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HTTP client for OpenResty

local http = require'resty.http'

Lua HTTP client cosocket driver for OpenResty.


Production ready.


  • HTTP 1.0 and 1.1
  • SSL
  • Streaming interface to the response body, for predictable memory usage
  • Alternative simple interface for singleshot requests without manual connection step
  • Chunked and non-chunked transfer encodings
  • Keepalive
  • Pipelining
  • Trailers



lua_package_path "/path/to/lua-resty-http/lib/?.lua;;";

server {

  location /simpleinterface {
    resolver;  # use Google's open DNS server for an example

    content_by_lua_block {

      -- For simple singleshot requests, use the URI interface.
      local http = require "resty.http"
      local httpc =
      local res, err = httpc:request_uri("", {
        method = "POST",
        body = "a=1&b=2",
        headers = {
          ["Content-Type"] = "application/x-www-form-urlencoded",
        keepalive_timeout = 60,
        keepalive_pool = 10

      if not res then
        ngx.say("failed to request: ", err)

      -- In this simple form, there is no manual connection step, so the body is read
      -- all in one go, including any trailers, and the connection closed or keptalive
      -- for you.

      ngx.status = res.status

      for k,v in pairs(res.headers) do


  location /genericinterface {
    content_by_lua_block {

      local http = require "resty.http"
      local httpc =

      -- The generic form gives us more control. We must connect manually.
      httpc:connect("", 80)

      -- And request using a path, rather than a full URI.
      local res, err = httpc:request({
          path = "/helloworld",
          headers = {
              ["Host"] = "",

      if not res then
        ngx.say("failed to request: ", err)

      -- Now we can use the body_reader iterator, to stream the body according to our desired chunk size.
      local reader = res.body_reader

        local chunk, err = reader(8192)
        if err then
          ngx.log(ngx.ERR, err)

        if chunk then
          -- process
      until not chunk

      local ok, err = httpc:set_keepalive()
      if not ok then
        ngx.say("failed to set keepalive: ", err)



syntax: httpc =

Creates the http object. In case of failures, returns nil and a string describing the error.


syntax: ok, err = httpc:connect(host, port, options_table?)

syntax: ok, err = httpc:connect("unix:/path/to/unix.sock", options_table?)

Attempts to connect to the web server.

Before actually resolving the host name and connecting to the remote backend, this method will always look up the connection pool for matched idle connections created by previous calls of this method.

An optional Lua table can be specified as the last argument to this method to specify various connect options:

  • pool
    Specifies a custom name for the connection pool being used. If omitted, then the connection pool name will be generated from the string template <host>:<port> or <unix-socket-path>.


syntax: ok, err = httpc:connect_proxy(proxy_uri, scheme, host, port, proxy_authorization)

Attempts to connect to the web server through the given proxy server. The method accepts the following arguments:

  • proxy_uri - Full URI of the proxy server to use (e.g. Note: Only http protocol is supported.
  • scheme - The protocol to use between the proxy server and the remote host (http or https). If https is specified as the scheme, connect_proxy() makes a CONNECT request to establish a TCP tunnel to the remote host through the proxy server.
  • host - The hostname of the remote host to connect to.
  • port - The port of the remote host to connect to.
  • proxy_authorization - The Proxy-Authorization header value sent to the proxy server via CONNECT when the scheme is https.

If an error occurs during the connection attempt, this method returns nil with a string describing the error. If the connection was successfully established, the method returns 1.

