HttpClient {crul}R Documentation

HTTP client

Description

Create and execute HTTP requests

Value

an HttpResponse object

R6 classes

This is an R6 class from the package R6. Find out more about R6 at https://r6.r-lib.org/. After creating an instance of an R6 class (e.g., x <- HttpClient$new(url = "https://hb.opencpu.org")) you can access values and methods on the object x.

handles

curl handles are re-used on the level of the connection object, that is, each HttpClient object is separate from one another so as to better separate connections.

If you don't pass in a curl handle to the handle parameter, it gets created when a HTTP verb is called. Thus, if you try to get handle after creating a HttpClient object only passing url parameter, handle will be NULL. If you pass a curl handle to the handle parameter, then you can get the handle from the HttpClient object. The response from a http verb request does have the handle in the handle slot.

Public fields

url

(character) a url

opts

(list) named list of curl options

proxies

a proxy() object

auth

an auth() object

headers

(list) named list of headers, see http-headers

handle

a handle()

progress

only supports httr::progress(), see progress

hooks

a named list, see hooks

Methods

Public methods

Method print()

print method for HttpClient objects

Usage
HttpClient$print(x, ...)
Arguments
x

self

...

ignored

Method new()

Create a new HttpClient object

Usage
HttpClient$new(
  url,
  opts,
  proxies,
  auth,
  headers,
  handle,
  progress,
  hooks,
  verbose
)
Arguments
url

(character) A url. One of url or handle required.

opts

any curl options

proxies

a proxy() object

auth

an auth() object

headers

named list of headers, see http-headers

handle

a handle()

progress

only supports httr::progress(), see progress

hooks

a named list, see hooks

verbose

a special handler for verbose curl output, accepts a function only. default is NULL. if used, verbose and debugfunction curl options are ignored if passed to opts on ⁠$new()⁠ and ignored if ... passed to a http method call

urls

(character) one or more URLs

Returns

A new HttpClient object

Method get()

Make a GET request

Usage
HttpClient$get(path = NULL, query = list(), disk = NULL, stream = NULL, ...)
Arguments
path

URL path, appended to the base URL

query

query terms, as a named list. any numeric values are passed through format() to prevent larger numbers from being scientifically formatted

disk

a path to write to. if NULL (default), memory used. See curl::curl_fetch_disk() for help.

stream

an R function to determine how to stream data. if NULL (default), memory used. See curl::curl_fetch_stream() for help

...

For retry, the options to be passed on to the method implementing the requested verb, including curl options. Otherwise, curl options, only those in the acceptable set from curl::curl_options() except the following: httpget, httppost, post, postfields, postfieldsize, and customrequest

Method post()

Make a POST request

Usage
HttpClient$post(
  path = NULL,
  query = list(),
  body = NULL,
  disk = NULL,
  stream = NULL,
  encode = "multipart",
  ...
)
Arguments
path

URL path, appended to the base URL

query

query terms, as a named list. any numeric values are passed through format() to prevent larger numbers from being scientifically formatted

body

body as an R list

disk

a path to write to. if NULL (default), memory used. See curl::curl_fetch_disk() for help.

stream

an R function to determine how to stream data. if NULL (default), memory used. See curl::curl_fetch_stream() for help

encode

one of form, multipart, json, or raw

...

For retry, the options to be passed on to the method implementing the requested verb, including curl options. Otherwise, curl options, only those in the acceptable set from curl::curl_options() except the following: httpget, httppost, post, postfields, postfieldsize, and customrequest

Method put()

Make a PUT request

Usage
HttpClient$put(
  path = NULL,
  query = list(),
  body = NULL,
  disk = NULL,
  stream = NULL,
  encode = "multipart",
  ...
)
Arguments
path

URL path, appended to the base URL

query

query terms, as a named list. any numeric values are passed through format() to prevent larger numbers from being scientifically formatted

body

body as an R list

disk

a path to write to. if NULL (default), memory used. See curl::curl_fetch_disk() for help.

stream

an R function to determine how to stream data. if NULL (default), memory used. See curl::curl_fetch_stream() for help

encode

one of form, multipart, json, or raw

...

For retry, the options to be passed on to the method implementing the requested verb, including curl options. Otherwise, curl options, only those in the acceptable set from curl::curl_options() except the following: httpget, httppost, post, postfields, postfieldsize, and customrequest

Method patch()

Make a PATCH request

Usage
HttpClient$patch(
  path = NULL,
  query = list(),
  body = NULL,
  disk = NULL,
  stream = NULL,
  encode = "multipart",
  ...
)
Arguments
path

URL path, appended to the base URL

query

query terms, as a named list. any numeric values are passed through format() to prevent larger numbers from being scientifically formatted

body

body as an R list

disk

a path to write to. if NULL (default), memory used. See curl::curl_fetch_disk() for help.

stream

an R function to determine how to stream data. if NULL (default), memory used. See curl::curl_fetch_stream() for help

encode

one of form, multipart, json, or raw

...

