crul

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An HTTP client, taking inspiration from Ruby’s faraday and Python’s requests

Package API:

Mocking:

crul now integrates with webmockr to mock HTTP requests. Integration with vcr to mock specifically around tests is coming soon.

Installation

CRAN version

install.packages("crul")

Dev version

devtools::install_github("ropensci/crul")
library("crul")

the client

HttpClient is where to start

(x <- HttpClient$new(
  url = "https://httpbin.org",
  opts = list(
    timeout = 1
  ),
  headers = list(
    a = "hello world"
  )
))
#> <crul connection> 
#>   url: https://httpbin.org
#>   curl options: 
#>     timeout: 1
#>   proxies: 
#>   auth: 
#>   headers: 
#>     a: hello world

Makes a R6 class, that has all the bits and bobs you’d expect for doing HTTP requests. When it prints, it gives any defaults you’ve set. As you update the object you can see what’s been set

x$opts
#> $timeout
#> [1] 1
x$headers
#> $a
#> [1] "hello world"

You can also pass in curl options when you make HTTP requests, see below for examples.

do some http

The client object created above has http methods that you can call, and pass paths to, as well as query parameters, body values, and any other curl options.

Here, we’ll do a GET request on the route /get on our base url https://httpbin.org (the full url is then https://httpbin.org/get)

res <- x$get("get")

The response from a http request is another R6 class HttpResponse, which has slots for the outputs of the request, and some functions to deal with the response:

Status code

res$status_code
#> [1] 200

Status information

res$status_http()
#> <Status code: 200>
#>   Message: OK
#>   Explanation: Request fulfilled, document follows

The content

res$content
#>   [1] 7b 0a 20 20 22 61 72 67 73 22 3a 20 7b 7d 2c 20 0a 20 20 22 68 65 61
#>  [24] 64 65 72 73 22 3a 20 7b 0a 20 20 20 20 22 41 22 3a 20 22 68 65 6c 6c
#>  [47] 6f 20 77 6f 72 6c 64 22 2c 20 0a 20 20 20 20 22 41 63 63 65 70 74 22
#>  [70] 3a 20 22 61 70 70 6c 69 63 61 74 69 6f 6e 2f 6a 73 6f 6e 2c 20 74 65
#>  [93] 78 74 2f 78 6d 6c 2c 20 61 70 70 6c 69 63 61 74 69 6f 6e 2f 78 6d 6c
#> [116] 2c 20 2a 2f 2a 22 2c 20 0a 20 20 20 20 22 41 63 63 65 70 74 2d 45 6e
#> [139] 63 6f 64 69 6e 67 22 3a 20 22 67 7a 69 70 2c 20 64 65 66 6c 61 74 65
#> [162] 22 2c 20 0a 20 20 20 20 22 43 6f 6e 6e 65 63 74 69 6f 6e 22 3a 20 22
#> [185] 63 6c 6f 73 65 22 2c 20 0a 20 20 20 20 22 48 6f 73 74 22 3a 20 22 68
#> [208] 74 74 70 62 69 6e 2e 6f 72 67 22 2c 20 0a 20 20 20 20 22 55 73 65 72
#> [231] 2d 41 67 65 6e 74 22 3a 20 22 6c 69 62 63 75 72 6c 2f 37 2e 35 34 2e
#> [254] 30 20 72 2d 63 75 72 6c 2f 33 2e 31 20 63 72 75 6c 2f 30 2e 35 2e 32
#> [277] 22 0a 20 20 7d 2c 20 0a 20 20 22 6f 72 69 67 69 6e 22 3a 20 22 31 33
#> [300] 36 2e 31 35 32 2e 32 30 39 2e 34 34 22 2c 20 0a 20 20 22 75 72 6c 22
#> [323] 3a 20 22 68 74 74 70 73 3a 2f 2f 68 74 74 70 62 69 6e 2e 6f 72 67 2f
#> [346] 67 65 74 22 0a 7d 0a

HTTP method

res$method
#> [1] "get"

Request headers

res$request_headers
#> $`User-Agent`
#> [1] "libcurl/7.54.0 r-curl/3.1 crul/0.5.2"
#> 
#> $`Accept-Encoding`
#> [1] "gzip, deflate"
#> 
#> $Accept
#> [1] "application/json, text/xml, application/xml, */*"
#> 
#> $a
#> [1] "hello world"

Response headers

res$response_headers
#> $status
#> [1] "HTTP/1.1 200 OK"
#> 
#> $connection
#> [1] "keep-alive"
#> 
#> $server
#> [1] "meinheld/0.6.1"
#> 
#> $date
#> [1] "Sat, 24 Feb 2018 03:15:04 GMT"
#> 
#> $`content-type`
#> [1] "application/json"
#> 
#> $`access-control-allow-origin`
#> [1] "*"
#> 
#> $`access-control-allow-credentials`
#> [1] "true"
#> 
#> $`x-powered-by`
#> [1] "Flask"
#> 
#> $`x-processed-time`
#> [1] "0"
#> 
#> $`content-length`
#> [1] "352"
#> 
#> $via
#> [1] "1.1 vegur"

