Read a streaming body a chunk at a time — resp_stream

resp_stream_raw() retrieves bytes (raw vectors).
resp_stream_lines() retrieves lines of text (character vectors).
resp_stream_sse() retrieves a single server-sent event.
resp_stream_aws() retrieves a single event from an AWS stream (i.e. mime type `application/vnd.amazon.eventstream“).

Use resp_stream_is_complete() to determine if there is further data waiting on the stream.

resp_stream_raw(resp, kb = 32)

resp_stream_lines(resp, lines = 1, max_size = Inf, warn = TRUE)

resp_stream_sse(resp, max_size = Inf)

resp_stream_aws(resp, max_size = Inf)

# S3 method for class 'httr2_response'
close(con, ...)

resp_stream_is_complete(resp)

Arguments

resp, con: A streaming response created by req_perform_connection().
kb: How many kilobytes (1024 bytes) of data to read.
lines: The maximum number of lines to return at once.
max_size: The maximum number of bytes to buffer; once this number of bytes has been exceeded without a line/event boundary, an error is thrown.
warn: Like readLines(): warn if the connection ends without a final EOL.
...: Not used; included for compatibility with generic.

Value

resp_stream_raw(): a raw vector.
resp_stream_lines(): a character vector.
resp_stream_sse(): a list with components type, data, and id. type, data, and id are always strings; data and id may be empty strings.
resp_stream_aws(): a list with components headers and body. body will be automatically parsed if the event contents a :content-type header with application/json.

resp_stream_sse() and resp_stream_aws() will return NULL to signal that the end of the stream has been reached or, if in nonblocking mode, that no event is currently available.

Examples

req <- request(example_url()) |>
  req_template("GET /stream/:n", n = 5)

con <- req |> req_perform_connection()
while (!resp_stream_is_complete(con)) {
  lines <- con |> resp_stream_lines(2)
  cat(length(lines), " lines received\n", sep = "")
}
#> 2 lines received
#> 2 lines received
#> 1 lines received
close(con)

# You can also see what's happening by setting verbosity
con <- req |> req_perform_connection(verbosity = 2)
#> -> GET /stream/5 HTTP/1.1
#> -> Host: 127.0.0.1:44765
#> -> User-Agent: httr2/1.2.1 r-curl/6.4.0 libcurl/7.81.0
#> -> Accept: */*
#> -> Accept-Encoding: deflate, gzip, br, zstd
#> -> 
#> <- HTTP/1.1 200 OK
#> <- Date: Tue, 29 Jul 2025 19:05:17 GMT
#> <- Content-Type: application/json
#> <- Transfer-Encoding: chunked
#> <- 
while (!resp_stream_is_complete(con)) {
  lines <- con |> resp_stream_lines(2)
}
#> << {"url":"http://127.0.0.1:44765/stream/5","args":{},"headers":{"Host":"127.0.0.1:44765","User-Agent":"httr2/1.2.1 r-curl/6.4.0 libcurl/7.81.0","Accept":"*/*","Accept-Encoding":"deflate, gzip, br, zstd"},"origin":"127.0.0.1","id":0}<< {"url":"http://127.0.0.1:44765/stream/5","args":{},"headers":{"Host":"127.0.0.1:44765","User-Agent":"httr2/1.2.1 r-curl/6.4.0 libcurl/7.81.0","Accept":"*/*","Accept-Encoding":"deflate, gzip, br, zstd"},"origin":"127.0.0.1","id":1}
#> << {"url":"http://127.0.0.1:44765/stream/5","args":{},"headers":{"Host":"127.0.0.1:44765","User-Agent":"httr2/1.2.1 r-curl/6.4.0 libcurl/7.81.0","Accept":"*/*","Accept-Encoding":"deflate, gzip, br, zstd"},"origin":"127.0.0.1","id":2}<< {"url":"http://127.0.0.1:44765/stream/5","args":{},"headers":{"Host":"127.0.0.1:44765","User-Agent":"httr2/1.2.1 r-curl/6.4.0 libcurl/7.81.0","Accept":"*/*","Accept-Encoding":"deflate, gzip, br, zstd"},"origin":"127.0.0.1","id":3}
#> << {"url":"http://127.0.0.1:44765/stream/5","args":{},"headers":{"Host":"127.0.0.1:44765","User-Agent":"httr2/1.2.1 r-curl/6.4.0 libcurl/7.81.0","Accept":"*/*","Accept-Encoding":"deflate, gzip, br, zstd"},"origin":"127.0.0.1","id":4}
close(con)