For retry, the options to be passed on to the method implementing the requested verb, including curl options. Otherwise, curl options, only those in the acceptable set from curl::curl_options() except the following: httpget, httppost, post, postfields, postfieldsize, and customrequest

Method delete()

Make a DELETE request

Usage
HttpClient$delete(
  path = NULL,
  query = list(),
  body = NULL,
  disk = NULL,
  stream = NULL,
  encode = "multipart",
  ...
)
Arguments
path

URL path, appended to the base URL

query

query terms, as a named list. any numeric values are passed through format() to prevent larger numbers from being scientifically formatted

body

body as an R list

disk

a path to write to. if NULL (default), memory used. See curl::curl_fetch_disk() for help.

stream

an R function to determine how to stream data. if NULL (default), memory used. See curl::curl_fetch_stream() for help

encode

one of form, multipart, json, or raw

...

For retry, the options to be passed on to the method implementing the requested verb, including curl options. Otherwise, curl options, only those in the acceptable set from curl::curl_options() except the following: httpget, httppost, post, postfields, postfieldsize, and customrequest

Method head()

Make a HEAD request

Usage
HttpClient$head(path = NULL, query = list(), ...)
Arguments
path

URL path, appended to the base URL

query

query terms, as a named list. any numeric values are passed through format() to prevent larger numbers from being scientifically formatted

...

For retry, the options to be passed on to the method implementing the requested verb, including curl options. Otherwise, curl options, only those in the acceptable set from curl::curl_options() except the following: httpget, httppost, post, postfields, postfieldsize, and customrequest

Method verb()

Use an arbitrary HTTP verb supported on this class Supported verbs: "get", "post", "put", "patch", "delete", "head". Also supports retry

Usage
HttpClient$verb(verb, ...)
Arguments
verb

an HTTP verb supported on this class: "get", "post", "put", "patch", "delete", "head". Also supports retry.

...

For retry, the options to be passed on to the method implementing the requested verb, including curl options. Otherwise, curl options, only those in the acceptable set from curl::curl_options() except the following: httpget, httppost, post, postfields, postfieldsize, and customrequest

Examples
\dontrun{
(x <- HttpClient$new(url = "https://hb.opencpu.org"))
x$verb('get')
x$verb('GET')
x$verb('GET', query = list(foo = "bar"))
x$verb('retry', 'GET', path = "status/400")
}

Method retry()

Retry a request

Usage
HttpClient$retry(
  verb,
  ...,
  pause_base = 1,
  pause_cap = 60,
  pause_min = 1,
  times = 3,
  terminate_on = NULL,
  retry_only_on = NULL,
  onwait = NULL
)
Arguments
verb

an HTTP verb supported on this class: "get", "post", "put", "patch", "delete", "head". Also supports retry.

...

For retry, the options to be passed on to the method implementing the requested verb, including curl options. Otherwise, curl options, only those in the acceptable set from curl::curl_options() except the following: httpget, httppost, post, postfields, postfieldsize, and customrequest

pause_base, pause_cap, pause_min

basis, maximum, and minimum for calculating wait time for retry. Wait time is calculated according to the exponential backoff with full jitter algorithm. Specifically, wait time is chosen randomly between pause_min and the lesser of pause_base * 2 and pause_cap, with pause_base doubling on each subsequent retry attempt. Use pause_cap = Inf to not terminate retrying due to cap of wait time reached.

times

the maximum number of times to retry. Set to Inf to not stop retrying due to exhausting the number of attempts.

terminate_on, retry_only_on

a vector of HTTP status codes. For terminate_on, the status codes for which to terminate retrying, and for retry_only_on, the status codes for which to retry the request.

onwait

a callback function if the request will be retried and a wait time is being applied. The function will be passed two parameters, the response object from the failed request, and the wait time in seconds. Note that the time spent in the function effectively adds to the wait time, so it should be kept simple.

Details

Retries the request given by verb until successful (HTTP response status < 400), or a condition for giving up is met. Automatically recognizes Retry-After and X-RateLimit-Reset headers in the response for rate-limited remote APIs.

