How to Do an Https Request With Erlang?

9 minutes read

To perform an HTTPS request in Erlang, you can follow these steps:

  1. First, make sure you have the required dependencies installed. Erlang's built-in SSL library is usually included in most distributions. If not, you may need to install it separately.
  2. Include the necessary libraries in your Erlang source file:
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%% Include the SSL and HTTP libraries
-include_lib("ssl/include/ssl.hrl").
-include_lib("inets/include/http.hrl").


  1. Start by setting up the SSL options for your request. This includes specifying the SSL version, ciphers, and other settings. You can customize these options based on your specific needs. Here's an example:
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%% SSL options for HTTPS request
ssl_opts() ->
    [{versions, ['tlsv1.2', 'tlsv1.3']},
     {ciphers, [{ecdhe_ecdsa, aes_256_gcm, sha384}]},
     {verify, verify_peer},
     {cacertfile, "path/to/ca_cert.pem"},
     {depth, 2}].


  1. Once you have the SSL options defined, you can proceed with making the HTTPS request. Use the httpc:request/4 function to send the request and obtain the response:
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make_https_request() ->
    {ok, RequestRef} = httpc:request(get,
                                    {"https://api.example.com", []},
                                    [], ssl_opts(), []),
    receive
        {http, {RequestRef, Result}} -> Result
    end.


  1. In the httpc:request/4 function, the first argument specifies the HTTP method (e.g., get, post, put, etc.), the second argument is the target URL in the form of {URL, Headers}, and the third argument contains additional request headers if needed.
  2. The ssl_opts() function is invoked as the fourth argument to provide the SSL options for the request. The empty list in the fifth argument represents optional request data like POST payload.
  3. Finally, receive the response using a selective receive block. The result will be returned once the response is received.


Remember to adapt the SSL options, URL, and other parameters according to your specific case. With these steps, you can successfully perform an HTTPS request in Erlang.

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What is the maximum number of simultaneous connections Erlang can handle for HTTPS requests?

The maximum number of simultaneous connections Erlang can handle for HTTPS requests depends on various factors such as the hardware, network configuration, and the Erlang distribution being used.


However, Erlang is known for its lightweight and scalable architecture, allowing it to handle a large number of concurrent connections efficiently. In practical scenarios, Erlang servers have been able to handle tens of thousands of simultaneous connections without significant performance degradation.


It's worth noting that tweaking various configuration parameters within Erlang, such as the maximum number of file descriptors and the size of the socket pool, can further optimize the system's ability to handle concurrent connections.


How to handle timeouts and retries in an HTTPS request with Erlang?

To handle timeouts and retries in an HTTPS request with Erlang, you can use the built-in libraries such as ssl and httpc. Here is an example of how you can implement it:

  1. Load the necessary libraries:
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-include_lib("ssl/include/ssl.hrl").
-include_lib("inets/include/http.hrl").

ssl:start().
httpc:start().


  1. Define a module to handle the HTTPS request:
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-module(https_request).
-export([request/5]).

request(Url, Method, Headers, Body, Retries) ->
    request(Url, Method, Headers, Body, Retries, []).
    
request(Url, Method, Headers, Body, Retries, PreviousError) ->
    case httpc:request(Method, {Url, Headers, "application/json", Body}, [], []) of
        {ok, {{_Version, 200, _StatusReason}, _Headers, Body}} ->
            {ok, Body};
        {error, Reason} ->
            case Retries of
                0 ->
                    {error, Reason, PreviousError};
                _ ->
                    request(Url, Method, Headers, Body, Retries - 1, [{Reason, erlang:now()} | PreviousError])
            end;
        _ ->
            {error, unknown}
    end.


  1. Add a function to handle timeouts:
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handle_timeout({_, _, _, Url, headers, _}, _Ref) ->
    {error, {timeout, Url}};
handle_timeout(_, Error) -> Error.


  1. Add a function to handle SSL errors:
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handle_ssl_alert({_, _, _, Url, headers, _}, Reason) ->
    {error, {ssl_error, Url, Reason}};
handle_ssl_alert(_, Error) -> Error.


  1. Configure the socket options for timeouts and retries:
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ssl_opts() ->
    [
        {cacertfile, "cacert.pem"},
        {verify, verify_peer},
        {socket_opts, [{
            recv_timeout, 5000,
            send_timeout, 5000,
            error_fun, fun handle_timeout/2,
            reconnect_after, 10000,
            ssl_alert_fun, fun handle_ssl_alert/2
        }]}
    ].


