Async: Simple async client

Description

An async client to work with many URLs, but all with the same HTTP method

Arguments

Value

a list, with objects of class HttpResponse(). Responses are returned in the order they are passed in. We print the first 10.

Failure behavior

HTTP requests mostly fail in ways that you are probably familiar with, including when there's a 400 response (the URL not found), and when the server made a mistake (a 500 series HTTP status code).

But requests can fail sometimes where there is no HTTP status code, and no agreed upon way to handle it other than to just fail immediately.

When a request fails when using synchronous requests (see HttpClient) you get an error message that stops your code progression immediately saying for example:

"Could not resolve host: https://foo.com"
"Failed to connect to foo.com"
"Resolving timed out after 10 milliseconds"

However, for async requests we don't want to fail immediately because that would stop the subsequent requests from occurring. Thus, when we find that a request fails for one of the reasons above we give back a HttpResponse object just like any other response, and:

capture the error message and put it in the content slot of the response object (thus calls to content and parse() work correctly)
give back a 0 HTTP status code. we handle this specially when testing whether the request was successful or not with e.g., the success() method

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.

Public fields

urls: (character) one or more URLs
opts: any curl options
proxies: named list of headers
auth: an object of class auth
headers: named list of headers

Methods

Public methods

Method `print()`

print method for Async objects

Usage

Async$print(x, ...)

Arguments

x: self

...

ignored

Method `new()`

Create a new Async object

Usage

Async$new(urls, opts, proxies, auth, headers)

Arguments

urls: (character) one or more URLs

opts

any curl options

proxies

a proxy() object

auth

an auth() object

headers

named list of headers

Returns

A new Async object.

Method `get()`

execute the GET http verb for the urls

Usage

Async$get(path = NULL, query = list(), disk = NULL, stream = NULL, ...)

Arguments

path: (character) URL path, appended to the base URL

query

(list) query terms, as a named 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

...

curl options, only those in the acceptable set from curl::curl_options() except the following: httpget, httppost, post, postfields, postfieldsize, and customrequest

Examples

\dontrun{
(cc <- Async$new(urls = c(
    'https://hb.opencpu.org/',
    'https://hb.opencpu.org/get?a=5',
    'https://hb.opencpu.org/get?foo=bar'
  )))
(res <- cc$get())
}

Method `post()`

execute the POST http verb for the urls

Usage

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

Arguments

path: (character) URL path, appended to the base URL

query

(list) query terms, as a named list

body

body as an R list

encode

one of form, multipart, json, or raw

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

...

curl options, only those in the acceptable set from curl::curl_options() except the following: httpget, httppost, post, postfields, postfieldsize, and customrequest

Method `put()`

execute the PUT http verb for the urls

Usage

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

Arguments

path: (character) URL path, appended to the base URL

query

(list) query terms, as a named list

body

body as an R list

encode

one of form, multipart, json, or raw

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

...

curl options, only those in the acceptable set from curl::curl_options() except the following: httpget, httppost, post, postfields, postfieldsize, and customrequest

Method `patch()`

execute the PATCH http verb for the urls

Usage

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

Arguments

path: (character) URL path, appended to the base URL

query

(list) query terms, as a named list

body

body as an R list

encode

one of form, multipart, json, or raw

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

...

curl options, only those in the acceptable set from curl::curl_options() except the following: httpget, httppost, post, postfields, postfieldsize, and customrequest

Method `delete()`

execute the DELETE http verb for the urls

Usage

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

Arguments

path: (character) URL path, appended to the base URL

query

(list) query terms, as a named list

body

body as an R list

encode

one of form, multipart, json, or raw

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

...

curl options, only those in the acceptable set from curl::curl_options() except the following: httpget, httppost, post, postfields, postfieldsize, and customrequest

Method `head()`

execute the HEAD http verb for the urls

Usage

Async$head(path = NULL, ...)

