rOpenSci: The crul package

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

Package API:

• HttpClient - Main interface to making HTTP requests. Synchronous requests only.
• HttpResponse - HTTP response object, used for all responses across the different clients.
• Paginator - Auto-paginate through requests - supports a subset of all possible pagination scenarios - will fill out more scenarios soon
• Async - Asynchronous HTTP requests - a simple interface for many URLS - whose interface is similar to HttpClient - all URLs are treated the same.
• AsyncVaried - Asynchronous HTTP requests - accepts any number of HttpRequest objects - with a different interface than HttpClient/Async due to the nature of handling requests with different HTTP methods, options, etc.
• HttpRequest - HTTP request object, used for AsyncVaried
• mock() - Turn on/off mocking, via webmockr
• auth() - Simple authentication helper
• proxy() - Proxy helper
• upload() - File upload helper
• set curl options globally: set_auth(), set_headers(), set_opts(), set_proxy(), and crul_settings()
• Writing to disk and streaming: available with both synchronous requests as well as async requests
• Hooks on requests and responses are available in the HttpClient method only, and allow you to trigger functions to run on requests or responses, or both. See ?hooks for the details and examples

Mocking:

crul now integrates with webmockr to mock HTTP requests. Checkout the http testing book

Caching:

crul also integrates with vcr to cache http requests/responses. Checkout the http testing book

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
#>   progress: FALSE
#>   hooks:

Makes an 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 64 65
#>  [26] 72 73 22 3a 20 7b 0a 20 20 20 20 22 41 22 3a 20 22 68 65 6c 6c 6f 20 77 6f
#>  [51] 72 6c 64 22 2c 20 0a 20 20 20 20 22 41 63 63 65 70 74 22 3a 20 22 61 70 70
#>  [76] 6c 69 63 61 74 69 6f 6e 2f 6a 73 6f 6e 2c 20 74 65 78 74 2f 78 6d 6c 2c 20
#> [101] 61 70 70 6c 69 63 61 74 69 6f 6e 2f 78 6d 6c 2c 20 2a 2f 2a 22 2c 20 0a 20
#> [126] 20 20 20 22 41 63 63 65 70 74 2d 45 6e 63 6f 64 69 6e 67 22 3a 20 22 67 7a
#> [151] 69 70 2c 20 64 65 66 6c 61 74 65 22 2c 20 0a 20 20 20 20 22 48 6f 73 74 22
#> [176] 3a 20 22 68 74 74 70 62 69 6e 2e 6f 72 67 22 2c 20 0a 20 20 20 20 22 55 73
#> [201] 65 72 2d 41 67 65 6e 74 22 3a 20 22 6c 69 62 63 75 72 6c 2f 37 2e 35 34 2e
#> [226] 30 20 72 2d 63 75 72 6c 2f 34 2e 32 20 63 72 75 6c 2f 30 2e 39 2e 31 2e 39
#> [251] 32 30 30 22 0a 20 20 7d 2c 20 0a 20 20 22 6f 72 69 67 69 6e 22 3a 20 22 31
#> [276] 39 32 2e 31 33 32 2e 36 31 2e 33 35 2c 20 31 39 32 2e 31 33 32 2e 36 31 2e
#> [301] 33 35 22 2c 20 0a 20 20 22 75 72 6c 22 3a 20 22 68 74 74 70 73 3a 2f 2f 68
#> [326] 74 74 70 62 69 6e 2e 6f 72 67 2f 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/4.2 crul/0.9.1.9200"
#> 
#> $`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"
#> 
#> $`access-control-allow-credentials`
#> [1] "true"
#> 
#> $`access-control-allow-origin`
#> [1] "*"
#> 
#> $`content-encoding`
#> [1] "gzip"
#> 
#> $`content-type`
#> [1] "application/json"
#> 
#> $date
#> [1] "Fri, 22 Nov 2019 19:27:43 GMT"
#> 
#> $`referrer-policy`
#> [1] "no-referrer-when-downgrade"
#> 
#> $server
#> [1] "nginx"
#> 
#> $`x-content-type-options`
#> [1] "nosniff"
#> 
#> $`x-frame-options`
#> [1] "DENY"
#> 
#> $`x-xss-protection`
#> [1] "1; mode=block"
#> 
#> $`content-length`
#> [1] "232"
#> 
#> $connection
#> [1] "keep-alive"

All response headers - e.g., intermediate headers

res$response_headers_all

And you can parse the content with parse()

res$parse()
#> No encoding supplied: defaulting to UTF-8.
#> [1] "{\n  \"args\": {}, \n  \"headers\": {\n    \"A\": \"hello world\", \n    \"Accept\": \"application/json, text/xml, application/xml, */*\", \n    \"Accept-Encoding\": \"gzip, deflate\", \n    \"Host\": \"httpbin.org\", \n    \"User-Agent\": \"libcurl/7.54.0 r-curl/4.2 crul/0.9.1.9200\"\n  }, \n  \"origin\": \"192.132.61.35, 192.132.61.35\", \n  \"url\": \"https://httpbin.org/get\"\n}\n"
jsonlite::fromJSON(res$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"
#> 
#> $headers$Host
#> [1] "httpbin.org"
#> 
#> $headers$`User-Agent`
#> [1] "libcurl/7.54.0 r-curl/4.2 crul/0.9.1.9200"
#> 
#> 
#> $origin
#> [1] "192.132.61.35, 192.132.61.35"
#> 
#> $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    \"Foo\": \"bar\", \n    \"Host\": \"httpbin.org\", \n    \"User-Agent\": \"R (3.6.1 x86_64-apple-darwin15.6.0 x86_64 darwin15.6.0)\"\n  }, \n  \"origin\": \"192.132.61.35, 192.132.61.35\", \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    \"Content-Length\": \"0\", \n    \"Content-Type\": \"application/x-www-form-urlencoded\", \n    \"Host\": \"httpbin.org\", \n    \"User-Agent\": \"libcurl/7.54.0 r-curl/4.2 crul/0.9.1.9200\"\n  }, \n  \"json\": null, \n  \"origin\": \"192.132.61.35, 192.132.61.35\", \n  \"url\": \"https://httpbin.org/post\"\n}\n"

Progress bars

library(httr)
x <- HttpClient$new(
  url = "https://httpbin.org/bytes/102400", 
  progress = progress()
)
z <- x$get()
|==============================================| 100%

TO DO

• …

Meta

• Please report any issues or bugs.
• License: MIT
• Get citation information for crul in R doing citation(package = 'crul')
• Please note that this project is released with a Contributor Code of Conduct. By participating in this project you agree to abide by its terms.