Examples
\dontrun{
x <- HttpClient$new(url = "https://hb.opencpu.org")

# retry, by default at most 3 times
(res_get <- x$retry("GET", path = "status/400"))

# retry, but not for 404 NOT FOUND
(res_get <- x$retry("GET", path = "status/404", terminate_on = c(404)))

# retry, but only for exceeding rate limit (note that e.g. Github uses 403)
(res_get <- x$retry("GET", path = "status/429", retry_only_on = c(403, 429)))
}

Method handle_pop()

reset your curl handle

Usage
HttpClient$handle_pop()

Method url_fetch()

get the URL that would be sent (i.e., before executing the request) the only things that change the URL are path and query parameters; body and any curl options don't change the URL

Usage
HttpClient$url_fetch(path = NULL, query = list())
Arguments
path

URL path, appended to the base URL

query

query terms, as a named list. any numeric values are passed through format() to prevent larger numbers from being scientifically formatted

Returns

URL (character)

Examples
x <- HttpClient$new(url = "https://hb.opencpu.org")
x$url_fetch()
x$url_fetch('get')
x$url_fetch('post')
x$url_fetch('get', query = list(foo = "bar"))

Method clone()

The objects of this class are cloneable with this method.

Usage
HttpClient$clone(deep = FALSE)
Arguments
deep

Whether to make a deep clone.

Note

A little quirk about crul is that because user agent string can be passed as either a header or a curl option (both lead to a User-Agent header being passed in the HTTP request), we return the user agent string in the request_headers list of the response even if you pass in a useragent string as a curl option. Note that whether you pass in as a header like User-Agent or as a curl option like useragent, it is returned as request_headers$User-Agent so at least accessing it in the request headers is consistent.

See Also

http-headers, writing-options, cookies, hooks

Examples

## Not run: 
# set your own handle
(h <- handle("https://hb.opencpu.org"))
(x <- HttpClient$new(handle = h))
x$handle
x$url
(out <- x$get("get"))
x$handle
x$url
class(out)
out$handle
out$request_headers
out$response_headers
out$response_headers_all

# if you just pass a url, we create a handle for you
#  this is how most people will use HttpClient
(x <- HttpClient$new(url = "https://hb.opencpu.org"))
x$url
x$handle # is empty, it gets created when a HTTP verb is called
(r1 <- x$get('get'))
x$url
x$handle
r1$url
r1$handle
r1$content
r1$response_headers
r1$parse()

(res_get2 <- x$get('get', query = list(hello = "world")))
res_get2$parse()
library("jsonlite")
jsonlite::fromJSON(res_get2$parse())

# post request
(res_post <- x$post('post', body = list(hello = "world")))

## empty body request
x$post('post')

# put request
(res_put <- x$put('put'))

# delete request
(res_delete <- x$delete('delete'))

# patch request
(res_patch <- x$patch('patch'))

# head request
(res_head <- x$head())

# query params are URL encoded for you, so DO NOT do it yourself
## if you url encode yourself, it gets double encoded, and that's bad
(x <- HttpClient$new(url = "https://hb.opencpu.org"))
res <- x$get("get", query = list(a = 'hello world'))

# access intermediate headers in response_headers_all
x <- HttpClient$new("https://doi.org/10.1007/978-3-642-40455-9_52-1")
bb <- x$get()
bb$response_headers_all

## End(Not run)

## ------------------------------------------------
## Method `HttpClient$verb`
## ------------------------------------------------

## Not run: 
(x <- HttpClient$new(url = "https://hb.opencpu.org"))
x$verb('get')
x$verb('GET')
x$verb('GET', query = list(foo = "bar"))
x$verb('retry', 'GET', path = "status/400")

## End(Not run)

## ------------------------------------------------
## Method `HttpClient$retry`
## ------------------------------------------------

## Not run: 
x <- HttpClient$new(url = "https://hb.opencpu.org")

# retry, by default at most 3 times
(res_get <- x$retry("GET", path = "status/400"))

# retry, but not for 404 NOT FOUND
(res_get <- x$retry("GET", path = "status/404", terminate_on = c(404)))

# retry, but only for exceeding rate limit (note that e.g. Github uses 403)
(res_get <- x$retry("GET", path = "status/429", retry_only_on = c(403, 429)))

## End(Not run)

## ------------------------------------------------
## Method `HttpClient$url_fetch`
## ------------------------------------------------

x <- HttpClient$new(url = "https://hb.opencpu.org")
x$url_fetch()
x$url_fetch('get')
x$url_fetch('post')
x$url_fetch('get', query = list(foo = "bar"))
[Package crul version 1.5.0 Index]