Programming language: Crystal
License: MIT License
Tags: HTTP    
Latest version: v0.10.7

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HTTP Requests with a chainable REST API, built-in sessions and middleware written by Crystal. Inspired from the awesome Ruby's HTTP/RESTClient and Python's requests.

Build in Crystal version >= v0.34.0, this document valid with latest commit.


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Add this to your application's shard.yml:

    github: icyleaf/halite


require "halite"

Making Requests

Make a GET request:

# Direct get url

# Support NamedTuple as query params
Halite.get("http://httpbin.org/get", params: {
  language: "crystal",
  shard: "halite"

# Also support Hash as query params
Halite.get("http://httpbin.org/get", headers: {
    "Private-Token" => "T0k3n"
  }, params: {
    "language" => "crystal",
    "shard" => "halite"

# And support chainable
Halite.header(private_token: "T0k3n")
      .get("http://httpbin.org/get", params: {
        "language" => "crystal",
        "shard" => "halite"

See also all chainable methods.

Many other HTTP methods are available as well:

  • get
  • head
  • post
  • put
  • delete
  • patch
  • options

Passing Parameters

Query string parameters

Use the params argument to add query string parameters to requests:

Halite.get("http://httpbin.org/get", params: { "firstname" => "Olen", "lastname" => "Rosenbaum" })
Form data

Use the form argument to pass data serialized as form encoded:

Halite.post("http://httpbin.org/post", form: { "firstname" => "Olen", "lastname" => "Rosenbaum" })
File uploads (via form data)

To upload files as if form data, construct the form as follows:

Halite.post("http://httpbin.org/post", form: {
  "username" => "Quincy",
  "avatar" => File.open("/Users/icyleaf/quincy_avatar.png")

It is possible to upload multiple files:

Halite.post("http://httpbin.org/post", form: {
  photos: [
  album_name: "samples"

Or pass the name with []:

Halite.post("http://httpbin.org/post", form: {
  "photos[]" => [
  "album_name" => "samples"

Multiple files can also be uploaded using both ways above, it depend on web server.

JSON data

Use the json argument to pass data serialized as body encoded:

Halite.post("http://httpbin.org/post", json: { "firstname" => "Olen", "lastname" => "Rosenbaum" })
Raw String

Use the raw argument to pass raw string as body and set the Content-Type manually:

# Set content-type to "text/plain" by default
Halite.post("http://httpbin.org/post", raw: "name=Peter+Lee&address=%23123+Happy+Ave&language=C%2B%2B")

# Set content-type manually
  headers: {
    "content-type" => "application/json"
  raw: %Q{{"name":"Peter Lee","address":"23123 Happy Ave","language":"C++"}}

Passing advanced options


Use the #basic_auth method to perform HTTP Basic Authentication using a username and password:

Halite.basic_auth(user: "user", pass: "p@ss").get("http://httpbin.org/get")

# We can pass a raw authorization header using the auth method:
Halite.auth("Bearer dXNlcjpwQHNz").get("http://httpbin.org/get")
User Agent

Use the #user_agent method to overwrite default one:

Halite.user_agent("Crystal Client").get("http://httpbin.org/user-agent")

Here are two way to passing headers data:

1. Use the #headers method
Halite.headers(private_token: "T0k3n").get("http://httpbin.org/get")

# Also support Hash or NamedTuple
Halite.headers({ "private_token" => "T0k3n" }).get("http://httpbin.org/get")

# Or
Halite.headers({ private_token: "T0k3n" }).get("http://httpbin.org/get")
2. Use the headers argument in the available request method:
Halite.get("http://httpbin.org/anything" , headers: { private_token: "T0k3n" })

Halite.post("http://httpbin.org/anything" , headers: { private_token: "T0k3n" })
Passing cookies in requests

The Halite.cookies option can be used to configure cookies for a given request:

Halite.cookies(session_cookie: "6abaef100b77808ceb7fe26a3bcff1d0")
Get cookies in requests

