Perform a request and handle data as it streams back
Source:R/req-perform-stream.R
req_perform_stream.Rd
After preparing a request, call req_perform_stream()
to perform the request
and handle the result with a streaming callback. This is useful for
streaming HTTP APIs where potentially the stream never ends.
The callback
will only be called if the result is successful. If you need
to stream an error response, you can use req_error()
to suppress error
handling so that the body is streamed to you.
Usage
req_perform_stream(
req,
callback,
timeout_sec = Inf,
buffer_kb = 64,
round = c("byte", "line")
)
Arguments
- req
A httr2 request object.
- callback
A single argument callback function. It will be called repeatedly with a raw vector whenever there is at least
buffer_kb
worth of data to process. It must returnTRUE
to continue streaming.- timeout_sec
Number of seconds to process stream for.
- buffer_kb
Buffer size, in kilobytes.
- round
How should the raw vector sent to
callback
be rounded? Choose"byte"
,"line"
, or supply your own function that takes a raw vector ofbytes
and returns the locations of possible cut points (orinteger()
if there are none).
Value
An HTTP response. The body will be empty if the request was
successful (since the callback
function will have handled it). The body
will contain the HTTP response body if the request was unsuccessful.
Examples
show_bytes <- function(x) {
cat("Got ", length(x), " bytes\n", sep = "")
TRUE
}
resp <- request(example_url()) |>
req_url_path("/stream-bytes/100000") |>
req_perform_stream(show_bytes, buffer_kb = 32)
#> Got 32768 bytes
#> Got 32768 bytes
#> Got 32768 bytes
#> Got 1696 bytes
resp
#> <httr2_response>
#> GET http://127.0.0.1:42095/stream-bytes/100000
#> Status: 200 OK
#> Content-Type: application/octet-stream
#> Body: None