AsyncVaried: Async client for different request types

Description

Async client for different request types

Arguments

..., .list

Any number of objects of class HttpRequest(), must supply inputs to one of these parameters, but not both

Value

An object of class AsyncVaried with variables and methods. HttpResponse objects 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

Details

Methods

request(): Execute asynchronous requests - returns: nothing, responses stored inside object, though will print messages if you choose verbose output
requests(): list requests - returns: a list of HttpRequest objects, empty list before requests made
responses(): list responses - returns: a list of HttpResponse objects, empty list before requests made
parse(encoding = "UTF-8"): parse content - returns: character vector, empty character vector before requests made
status_code(): (integer) HTTP status codes - returns: numeric vector, empty numeric vector before requests made
status(): (list) HTTP status objects - returns: a list of http_code objects, empty list before requests made
content(): raw content - returns: raw list, empty list before requests made
times(): curl request times - returns: list of named numeric vectors, empty list before requests made

Examples

Run this code

# NOT RUN {
# pass in requests via ...
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()

# Create an AsyncVaried object
out <- AsyncVaried$new(req1, req2)

# before you make requests, the methods return empty objects
out$status()
out$status_code()
out$content()
out$times()
out$parse()
out$responses()

# make requests
out$request()

# access various parts
## http status objects
out$status()
## status codes
out$status_code()
## content (raw data)
out$content()
## times
out$times()
## parsed content
out$parse()
## response objects
out$responses()

# use $verb() method to select http verb
method <- "post"
req1 <- HttpRequest$new(
  url = "https://httpbin.org/post",
  opts = list(verbose = TRUE),
  headers = list(foo = "bar")
)$verb(method)
req2 <- HttpRequest$new(url = "https://httpbin.org/post")$verb(method)
out <- AsyncVaried$new(req1, req2)
out
out$request()
out$responses()

# pass in requests in a list via .list param
reqlist <- list(
  HttpRequest$new(url = "https://httpbin.org/get")$get(),
  HttpRequest$new(url = "https://httpbin.org/post")$post(),
  HttpRequest$new(url = "https://httpbin.org/put")$put(),
  HttpRequest$new(url = "https://httpbin.org/delete")$delete(),
  HttpRequest$new(url = "https://httpbin.org/get?g=5")$get(),
  HttpRequest$new(
    url = "https://httpbin.org/post")$post(body = list(y = 9)),
  HttpRequest$new(
    url = "https://httpbin.org/get")$get(query = list(hello = "world"))
)

out <- AsyncVaried$new(.list = reqlist)
out$request()
out$status()
out$status_code()
out$content()
out$times()
out$parse()

# using auth with async
url <- "https://httpbin.org/basic-auth/user/passwd"
auth <- auth(user = "user", pwd = "passwd")
reqlist <- list(
  HttpRequest$new(url = url, auth = auth)$get(),
  HttpRequest$new(url = url, auth = auth)$get(query = list(a=5)),
  HttpRequest$new(url = url, auth = auth)$get(query = list(b=3))
)
out <- AsyncVaried$new(.list = reqlist)
out$request()
out$status()
out$parse()

# failure behavior
## e.g. when a URL doesn't exist, a timeout, etc.
reqlist <- list(
  HttpRequest$new(url = "http://stuffthings.gvb")$get(),
  HttpRequest$new(url = "https://httpbin.org")$head(),
  HttpRequest$new(url = "https://httpbin.org", 
   opts = list(timeout_ms = 10))$head()
)
(tmp <- AsyncVaried$new(.list = reqlist))
tmp$request()
tmp$responses()
tmp$parse("UTF-8")

# access intemediate redirect headers
dois <- c("10.7202/1045307ar", "10.1242/jeb.088898", "10.1121/1.3383963")
reqlist <- list(
  HttpRequest$new(url = paste0("https://doi.org/", dois[1]))$get(),
  HttpRequest$new(url = paste0("https://doi.org/", dois[2]))$get(),
  HttpRequest$new(url = paste0("https://doi.org/", dois[3]))$get()
)
tmp <- AsyncVaried$new(.list = reqlist)
tmp$request()
tmp
lapply(tmp$responses(), "[[", "response_headers_all")
# }