Module http | Tarantool
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Module http

The http module, specifically the http.client submodule, provides the functionality of an HTTP client with support for HTTPS and keepalive. It uses routines in the libcurl library.

Below is a list of all http functions.

Name Use Create an HTTP client instance
client_object:request() Perform an HTTP request
client_object:stat() Get a table with statistics[options])

Construct a new HTTP client instance.

  • options (table) – integer settings which are passed to libcurl.

The two possible options are max_connections and max_total_connections.

max_connections is the maximum number of entries in the cache. It affects libcurl CURLMOPT_MAXCONNECTS. The default is -1.

max_total_connections is the maximum number of active connections. It affects libcurl CURLMOPT_MAX_TOTAL_CONNECTIONS. It is ignored if the curl version is less than 7.30. The default is 0, which allows libcurl to scale accordingly to easily handles count.

The default option values are usually good enough but in rare cases it might be good to set them. In that case here are two tips.

  1. You may want to control the maximum number of sockets that a particular HTTP client uses simultaneously. If a system passes many requests to distinct hosts, then libcurl cannot reuse sockets. In this case setting max_total_connections may be useful, since it causes curl to avoid creating too many sockets which would not be used anyway.
  2. Do not set max_connections less than max_total_connections unless you are confident about your actions. When max_connections is less then max_total_connections, in some cases libcurl will not reuse sockets for requests that are going to the same host. If the limit is reached and a new request occurs, then libcurl will first create a new socket, send the request, wait for the first connection to be free, and close it, in order to avoid exceeding the max_connections cache size. In the worst case, libcurl will create a new socket for every request, even if all requests are going to the same host. See this Tarantool issue on Github for details.
Return:a new HTTP client instance


tarantool> http_client = require('http.client').new({max_connections = 5})
object client_object
client_object:request(method, url, body, opts)

If http_client is an HTTP client instance, http_client:request() will perform an HTTP request and, if there is a successful connection, will return a table with connection information.

  • method (string) – HTTP method, for example ‘GET’ or ‘POST’ or ‘PUT’
  • url (string) – location, for example ‘
  • body (string) – optional initial message, for example ‘My text string!’
  • opts (table) –

    table of connection options, with any of these components:

    • ca_file – path to an SSL certificate file to verify the peer with.
    • ca_path – path to a directory holding one or more certificates to verify the peer with.
    • headers – table of HTTP headers.
    • keepalive_idle – delay, in seconds, that the operating system will wait while the connection is idle before sending keepalive probes. See also CURLOPT_TCP_KEEPIDLE and the note below about keepalive_interval.
    • keepalive_interval – the interval, in seconds, that the operating system will wait between sending keepalive probes. See also CURLOPT_TCP_KEEPINTVL. If both keepalive_idle and keepalive_interval are set, then Tarantool will also set HTTP keepalive headers: Connection:Keep-Alive and Keep-Alive:timeout=<keepalive_idle>. Otherwise, Tarantool will send Connection:close.
    • low_speed_limit – set the “low speed limit” – the average transfer speed in bytes per second that the transfer should be below during “low speed time” seconds for the library to consider it to be too slow and abort. See also CURLOPT_LOW_SPEED_LIMIT.
    • low_speed_time – set the “low speed time” – the time that the transfer speed should be below the “low speed limit” for the library to consider it too slow and abort. See also CURLOPT_LOW_SPEED_TIME.
    • max_header_name_len – the maximal length of a header name. If a header name is bigger than this value, it is truncated to this length. The default value is 32.
    • follow_location – when the option is set to true (default) and the response has a 3xx code, the HTTP client will automatically issue another request to a location that a server sends in the Location header. If the new response is 3xx again, the HTTP client will issue still another request and so on in a loop until a non-3xx response will be received. This last response will be returned as a result. Setting this option to false allows to disable this behavior. In this case, the HTTP client will return a 3xx response itself.
    • no_proxy – a comma-separated list of hosts that do not require proxies, or ‘*’, or ‘’. Set no_proxy = host [, host ...] to specify hosts that can be reached without requiring a proxy, even if proxy has been set to a non-blank value and/or if a proxy-related environment variable has been set. Set no__proxy = '*' to specify that all hosts can be reached without requiring a proxy, which is equivalent to setting proxy=''. Set no_proxy = '' to specify that no hosts can be reached without requiring a proxy, even if a proxy-related environment variable (HTTP_PROXY) is used. If no_proxy is not set, then a proxy-related environment variable (HTTP_PROXY) may be used. See also CURLOPT_NOPROXY.
    • proxy - a proxy server host or IP address, or ‘’. If proxy is a host or IP address, then it may begin with a scheme, for example https:// for an https proxy or http:// for an http proxy. If proxy is set to ‘’ – an empty string, then proxy use is disabled, and no proxy-related environment variable will be used. If proxy is not set, then a proxy-related environment variable may be used, such as HTTP_PROXY or HTTPS_PROXY or FTP_PROXY, or ALL_PROXY if the protocol can be any protocol. See also CURLOPT_PROXY.
    • proxy_port – a proxy server port. The default is 443 for an https proxy and 1080 for a non-https proxy. See also CURLOPT_PROXYPORT.
    • proxy_user_pwd – a proxy server user name and/or password. Format: proxy_user_pwd = user_name: or proxy_user_pwd = :password or proxy_user_pwd = user_name:password. See also CURLOPT_USERPWD.
    • ssl_cert – path to a SSL client certificate file. See also CURLOPT_SSLCERT.
    • ssl_key – path to a private key file for a TLS and SSL client certificate. See also CURLOPT_SSLKEY.
    • timeout – number of seconds to wait for a curl API read request before timing out. The default timeout is set to infinity (36586400100 seconds).
    • unix_socket – a socket name to use instead of an Internet address, for a local connection. The Tarantool server must be built with libcurl 7.40 or later. See the second example later in this section.
    • verbose – set on/off verbose mode.
    • verify_host – set on/off verification of the certificate’s name (CN) against host. See also CURLOPT_SSL_VERIFYHOST.
    • verify_peer – set on/off verification of the peer’s SSL certificate. See also CURLOPT_SSL_VERIFYPEER.
    • accept_encoding – enables automatic decompression of HTTP responses by setting the contents of the Accept-Encoding: header sent in an HTTP request and enabling decoding of a response when the Content-Encoding: header is received. This option specifies what encoding to use. It can be an empty string which means the Accept-Encoding: header will contain all supported built-in encodings. Four encodings are supported: identity, meaning non-compressed, deflate which requests the server to compress its response using the zlib algorithm, gzip which requests the gzip algorithm and br which is brotli. Provide them in the string as a comma-separated list of accepted encodings, like: "br, gzip, deflate". For details of the option, refer to CURLOPT_ACCEPT_ENCODING.