Arguments

path: (character) URL path, appended to the base URL

...

curl options, only those in the acceptable set from curl::curl_options() except the following: httpget, httppost, post, postfields, postfieldsize, and customrequest

Method `retry()`

execute the RETRY http verb for the urls. see HttpRequest$retry method for parameters

Usage

Async$retry(...)

Arguments

...: curl options, only those in the acceptable set from curl::curl_options() except the following: httpget, httppost, post, postfields, postfieldsize, and customrequest

Method `verb()`

execute any supported HTTP verb

Usage

Async$verb(verb, ...)

Arguments

verb: (character) a supported HTTP verb: get, post, put, patch, delete, head.

...

curl options, only those in the acceptable set from curl::curl_options() except the following: httpget, httppost, post, postfields, postfieldsize, and customrequest

Examples

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

Method `clone()`

The objects of this class are cloneable with this method.

Usage

Async$clone(deep = FALSE)

Arguments

deep: Whether to make a deep clone.

Details

See HttpClient() for information on parameters.

Examples

Run this code

if (FALSE) {
cc <- Async$new(
  urls = c(
    'https://hb.opencpu.org/',
    'https://hb.opencpu.org/get?a=5',
    'https://hb.opencpu.org/get?foo=bar'
  )
)
cc
(res <- cc$get())
res[[1]]
res[[1]]$url
res[[1]]$success()
res[[1]]$status_http()
res[[1]]$response_headers
res[[1]]$method
res[[1]]$content
res[[1]]$parse("UTF-8")
lapply(res, function(z) z$parse("UTF-8"))

# curl options/headers with async
urls = c(
 'https://hb.opencpu.org/',
 'https://hb.opencpu.org/get?a=5',
 'https://hb.opencpu.org/get?foo=bar'
)
cc <- Async$new(urls = urls, 
  opts = list(verbose = TRUE),
  headers = list(foo = "bar")
)
cc
(res <- cc$get())

# using auth with async
dd <- Async$new(
  urls = rep('https://hb.opencpu.org/basic-auth/user/passwd', 3),
  auth = auth(user = "foo", pwd = "passwd"),
  opts = list(verbose = TRUE)
)
dd
res <- dd$get()
res
vapply(res, function(z) z$status_code, double(1))
vapply(res, function(z) z$success(), logical(1))
lapply(res, function(z) z$parse("UTF-8"))

# failure behavior
## e.g. when a URL doesn't exist, a timeout, etc.
urls <- c("http://stuffthings.gvb", "https://foo.com", 
  "https://hb.opencpu.org/get")
conn <- Async$new(urls = urls)
res <- conn$get()
res[[1]]$parse("UTF-8") # a failure
res[[2]]$parse("UTF-8") # a failure
res[[3]]$parse("UTF-8") # a success

# retry
urls = c("https://hb.opencpu.org/status/404", "https://hb.opencpu.org/status/429")
conn <- Async$new(urls = urls)
res <- conn$retry(verb="get")
}

## ------------------------------------------------
## Method `Async$get`
## ------------------------------------------------

if (FALSE) {
(cc <- Async$new(urls = c(
    'https://hb.opencpu.org/',
    'https://hb.opencpu.org/get?a=5',
    'https://hb.opencpu.org/get?foo=bar'
  )))
(res <- cc$get())
}

## ------------------------------------------------
## Method `Async$verb`
## ------------------------------------------------

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

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Description

Arguments

Value

Failure behavior

R6 classes

Public fields

Methods

Public methods

Method print()

Usage

Arguments

Method new()

Usage

Arguments

Returns

Method get()

Usage

Arguments

Examples

Method post()

Usage

Arguments

Method put()

Usage

Arguments

Method patch()

Usage

Arguments

Method delete()

Usage

Arguments

Method head()

Usage

Arguments

Method retry()

Usage

Arguments

Method verb()

Usage

Arguments

Examples

Method clone()

Usage

Arguments

Details

See Also

Examples

Method `print()`

Method `new()`

Method `get()`

Method `post()`

Method `put()`

Method `patch()`

Method `delete()`

Method `head()`

Method `retry()`

Method `verb()`

Method `clone()`