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Learning HTTP at ConFoo

Learning HTTP at ConFoo

HTTP is the fabric of the web and the growing API economy. Whether you’re building a backend or a frontend application, creating an API, or consuming an API, it’s helpful to understand the basics of HTTP. Topics covered will include HTTP methods, request headers, request URIs, response status codes, response headers, resource representations, authentication, content negotiation, and caching.

Bradley Holt

February 26, 2016
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  1. The World Wide Web HTTP (Hypertext Transfer Protocol) was originally

    invented to serve HTML (Hypertext Markup Language) Web pages @BradleyHolt
  2. GET /index.html HTTP/1.0 GET an HTML Page @BradleyHolt HTTP/1.0 200

    OK
 
 <html>
 <body>
 <h1>I'm a Web Page!</h1>
 </body>
 </html>
  3. Mobile Apps Most mobile apps use one or more mobile

    backend APIs, many of which are HTTP APIs
  4. Distributed Systems Understanding HTTP can help you understand distributed systems;

    the web is the largest distributed system ever created
  5. Apache CouchDB CouchDB is a document database featuring an HTTP

    API, JSON documents, and peer-to-peer replication @BradleyHolt
  6. CouchDB 2.0 Developer Preview $ git clone https://git-wip-us.apache.org/repos/asf/couchdb.git! $ npm

    install -g grunt-cli! $ cd couchdb! $ git checkout developer-preview-2.0! $ ./configure! $ make! $ dev/run! [ * ] Developers cluster is set up at http://127.0.0.1:15984.! Admin username: root! Password: +2/y7v6h @BradleyHolt http://couchdb.apache.org/developer-preview/2.0/
  7. http-console $ npm install http-console -g! $ http-console 127.0.0.1:15984! >

    http-console 0.6.3! > Welcome, enter .help if you're lost.! > Connecting to 127.0.0.1 on port 15984.! @BradleyHolt https://github.com/cloudhead/http-console
  8. http-console http://127.0.0.1:15984/> GET /! HTTP/1.1 200 OK! Content-Type: text/plain; charset=utf-8!

    ! {! couchdb: 'Welcome',! version: '9afa6a0',! vendor: { name: 'The Apache Software Foundation' }! } @BradleyHolt https://github.com/cloudhead/http-console
  9. http-console $ http-console https://bradley-holt.cloudant.com! > http-console 0.6.3! > Welcome, enter

    .help if you're lost.! > Connecting to bradley-holt.cloudant.com on port 443.! @BradleyHolt https://github.com/cloudhead/http-console
  10. http-console https://bradley-holt.cloudant.com:443/> GET /! HTTP/1.1 200 OK! Content-Type: text/plain; charset=utf-8!

    ! {! couchdb: 'Welcome',! version: 'acfd7cb',! vendor: {! name: 'IBM Cloudant',! version: '5253',! variant: 'paas'! },! features: [ 'geo' ]! }! @BradleyHolt https://github.com/cloudhead/http-console
  11. Request Methods A request method indicates the action to be

    performed on a resource @BradleyHolt GET /kittens POST /kittens DELETE /kittens/mittens PUT /kittens/mittens
  12. Resources A resource is identified by a Uniform Resource Identifier

    (URI) @BradleyHolt /kittens /kittens?q=mittens /kittens/mittens /kittens/mittens/photo
  13. Status Codes Every HTTP response includes a numeric status code

    @BradleyHolt 200 OK 304 Not Modified 500 Internal Server Error 409 Conflict
  14. 409 Conflict The request would create a conflict with the

    current state of the resource @BradleyHolt
  15. 500 Internal Server Error The server encountered an internal error

    and was not able to fulfill the request @BradleyHolt
  16. Request Headers A client can provide additional details about a

    request with request headers @BradleyHolt GET /kittens
 Accept: application/json POST /kittens
 Accept: application/json
 Content-Type: application/json
 
 {
 …
 } DELETE /kittens/mittens
 Accept: application/json PUT /kittens/mittens
 Accept: application/json
 Content-Type: application/json
 
 {
 …
 }
  17. Response Headers A server can provide additional details about a

    response with response headers @BradleyHolt 200 OK
 Content-Type: application/json
 Etag: "e146018c82000fdc"
 