connection information, with all of these components:

  • status – HTTP response status
  • reason – HTTP response status text
  • headers – a Lua table with normalized HTTP headers
  • body – response body
  • proto – protocol version


The cookies component contains a Lua table where the key is a cookie name. The value is an array of two elements where the first one is the cookie value and the second one is an array with the cookie’s options. Possible options are: “Expires”, “Max-Age”, “Domain”, “Path”, “Secure”, “HttpOnly”, “SameSite”. Note that an option is a string with ‘=’ splitting the option’s name and its value. Here you can find more info.


You can use cookies information like this:

tarantool> require('http.client').get('').cookies
- csrftoken:
  - bWJVkBybvX9LdJ8uLPOTVrit5P3VbRjE3potYVOuUnsSjYT5ahghDV06tXRkfnOl
  - - Max-Age=31449600
    - Path=/

tarantool> cookies = require('http.client').get('').cookies

tarantool> options = cookies['csrftoken'][2]

tarantool> for _, option in ipairs(options) do
         > if option:startswith('csrftoken cookie's Max-Age = ') then
         > print(option)
         > end
         > end

csrftoken cookie's Max-Age = 31449600


The following “shortcuts” exist for requests:

  • http_client:get(url, options) – shortcut for http_client:request("GET", url, nil, opts)
  • http_client:post (url, body, options) – shortcut for http_client:request("POST", url, body, opts)
  • http_client:put(url, body, options) – shortcut for http_client:request("PUT", url, body, opts)
  • http_client:patch(url, body, options) – shortcut for http_client:request("PATCH", url, body, opts)
  • http_client:options(url, options) – shortcut for http_client:request("OPTIONS", url, nil, opts)
  • http_client:head(url, options) – shortcut for http_client:request("HEAD", url, nil, opts)
  • http_client:delete(url, options) – shortcut for http_client:request("DELETE", url, nil, opts)
  • http_client:trace(url, options) – shortcut for http_client:request("TRACE", url, nil, opts)
  • http_client:connect(url, options) – shortcut for http_client:request("CONNECT", url, nil, opts)

Requests may be influenced by environment variables, for example users can set up an http proxy by setting HTTP_PROXY=proxy before initiating any requests, unless a proxy connection option has priority. See the web page document Environment variables libcurl understands.


The http_client:stat() function returns a table with statistics:

  • active_requests – number of currently executing requests
  • sockets_added – total number of sockets added into an event loop
  • sockets_deleted – total number of sockets sockets from an event loop
  • total_requests – total number of requests
  • http_200_responses – total number of requests which have returned code HTTP 200
  • http_other_responses – total number of requests which have not returned code HTTP 200
  • failed_requests – total number of requests which have failed including system errors, curl errors, and HTTP errors

Example 1:

Connect to an HTTP server, look at the size of the response for a ‘GET’ request, and look at the statistics for the session.

tarantool> http_client = require('http.client').new()
tarantool> r = http_client:request('GET','')
tarantool> string.len(r.body)
- 21725
tarantool> http_client:stat()
- total_requests: 1
  sockets_deleted: 2
  failed_requests: 0
  active_requests: 0
  http_other_responses: 0
  http_200_responses: 1
  sockets_added: 2

Example 2:

Start two Tarantool instances on the same computer.

On the first Tarantool instance, listen on a Unix socket:


On the second Tarantool instance, send via http_client:

http_client = require('http.client').new({5})
http_client:put('http://localhost/','body',{unix_socket = '/tmp/unix_domain_socket.sock'})

Terminal #1 will show an error message: “Invalid MsgPack”. This is not useful but demonstrates the syntax and demonstrates that was sent was received.

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