To obtain the cookies(cookie jar) for a given response, call the #cookies method:

r = Halite.get("http://httpbin.org/cookies?set?session_cookie=6abaef100b77808ceb7fe26a3bcff1d0")
pp r.cookies
# => #<HTTP::Cookies:0x10dbed980 @cookies={"session_cookie" =>#<HTTP::Cookie:0x10ec20f00 @domain=nil, @expires=nil, @extension=nil, @http_only=false, @name="session_cookie", @path="/", @secure=false, @value="6abaef100b77808ceb7fe26a3bcff1d0">}>
Redirects and History
Automatically following redirects

The Halite.follow method can be used for automatically following redirects(Max up to 5 times):

# Set the cookie and redirect to http://httpbin.org/cookies
Limiting number of redirects

As above, set over 5 times, it will raise a Halite::TooManyRedirectsError, but you can change less if you can:

Disabling unsafe redirects

It only redirects with GET, HEAD request and returns a 300, 301, 302 by default, otherwise it will raise a Halite::StateError. We can disable it to set :strict to false if we want any method(verb) requests, in which case the GET method(verb) will be used for that redirect:

Halite.follow(strict: false)

Response#history property list contains the Response objects that were created in order to complete the request. The list is ordered from the oldest to most recent response.

r = Halite.follow

# => http://httpbin.org/get

# => 200

# => [
#      #<Halite::Response HTTP/1.1 302 FOUND {"Location" => "/relative-redirect/2" ...>,
#      #<Halite::Response HTTP/1.1 302 FOUND {"Location" => "/relative-redirect/1" ...>,
#      #<Halite::Response HTTP/1.1 302 FOUND {"Location" => "/get" ...>,
#      #<Halite::Response HTTP/1.1 200 OK    {"Content-Type" => "application/json" ...>
#    ]

NOTE: It contains the Response object if you use history and HTTP was not a 30x, For example:

r = Halite.get("http://httpbin.org/get")
r.history.size # => 0

r = Halite.follow
r.history.size # => 1

By default, the Halite does not enforce timeout on a request. We can enable per operation timeouts by configuring them through the chaining API.

The connect timeout is the number of seconds Halite will wait for our client to establish a connection to a remote server call on the socket.

Once our client has connected to the server and sent the HTTP request, the read timeout is the number of seconds the client will wait for the server to send a response.

# Separate set connect and read timeout
Halite.timeout(connect: 3.0, read: 2.minutes)

# Boath set connect and read timeout
# The timeout value will be applied to both the connect and the read timeouts.


The Halite supports HTTPS via Crystal's built-in OpenSSL module. All you have to do in order to use HTTPS is pass in an https://-prefixed URL.

To use client certificates, you can pass in a custom OpenSSL::SSL::Context::Client object containing the certificates you wish to use:

tls = OpenSSL::SSL::Context::Client.new
tls.ca_certificates = File.expand_path("~/client.crt")
tls.private_key = File.expand_path("~/client.key")

Halite.get("https://httpbin.org/anything", tls: tls)

Response Handling

After an HTTP request, Halite::Response object have several useful methods. (Also see the API documentation).

  • #body: The response body.
  • #body_io: The response body io only available in streaming requests.
  • #status_code: The HTTP status code.
  • #content_type: The content type of the response.
  • #content_length: The content length of the response.
  • #cookies: A HTTP::Cookies set by server.
  • #headers: A HTTP::Headers of the response.
  • #links: A list of Halite::HeaderLink set from headers.
  • #parse: (return value depends on MIME type) parse the body using a parser defined for the #content_type.
  • #to_a: Return a Hash of status code, response headers and body as a string.
  • #to_raw: Return a raw of response as a string.
  • #to_s: Return response body as a string.
  • #version: The HTTP version.
Response Content

We can read the content of the server's response by call #body:

r = Halite.get("http://httpbin.org/user-agent")
# => {"user-agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.87 Safari/537.36"}

The gzip and deflate transfer-encodings are automatically decoded for you. And requests will automatically decode content from the server. Most unicode charsets are seamlessly decoded.

