Simple async client

Description

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

Details

See HttpClient() for information on parameters.

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

Methods

Public methods

• Async$print()

• Async$new()

• Async$get()

• Async$post()

• Async$put()

• Async$patch()

• Async$delete()

• Async$head()

• Async$retry()

• Async$verb()

• Async$clone()

Method print()

print method for Async objects

Usage

Async$print(x, ...)

Arguments

Method new()

Create a new Async object

Usage

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

Arguments

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

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

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

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

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

Method head()

execute the HEAD http verb for the urls

Usage

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

Arguments

Method retry()

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

Usage

Async$retry(...)

Arguments

Method verb()

execute any supported HTTP verb

Usage

Async$verb(verb, ...)

Arguments

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

See Also

Other async: AsyncQueue, AsyncVaried, HttpRequest

Examples

## Not run: 
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")

## End(Not run)

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

## Not run: 
(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())

## End(Not run)

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

## Not run: 
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"))

## End(Not run)