如何在不等待响应的情况下发送GET请求 [英] How can I send a GET request without waiting for the response

问题描述

我正在尝试在ShinyApp内运行GET请求，但我不想等待响应，因为这将花费很长时间来处理，并且我并不需要在ShinyApp内真正需要响应，尽管状态代码会很好，但不是必须的。

I am trying to run a GET request inside a shinyApp, but I don't want to wait for the response as it would take quite a long time to process and I dont need really need the response inside the shinyApp, although a status code would be nice, but it is not obligatory.

或者是否有一个函数可以发送异步请求？就像将整个GET包装在一个Future / Promise中一样？

Or is there maybe a function, that sends an async request? Like wrapping the whole GET inside a future/promise?

当前，我在我的ShinyApp中有这个watchEvent：

Currently I have this observeEvent in my shinyApp:

  observeEvent(input$import, {
    httr::GET(url = "https://someurl/that/takes/a/long/time")
  })

是 curl_fetch_multi c $ c> curl 软件包适合该任务吗？

Is the curl_fetch_multi from the curl package suited for that task?

推荐答案

这是一种运行 GET 以会话内非阻塞方式（观察者不返回任何内容）异步获取：

Here is a way to run GET asynchronously and in a intra-session non-blocking manner (observer returning nothing):

library(shiny)
library(future)
library(promises)
library(future.callr)
library(httr)

plan(callr)

queryGoogle <- function(queryString) {
  myResponse <- httr::GET("http://google.com/", path = "search", query = list(q = queryString))
  return(myResponse)
}

ui <- fluidPage(
  br(),
  textOutput("time_output"),
  br(),
  textInput(inputId="query_input", label = NULL, value = "", placeholder = "Search google..."),
  actionButton("import", "Query"),
  hr(),
  textOutput("query_output")
)

server <- function(input, output, session) {
  futureData <- reactiveValues(response = NULL)

  observeEvent(input$import, {
    myFuture <- future({
      queryGoogle(isolate(input$query_input))
    })

    then(
      myFuture,
      onFulfilled = function(value) {
        futureData$response <- value
      },
      onRejected = NULL
    )
    return(NULL)
  })

  output$query_output <- renderPrint({
    req(futureData$response)
  })

  time <- reactive({
    invalidateLater(500, session)
    Sys.time()
  })

  output$time_output <- renderText({ paste("Something running in parallel:", time()) })
}

shinyApp(ui, server)

这是对我的答案的略微修改此处。

This is a slight modification of my answer here.

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