And you can parse the content with parse()

res$parse()
#> No encoding supplied: defaulting to UTF-8.
#> [1] "{\n  \"args\": {}, \n  \"headers\": {\n    \"A\": \"hello world\", \n    \"Accept\": \"application/json, text/xml, application/xml, */*\", \n    \"Accept-Encoding\": \"gzip, deflate\", \n    \"Connection\": \"close\", \n    \"Host\": \"httpbin.org\", \n    \"User-Agent\": \"libcurl/7.54.0 r-curl/3.1 crul/0.5.2\"\n  }, \n  \"origin\": \"136.152.209.44\", \n  \"url\": \"https://httpbin.org/get\"\n}\n"
jsonlite::fromJSON(res$parse())
#> No encoding supplied: defaulting to UTF-8.
#> $args
#> named list()
#> 
#> $headers
#> $headers$A
#> [1] "hello world"
#> 
#> $headers$Accept
#> [1] "application/json, text/xml, application/xml, */*"
#> 
#> $headers$`Accept-Encoding`
#> [1] "gzip, deflate"
#> 
#> $headers$Connection
#> [1] "close"
#> 
#> $headers$Host
#> [1] "httpbin.org"
#> 
#> $headers$`User-Agent`
#> [1] "libcurl/7.54.0 r-curl/3.1 crul/0.5.2"
#> 
#> 
#> $origin
#> [1] "136.152.209.44"
#> 
#> $url
#> [1] "https://httpbin.org/get"

curl options

res <- HttpClient$new(url = "http://api.gbif.org/v1/occurrence/search")
res$get(query = list(limit = 100), timeout_ms = 100)
#> Error in curl::curl_fetch_memory(x$url$url, handle = x$url$handle) :
#>   Timeout was reached

Asynchronous requests

The simpler interface allows many requests (many URLs), but they all get the same options/headers, etc. and you have to use the same HTTP method on all of them:

(cc <- Async$new(
  urls = c(
    'https://httpbin.org/',
    'https://httpbin.org/get?a=5',
    'https://httpbin.org/get?foo=bar'
  )
))
res <- cc$get()
lapply(res, function(z) z$parse("UTF-8"))

The AsyncVaried interface accepts any number of HttpRequest objects, which can define any type of HTTP request of any HTTP method:

req1 <- HttpRequest$new(
  url = "https://httpbin.org/get",
  opts = list(verbose = TRUE),
  headers = list(foo = "bar")
)$get()
req2 <- HttpRequest$new(url = "https://httpbin.org/post")$post()
out <- AsyncVaried$new(req1, req2)

Execute the requests

out$request()

Then functions get applied to all responses:

out$status()
#> [[1]]
#> <Status code: 200>
#>   Message: OK
#>   Explanation: Request fulfilled, document follows
#> 
#> [[2]]
#> <Status code: 200>
#>   Message: OK
#>   Explanation: Request fulfilled, document follows
out$parse()
#> [1] "{\n  \"args\": {}, \n  \"headers\": {\n    \"Accept\": \"application/json, text/xml, application/xml, */*\", \n    \"Accept-Encoding\": \"gzip, deflate\", \n    \"Connection\": \"close\", \n    \"Foo\": \"bar\", \n    \"Host\": \"httpbin.org\", \n    \"User-Agent\": \"R (3.4.3 x86_64-apple-darwin15.6.0 x86_64 darwin15.6.0)\"\n  }, \n  \"origin\": \"136.152.209.44\", \n  \"url\": \"https://httpbin.org/get\"\n}\n"                                                                                                                                   
#> [2] "{\n  \"args\": {}, \n  \"data\": \"\", \n  \"files\": {}, \n  \"form\": {}, \n  \"headers\": {\n    \"Accept\": \"application/json, text/xml, application/xml, */*\", \n    \"Accept-Encoding\": \"gzip, deflate\", \n    \"Connection\": \"close\", \n    \"Content-Length\": \"0\", \n    \"Content-Type\": \"application/x-www-form-urlencoded\", \n    \"Host\": \"httpbin.org\", \n    \"User-Agent\": \"libcurl/7.54.0 r-curl/3.1 crul/0.5.2\"\n  }, \n  \"json\": null, \n  \"origin\": \"136.152.209.44\", \n  \"url\": \"https://httpbin.org/post\"\n}\n"

TO DO

http caching

Add integration for:

for flexible and easy HTTP request caching

Meta