 {
 …
 } 201 Created
 Content-Type: application/json
 Location: /kittens
 
 {
 …
 } 500 Internal Server Error
 Content-Type: application/json
 
 {
 …
 } 409 Conflict
 Content-Type: application/json
 
 {
 …
 }
  18. Example Request and Response An example of an HTTP client

    request and an HTTP server response @BradleyHolt HTTP/1.1 200 OK
 Content-Type: application/json
 Etag: "e146018c82000fdc"
 
 {
 …
 } GET /kittens HTTP/1.1
 Accept: application/json
  19. Content Negotiation Allows for different representations of a resource to

    be served from the same URI @BradleyHolt HTTP/1.1 200 OK
 Content-Type: image/gif
 Etag: "52CAA3A43D34531E"
 
 R0lGODlhAQABAIAAAP/// wAAACwAAAAAAQABAAACAkQBADs= GET /kittens/mittens/photo HTTP/1.1
 Accept: image/gif
  20. Content Negotiation Allows for different representations of a resource to

    be served from the same URI @BradleyHolt HTTP/1.1 200 OK
 Content-Type: image/png
 Etag: "2EB93EA080ECAA64"
 
 iVBORw0KGgoAAAANSUhEUgAAAAEAAA ABCAAAAAA6fptVAAAACklEQVQYV2P4 DwABAQEAWk1v8QAAAABJRU5ErkJggg == GET /kittens/mittens/photo HTTP/1.1
 Accept: image/png
  21. Connecting to CouchDB 2.0 $ http-console root:+2/[email protected]:15984 --json! > http-console

    0.6.3! > Welcome, enter .help if you're lost.! > Connecting to 127.0.0.1 on port 15984.! @BradleyHolt
  22. Connecting to IBM Cloudant $ http-console https://bradley-holt:[email protected] --json! > http-console

    0.6.3! > Welcome, enter .help if you're lost.! > Connecting to bradley-holt.cloudant.com on port 443.! @BradleyHolt
  23. PUT a Database /> PUT /kittens! ... ! HTTP/1.1 201

    Created! Content-Type: application/json! Location: http://127.0.0.1/kittens! ! { ok: true }! @BradleyHolt
  24. PUT a Database Again /> PUT /kittens! ... ! HTTP/1.1

    412 Precondition Failed! Content-Type: application/json! ! { error: 'file_exists', reason: 'The database could not be created, the file already exists.' }! @BradleyHolt
  25. POST a Document /kittens> POST /! ... { "_id": "mittens",

    "age_weeks": 10, "weight_kilograms": 0.997 }! @BradleyHolt
  26. POST a Document /kittens> POST /! ... { "_id": "mittens",

    "age_weeks": 10, "weight_kilograms": 0.997 }! HTTP/1.1 201 Created! Content-Type: application/json! Location: http://127.0.0.1/kittens/mittens! ! {! ok: true,! id: 'mittens',! rev: '1-e665a40d9ea9711c983e907f0b0b6e8a'! }! @BradleyHolt
  27. GET All Documents /kittens> GET /_all_docs! HTTP/1.1 200 OK! Content-Type:

    application/json! Etag: "e1463d2fc36a120a6586018c82000fdc"! ! {! total_rows: 1,! offset: 0,! rows: [! {! id: 'mittens',! key: 'mittens',! value: { rev: '1-e665a40d9ea9711c983e907f0b0b6e8a' }! }! ]! }! @BradleyHolt
  28. GET a Document /kittens> GET /mittens! HTTP/1.1 200 OK! Content-Type:

    application/json! Etag: "1-e665a40d9ea9711c983e907f0b0b6e8a"! ! {! _id: 'mittens',! _rev: '1-e665a40d9ea9711c983e907f0b0b6e8a',! age_weeks: 10,! weight_kilograms: 0.997! }! @BradleyHolt
  29. PUT an Attachment /kittens> .headers! Accept: application/json! Content-Type: application/json! Authorization:

    Basic cm9vdDorMi95N3Y2aA==! Host: 127.0.0.1! /kittens> Content-Type: image/gif! @BradleyHolt
  30. PUT an Attachment /kittens> PUT /mittens/photo?rev=1-e665a40d9ea9711c983e907f0b0b6e8a! ... R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=! HTTP/1.1 201

    Created! Content-Type: application/json! Location: http://127.0.0.1/kittens/mittens/photo! ! {! ok: true,! id: 'mittens',! rev: '2-d858e51453a5785bafe517b7eddc5a98'! }! @BradleyHolt
  31. PUT an Attachment /kittens> PUT /mittens/photo?rev=1-e665a40d9ea9711c983e907f0b0b6e8a! ... R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=! HTTP/1.1 201