There’s a few key points to keep in mind when using this api:

  • If the scheme is https, you need to perform the TLS handshake with the remote server manually using the ssl_handshake() method before sending any requests through the proxy tunnel.
  • If the scheme is http, you need to ensure that the requests you send through the connections conforms to RFC 7230 and especially Section 5.3.2. which states that the request target must be in absolute form. In practice, this means that when you use send_request(), the path must be an absolute URI to the resource (e.g. instead of just /index.html).


syntax: httpc:set_timeout(time)

Sets the timeout (in ms) protection for subsequent operations, including the connect method.


syntax: httpc:set_timeouts(connect_timeout, send_timeout, read_timeout)

Sets the connect timeout threshold, send timeout threshold, and read timeout threshold, respectively, in milliseconds, for subsequent socket operations (connect, send, receive, and iterators returned from receiveuntil).


syntax: session, err = httpc:ssl_handshake(session, host, verify)

Performs an SSL handshake on the TCP connection, only available in ngx_lua > v0.9.11

See docs for ngx.socket.tcp for details.


syntax: ok, err = httpc:set_keepalive(max_idle_timeout, pool_size)

Attempts to puts the current connection into the ngx_lua cosocket connection pool.

You can specify the max idle timeout (in ms) when the connection is in the pool and the maximal size of the pool every nginx worker process.

Only call this method in the place you would have called the close method instead. Calling this method will immediately turn the current http object into the closed state. Any subsequent operations other than connect() on the current object will return the closed error.

Note that calling this instead of close is “safe” in that it will conditionally close depending on the type of request. Specifically, a 1.0 request without Connection: Keep-Alive will be closed, as will a 1.1 request with Connection: Close.

In case of success, returns 1. In case of errors, returns nil, err. In the case where the connection is conditionally closed as described above, returns 2 and the error string connection must be closed.


syntax: httpc:set_proxy_options(opts)

Configure an http proxy to be used with this client instance. The opts is a table that accepts the following fields:

  • http_proxy - an URI to a proxy server to be used with http requests
  • http_proxy_authorization - a default Proxy-Authorization header value to be used with http_proxy, e.g. Basic ZGVtbzp0ZXN0, which will be overriden if the Proxy-Authorization request header is present.
  • https_proxy - an URI to a proxy server to be used with https requests
  • https_proxy_authorization - as http_proxy_authorization but for use with https_proxy.
  • no_proxy - a comma separated list of hosts that should not be proxied.

Note that proxy options are only applied when using the high-level request_uri() API.


syntax: times, err = httpc:get_reused_times()

This method returns the (successfully) reused times for the current connection. In case of error, it returns nil and a string describing the error.

If the current connection does not come from the built-in connection pool, then this method always returns 0, that is, the connection has never been reused (yet). If the connection comes from the connection pool, then the return value is always non-zero. So this method can also be used to determine if the current connection comes from the pool.


syntax: ok, err = http:close()

Closes the current connection and returns the status.

In case of success, returns 1. In case of errors, returns nil with a string describing the error.



syntax: res, err = httpc:request(params)

Returns a res table or nil and an error message.

The params table accepts the following fields:

  • version The HTTP version number, currently supporting 1.0 or 1.1.
  • method The HTTP method string.
  • path The path string.
  • query The query string, presented as either a literal string or Lua table..
  • headers A table of request headers.
  • body The request body as a string, or an iterator function (see get_client_body_reader).
  • ssl_verify Verify SSL cert matches hostname

When the request is successful, res will contain the following fields:

  • status The status code.
  • reason The status reason phrase.
  • headers A table of headers. Multiple headers with the same field name will be presented as a table of values.
  • has_body A boolean flag indicating if there is a body to be read.
  • body_reader An iterator function for reading the body in a streaming fashion.
  • read_body A method to read the entire body into a string.
  • read_trailers A method to merge any trailers underneath the headers, after reading the body.


syntax: res, err = httpc:request_uri(uri, params)

The simple interface. Options supplied in the params table are the same as in the generic interface, and will override components found in the uri itself.

There are 3 additional parameters for controlling keepalives:

  • keepalive Set to false to disable keepalives and immediately close the connection.
  • keepalive_timeout The maximal idle timeout (ms). Defaults to lua_socket_keepalive_timeout.
  • keepalive_pool The maximum number of connections in the pool. Defaults to lua_socket_pool_size.