  1. Finally, make the HTTPS request with retries:
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-module(example).
-export([make_request/0]).

make_request() ->
    Url = "https://example.com/api",
    Method = post,
    Headers = [],
    Body = <<"{}">>,
    Retries = 3,
    
    https_request:request(Url, Method, Headers, Body, Retries).


This example includes a simple retry mechanism with a configurable number of retries. It also handles timeouts and SSL errors using the ssl and httpc libraries in Erlang. Remember to modify the ssl_opts() function according to your specific needs, such as specifying the CA certificate file, verification options, timeouts, and reconnect intervals.


What is the role of certificate revocation lists in an HTTPS request with Erlang?

In an HTTPS request with Erlang, certificate revocation lists (CRLs) play a crucial role in ensuring the validity and trustworthiness of the SSL/TLS certificates used in the communication. Here's an overview of their role:

  1. Verification of Certificate: During the HTTPS handshake, the server presents its SSL/TLS certificate to the client. The client needs to verify the authenticity and validity of this certificate. This verification process includes checking if the certificate has been revoked or compromised.
  2. CRL Distribution Points: The server's SSL/TLS certificate contains information about where the client can find the associated CRL. The CRL Distribution Points (CDPs) specify one or more locations (either URLs or file paths) where the client can access the revocation information.
  3. Retrieving CRLs: Upon receiving the server's certificate, the client extracts the CDP information from the certificate and fetches the CRL from the specified location(s). In Erlang, this involves making an HTTP request to the CRL URL or accessing the file at the given path.
  4. CRL Validation: Once retrieved, the CRL needs to be validated to ensure its integrity and authenticity. This involves checking the digital signature on the CRL using the issuer's public key and verifying that the CRL itself is not expired or revoked.
  5. Certificate Revocation Check: After validating the CRL, the client examines the CRL entries to determine if the server's certificate has been revoked. Each entry in the CRL represents a revoked certificate, and the client compares the server's certificate details with the entries to establish its revocation status.


If the server's certificate is found in the CRL, the client rejects the certificate, terminates the connection, and raises appropriate security-related alerts. On the other hand, if the certificate is not revoked or not found in the CRL, the client considers it valid and proceeds with establishing the secure connection.


Overall, CRLs in Erlang help maintain the trustworthiness of SSL/TLS certificates by providing an up-to-date mechanism for checking if a certificate has been revoked or compromised.


How to handle cookies in an HTTPS request using Erlang?

To handle cookies in an HTTPS request using Erlang, you can use the httpc module in the Erlang standard library. The httpc module provides functions for making HTTP requests and managing cookies.


Here is an example of how to handle cookies in an HTTPS request using Erlang:

  1. Start by including the inets and ssl modules in your Erlang code:
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%% Include necessary modules
-include_lib("inets/include/http.hrl").
-include_lib("ssl/include/ssl.hrl").


  1. Define a function to make the HTTPS request, handling the cookies in the process:
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-module(my_module).
-export([https_get/1]).

%% Make an HTTPS GET request with cookie handling
https_get(Url) ->
    %% Set up SSL options
    SslOptions = [{verify, verify_none}, {ciphers, [{ecdhe_ecdsa,aes_128_cbc,sha256}]}, {crl_check,false}],
    ssl:start(),
    inets:start(),

    %% Make the request
    httpc:request(get, {Url, []}, [], [{ssl, SslOptions}], fun handle_response/1).


%% Callback function to handle the response
handle_response({ok, {_Version, StatusCode, _ReasonPhrase}, Headers, Body}) ->
    %% Extract cookies from the response headers
    Cookies = proplists:get_all_values("set-cookie", Headers),

    %% Print the cookies
    io:format("Cookies: ~p~n", [Cookies]),

    %% Further processing of the response body
    process_body(Body).

%% Function to process the response body
process_body(Body) ->
    %% Do something with the response body
    io:format("Response Body: ~s~n", [Body]).


  1. Call the https_get/1 function with the URL you want to make the request to:
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%% Make an HTTPS GET request
my_module:https_get("https://example.com").


In this example, the https_get/1 function makes an HTTPS GET request to the specified URL. It sets up SSL options and uses the httpc:request/5 function to make the request. The response is handled by the handle_response/1 callback function, which extracts the cookies from the response headers and processes the response body.


Note: Make sure to include the SSL certificate verification and other necessary security measures in your production code to ensure a secure HTTPS request.

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