    Created! Content-Type: application/json! Location: http://127.0.0.1/kittens/mittens/photo! ! {! ok: true,! id: 'mittens',! rev: '2-d858e51453a5785bafe517b7eddc5a98'! }! /kittens> ! @BradleyHolt
  32. PUT an Attachment /kittens> PUT /mittens/photo?rev=1-e665a40d9ea9711c983e907f0b0b6e8a! ... R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=! HTTP/1.1 201

    Created! Content-Type: application/json! Location: http://127.0.0.1/kittens/mittens/photo! ! {! ok: true,! id: 'mittens',! rev: '2-d858e51453a5785bafe517b7eddc5a98'! }! /kittens> Content-Type: application/json! @BradleyHolt
  33. GET an Attachment /kittens> GET /mittens/photo! HTTP/1.1 200 OK! Content-Type:

    image/gif! Etag: "UsqjdPnY6ApD2ENFOglFHg=="! ! R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=! @BradleyHolt
  34. DELETE a Document /kittens> DELETE /mittens! HTTP/1.1 409 Conflict! Content-Type:

    application/json! ! { error: 'conflict', reason: 'Document update conflict.' }! @BradleyHolt
  35. DELETE a Document /kittens> HEAD /mittens! HTTP/1.1 200 OK! Etag:

    "2-d858e51453a5785bafe517b7eddc5a98"! ! @BradleyHolt
  36. DELETE a Document /kittens> If-Match: "2-d858e51453a5785bafe517b7eddc5a98"! /kittens> DELETE /mittens! HTTP/1.1

    200 OK! Content-Type: application/json! ! {! ok: true,! id: 'mittens',! rev: '3-d0780627ddff7a7f536fe273100cec41'! }! @BradleyHolt
  37. DELETE a Document /kittens> If-Match: "2-d858e51453a5785bafe517b7eddc5a98"! /kittens> DELETE /mittens! HTTP/1.1

    200 OK! Content-Type: application/json! ! {! ok: true,! id: 'mittens',! rev: '3-d0780627ddff7a7f536fe273100cec41'! }! /kittens> ! @BradleyHolt
  38. DELETE a Document /kittens> If-Match: "2-d858e51453a5785bafe517b7eddc5a98"! /kittens> DELETE /mittens! HTTP/1.1

    200 OK! Content-Type: application/json! ! {! ok: true,! id: 'mittens',! rev: '3-d0780627ddff7a7f536fe273100cec41'! }! /kittens> If-Match:! @BradleyHolt
  39. HTTP/2 §  Same methods (GET, POST, PUT, DELETE, etc.), headers,

    and status codes §  No more need for optimizations that reduce the number of HTTP requests (e.g. inlining, concatenation, and sprites) §  Header compression §  Cache pushing §  Ability for clients to cancel a request §  Better performance for encrypted connections §  Binary protocol @BradleyHolt https://www.mnot.net/blog/2014/01/30/http2_expectations
  40. Image Credits §  Dialing Up Web History by Mike Licht,

    on Flickr <https://flic.kr/p/cacNad> §  Web Hosting Servers by Widjaya Ivan, on Flickr <https://flic.kr/p/8onBSX> §  API calls by Tsahi Levent-Levi, on Flickr <https://flic.kr/p/ef9o5F> §  Instagram and other Social Media Apps by Jason Howie, on Flickr <https://flic.kr/p/d41HES> §  interwoven by Jared Hansen, on Flickr <https://flic.kr/p/7Pe1Vb> §  Envelope by Blake Burkhart, on Flickr <https://flic.kr/p/9Zifc3> §  200 - OK by Tomomi, on Flickr <https://flic.kr/p/aVuVsF> §  201 - Created by Tomomi, on Flickr <https://flic.kr/p/aXWm1Z> §  304 - Not Modified by Tomomi, on Flickr <https://flic.kr/p/aXY3dH> §  409 - Conflict by Tomomi, on Flickr <https://flic.kr/p/aV6jzz> §  500 - Internal Server Error by Tomomi, on Flickr <https://flic.kr/p/aVdo6e> §  Flood by Kai Wegner, on Flickr <https://flic.kr/p/b9HCNT> @BradleyHolt