However...

“The fastest request is one you don't make.” - Jesus

More Fun With ETags

Optimistic Concurrency Control “Record Versioning”

Request

GET /gists/3481910 HTTP/1.1 Host: api.github.com Accept: */* If-None-Match: "f4e15911542b92b44bb38186e71cc8f5" Request

PATCH /gists/3481910 HTTP/1.1 Host: api.github.com Accept: */* If-None-Match: "f4e15911542b92b44bb38186e71cc8f5" Request

PATCH /gists/3481910 HTTP/1.1 Host: api.github.com Accept: */* If-Match: "f4e15911542b92b44bb38186e71cc8f5" Request

PATCH /gists/3481910 HTTP/1.1 Host: api.github.com Accept: */* If-Match: "f4e15911542b92b44bb38186e71cc8f5" {
"description": "cheese om nom nom" } Request

Response

Response HTTP/1.1 200 OK Server: nginx/1.0.13 Date: Sat, 01 Sep
2012 14:01:38 GMT ETag: "899b76047a5e68445668374c2e0faa32" { "description": "cheese om nom nom", "user": { "login": "rosstuck", ...

It works.

So what?

What if I send something...

PATCH /gists/3481910 HTTP/1.1 Host: api.github.com Accept: */* If-Match: "899b76047a5e68445668374c2e0faa32" {

PATCH /gists/3481910 HTTP/1.1 Host: api.github.com Accept: */* If-Match: "stay-puft-marshmellow-dog!" {

HTTP/1.1 412 Precondition Failed Server: nginx/1.0.13 Date: Sun, 26 Aug
2012 18:00:43 GMT Response

Response

if (“stay-puft-marshmellow-dog” == “f4e1591..”) { patchTheRecord(); } Server

if (“stay-puft-marshmellow-dog” == “f4e1591..”) { patchTheRecord(); } else { sendScary412Message();
} Server

Your ETag is out of date.

“Two guys on the same record” problem

Other Scary Precondition Errors

Disclaimer New Stuff Ahead

DELETE /gists/3481910 HTTP/1.1 Host: api.github.com Request

HTTP/1.1 428 Precondition Required Server: nginx/1.0.13 Date: Sun, 26 Aug

Am I operating on the latest version?

DELETE /gists/3481910 HTTP/1.1 Host: api.github.com Request

DELETE /gists/3481910 HTTP/1.1 Host: api.github.com If-Match: "f4e15911542b92b44bb38186e71cc8f5" Request

HTTP/1.1 204 No Content Server: nginx/1.0.13 Date: Sun, 26 Aug

Look before you leap.

Tooling

Epilogue: HTTP & Dogs

Content Negotiation Vary Caching Preconditions

Treat it like your framework.

HTTP and Your Angry Dog

HTTP and Your Angry Dog

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