req_throttle {httr2}

Rate limit a request by automatically adding a delay

Description

Use req_throttle() to ensure that repeated calls to req_perform() never exceed a specified rate.

Usage

req_throttle(req, rate, realm = NULL)

Arguments

req

A request.

rate

Maximum rate, i.e. maximum number of requests per second. Usually easiest expressed as a fraction, number_of_requests / number_of_seconds, e.g. 15 requests per minute is 15 / 60.

realm

A string that uniquely identifies the throttle pool to use (throttling limits always apply per pool). If not supplied, defaults to the hostname of the request.

Value

A modified HTTP request.

See Also

req_retry() for another way of handling rate-limited APIs.

Examples

# Ensure we never send more than 30 requests a minute
req <- request(example_url()) |>
  req_throttle(rate = 30 / 60)

resp <- req_perform(req)
throttle_status()
resp <- req_perform(req)
throttle_status()