Webmachine a practical executable model for HTTP Justin Sheehy - - PowerPoint PPT Presentation

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Webmachine a practical executable model for HTTP Justin Sheehy - - PowerPoint PPT Presentation

Dec 26, 2022 282 likes •661 views

Webmachine a practical executable model for HTTP Justin Sheehy justin@basho.com Webmachine a practical executable model for HTTP a toolkit for HTTP-based systems Webmachine a practical executable model for HTTP a toolkit for easily

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Webmachine

a practical executable model for HTTP

Justin Sheehy

justin@basho.com

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Webmachine

a practical executable model for HTTP

HTTP-based systems a toolkit for

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Webmachine

HTTP-based systems well-behaved easily creating a toolkit for

a practical executable model for HTTP

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Webmachine

HTTP-based systems well-behaved easily creating? a toolkit for

a practical executable model for HTTP

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Webmachine

HTTP-based systems well-behaved? easily creating a toolkit for

a practical executable model for HTTP

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HTTP is complicated.

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Webmachine makes HTTP easier.

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  • module(twohundred_resource).
  • export([init/1, to_html/2]).
  • include_lib("webmachine/include/webmachine.hrl").

init([]) -> {ok, undefined}. to_html(ReqData, State) -> {"Hello, Webmachine world", ReqData, State}.

(that’s it!)

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Want to get more interesting?

Just add generate_etag or last_modified...

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...and now you have conditional requests.

generate_etag(RD, State) -> {mochihex:to_hex(erlang:phash2(State)), RD, State}. last_modified(RD, State) -> {filelib:last_modified(State#s.fpath), RD, State}.

Just add generate_etag or last_modified...

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A resource family is just a set of functions.

to_html(ReqData,State) -> {Body,ReqData,State}. generate_etag(ReqData,State) -> {ETag,ReqData,State}. last_modified(ReqData,State) -> {Time,ReqData,State}. resource_exists(ReqData,State) -> {bool,ReqData,State}. is_authorized(ReqData,State) -> {bool,ReqData,State}. ... f(ReqData,State) -> {RetV,ReqData,State}.

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A resource family is just a set of functions.

f(ReqData,State) -> {RetV,ReqData,State}.

Resource functions are referentially transparent and have a uniform interface.

function behavior request/ response data process state + +

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Manipulating Request/Response Data

f(ReqData,State) -> {RetV,ReqData,State}.

The wrq module accesses and (nondestructively) modifies ReqData.

wrq:get_req_header(HdrName,ReqData) -> 'undefined' | HdrVal wrq:get_qs_value(Key,Default,ReqData) -> Value wrq:set_resp_header(HdrName,HdrVal,ReqData) -> NewReqData

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URL Dispatching = Pattern Matching

{["a"],some_resource,[]} pattern resource family args

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URL Dispatching = Pattern Matching

{["a"],some_resource,[]} http://myhost/a match! any other URL no match If no patterns match, then 404 Not Found. /a

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URL Dispatching = Pattern Matching

{["a"],some_resource,[]} /a wrq:disp_path wrq:path wrq:path_info wrq:path_tokens [] "/a" [] [] {["a" ,some_resource,[]}

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URL Dispatching = Pattern Matching

{["a", '*'],some_resource,[]} /a wrq:disp_path wrq:path wrq:path_info wrq:path_tokens [] "/a" [] [] (binds the remaining path) ,some_resource,[]} {["a"

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URL Dispatching = Pattern Matching

{["a", '*'],some_resource,[]} /a wrq:disp_path wrq:path wrq:path_info wrq:path_tokens “b/c” "/a/b/c" [] [“b”, “c”] /a/b/c {["a", ],some_resource,[]}

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URL Dispatching = Pattern Matching

{["a", foo],some_resource,[]} /a wrq:disp_path wrq:path wrq:path_info wrq:path_tokens “b/c” "/a/b/c" [] [“b”, “c”] /a/b/c (name-binds a path segment) 404 {["a", ],some_resource,[]}

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URL Dispatching = Pattern Matching

{["a", foo],some_resource,[]} /a wrq:disp_path wrq:path wrq:path_info wrq:path_tokens [] "/a/b" [{foo, “b”}] [] /a/b {["a", foo some_resource,[]}

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URL Dispatching = Pattern Matching

{["a", foo, '*'],some_resource,[]} wrq:disp_path wrq:path wrq:path_info wrq:path_tokens [] "/a/b" [{foo, “b”}] [] /a/b {["a", foo some_resource,[]}

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URL Dispatching = Pattern Matching

{["a", foo, '*'],some_resource,[]} wrq:disp_path wrq:path wrq:path_info wrq:path_tokens “c/d” "/a/b/c/d" [{foo, “b”}] [“c”,”d”] /a/b/c/d /a/b

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URL Dispatching = Pattern Matching

{["a", foo, '*'],some_resource,[]} wrq:disp_path wrq:path wrq:path_info wrq:path_tokens “c/d” "/a/b/c/d" [{foo, “b”}] [“c”,”d”] /a/b/c/d query strings are easy too /a/b/c/d?fee=ah&fie=ha wrq:get_qs_value("fie",ReqData) -> “ha”

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The Webmachine Visual Debugger

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Hooray!

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But sometimes things don’t go as well.

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It’s nice to know where your errors are.

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wrq:path(RD) -> "/d/test?q=1.5" {{error,{error,badarg, [{erlang,list_to_integer,["1.5"]}, {some_resource,resource_exists,2}...

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malformed_request(ReqData, State) -> {case catch list_to_integer(wrq:get_qs_value("q","0",ReqData)) of {'EXIT', _} -> true; _ -> false end, ReqData, State}.

  • export([malformed_request/2]).
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Visual debugging helps you put the fixes in the right place.

400 Bad Request

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Webmachine is a higher-level abstraction for HTTP .

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Webmachine is not a “framework.”

No built-in templating, no ORM or built-in storage. Webmachine is a good component in a framework.

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Webmachine is not an all-purpose network server.

No support for arbitrary sockets, etc. Webmachine is shaped like HTTP .

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Webmachine is

A toolkit for easily creating well-behaved HTTP systems.

a resource server for the Web.

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Webmachine is sincerely flattered.

dj-webmachine: clothesline: lemmachine: Django/Python Clojure Agda

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Webmachine

a practical executable model for HTTP http://webmachine.basho.com/

Justin Sheehy

justin@basho.com