In this mode, there is no need to connect manually first. The connection is made on your behalf, suiting cases where you simply need to grab a URI without too much hassle.

Additionally there is no ability to stream the response body in this mode. If the request is successful, res will contain the following fields:

  • status The status code.
  • headers A table of headers.
  • body The response body as a string.


syntax: responses, err = httpc:request_pipeline(params)

This method works as per the request method above, but params is instead a table of param tables. Each request is sent in order, and responses is returned as a table of response handles. For example:

local responses = httpc:request_pipeline{
    path = "/b",
    path = "/c",
    path = "/d",

for i,r in ipairs(responses) do
  if r.status then

Due to the nature of pipelining, no responses are actually read until you attempt to use the response fields (status / headers etc). And since the responses are read off in order, you must read the entire body (and any trailers if you have them), before attempting to read the next response.

Note this doesn’t preclude the use of the streaming response body reader. Responses can still be streamed, so long as the entire body is streamed before attempting to access the next response.

Be sure to test at least one field (such as status) before trying to use the others, in case a socket read error has occurred.



The body_reader iterator can be used to stream the response body in chunk sizes of your choosing, as follows:

local reader = res.body_reader

  local chunk, err = reader(8192)
  if err then
    ngx.log(ngx.ERR, err)

  if chunk then
    -- process
until not chunk

If the reader is called with no arguments, the behaviour depends on the type of connection. If the response is encoded as chunked, then the iterator will return the chunks as they arrive. If not, it will simply return the entire body.

Note that the size provided is actually a maximum size. So in the chunked transfer case, you may get chunks smaller than the size you ask, as a remainder of the actual HTTP chunks.


syntax: body, err = res:read_body()

Reads the entire body into a local string.


syntax: res:read_trailers()

This merges any trailers underneath the res.headers table itself. Must be called after reading the body.


There are two convenience methods for when one simply wishes to proxy the current request to the connected upstream, and safely send it downstream to the client, as a reverse proxy. A complete example:

local http = require "resty.http"
local httpc =

local ok, err = httpc:connect(HOST, PORT)

if not ok then
  ngx.log(ngx.ERR, err)



syntax: local res, err = httpc:proxy_request(request_body_chunk_size?)

Performs a request using the current client request arguments, effectively proxying to the connected upstream. The request body will be read in a streaming fashion, according to request_body_chunk_size (see documentation on the client body reader below).


syntax: httpc:proxy_response(res, chunksize?)

Sets the current response based on the given res. Ensures that hop-by-hop headers are not sent downstream, and will read the response according to chunksize (see documentation on the body reader above).



syntax: local scheme, host, port, path, query? = unpack(httpc:parse_uri(uri, query_in_path?))

This is a convenience function allowing one to more easily use the generic interface, when the input data is a URI.

As of version 0.10, the optional query_in_path parameter was added, which specifies whether the querystring is to be included in the path return value, or separately as its own return value. This defaults to true in order to maintain backwards compatibility. When set to false, path will only include the path, and query will contain the URI args, not including the ? delimiter.


syntax: reader, err = httpc:get_client_body_reader(chunksize?, sock?)

Returns an iterator function which can be used to read the downstream client request body in a streaming fashion. You may also specify an optional default chunksize (default is 65536), or an already established socket in place of the client request.


local req_reader = httpc:get_client_body_reader()

  local chunk, err = req_reader(8192)
  if err then
    ngx.log(ngx.ERR, err)

  if chunk then
    -- process
until not chunk

This iterator can also be used as the value for the body field in request params, allowing one to stream the request body into a proxied upstream request.

local client_body_reader, err = httpc:get_client_body_reader()

local res, err = httpc:request{
   path = "/helloworld",
   body = client_body_reader,

Last updated: 2 years ago | Edit on GitHub

Pkg type:Lua
Version: v0.13-8-ge6bc606
Last commit:
Author: James Hurst
License: BSD

Requires: none

Required by: none