JSON Content

There’s also a built-in a JSON adapter, in case you’re dealing with JSON data:

r = Halite.get("http://httpbin.org/user-agent")
r.parse # simplily by default
# => {
# =>   "user-agent" => "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.87 Safari/537.36"
# => }
Parsing Content

Halite::Response has a MIME type adapter system that you can use a decoder to parse the content, we can inherit Halite::MimeTypes::Adapter to make our adapter:

# Define a MIME type adapter
class YAMLAdapter < Halite::MimeType::Adapter
  def decode(string)

  def encode(obj)

# Register to Halite to invoke
Halite::MimeType.register YAMLAdapter.new, "application/x-yaml", "yaml", "yml"

# Test it!
r = Halite.get "https://raw.githubusercontent.com/icyleaf/halite/master/shard.yml"
r.parse("yaml") # or "yml"
# => {"name" => "halite", "version" => "0.4.0", "authors" => ["icyleaf <[email protected]>"], "crystal" => "0.25.0", "license" => "MIT"}
Binary Data

Store binary data (eg, application/octet-stream) to file, you can use streaming requests:

Halite.get("https://github.com/icyleaf/halite/archive/master.zip") do |response|
  filename = response.filename || "halite-master.zip"
  File.open(filename, "w") do |file|
    IO.copy(response.body_io, file)

Error Handling

  • For any status code, a Halite::Response will be returned.
  • If request timeout, a Halite::TimeoutError will be raised.
  • If a request exceeds the configured number of maximum redirections, a Halite::TooManyRedirectsError will raised.
  • If request uri is http and configured tls context, a Halite::RequestError will raised.
  • If request uri is invalid, a Halite::ConnectionError/Halite::UnsupportedMethodError/Halite::UnsupportedSchemeError will raised.
Raise for status code

If we made a bad request(a 4xx client error or a 5xx server error response), we can raise with Halite::Response.raise_for_status.

But, since our status_code was not 4xx or 5xx, it returns nil when we call it:

urls = [

urls.each do |url|
  r = Halite.get url
    p r.body
  rescue ex : Halite::ClientError | Halite::ServerError
    p "[#{ex.status_code}] #{ex.status_message} (#{ex.class})"

# => "[404] not found error with url: https://httpbin.org/status/404  (Halite::ClientError)"
# => "[500] internal server error error with url: https://httpbin.org/status/500?foo=bar  (Halite::ServerError)"
# => ""


Halite now has middleware (a.k.a features) support providing a simple way to plug in intermediate custom logic in your HTTP client, allowing you to monitor outgoing requests, incoming responses, and use it as an interceptor.

Available features:

  • Logging (Yes, logging is based on feature, cool, aha!)
  • Local Cache (local storage, speed up in development)

Write a simple feature

Let's implement simple middleware that prints each request:

class RequestMonister < Halite::Feature
  @label : String
  def initialize(**options)
    @label = options.fetch(:label, "")

  def request(request) : Halite::Request
    puts @label
    puts request.verb
    puts request.uri
    puts request.body


  Halite.register_feature "request_monster", self

Then use it in Halite:

Halite.use("request_monster", label: "testing")
      .post("http://httpbin.org/post", form: {name: "foo"})

# Or configure to client
client = Halite::Client.new do
  use "request_monster", label: "testing"

client.post("http://httpbin.org/post", form: {name: "foo"})

# => testing
# => POST
# => http://httpbin.org/post
# => name=foo

Write a interceptor

Halite's killer feature is the interceptor, Use Halite::Feature::Chain to process with two result:

  • next: perform and run next interceptor
  • return: perform and return

So, you can intercept and turn to the following registered features.

class AlwaysNotFound < Halite::Feature
  def intercept(chain)
    response = chain.perform
    response = Halite::Response.new(chain.request.uri, 404, response.body, response.headers)

  Halite.register_feature "404", self

class PoweredBy < Halite::Feature
  def intercept(chain)
    if response = chain.response
      response.headers["X-Powered-By"] = "Halite"

  Halite.register_feature "powered_by", self

r = Halite.use("404").use("powered_by").get("http://httpbin.org/user-agent")
r.status_code               # => 404
r.headers["X-Powered-By"]   # => Halite
r.body                      # => {"user-agent":"Halite/0.6.0"}

For more implementation details about the feature layer, see the Feature class and examples and specs.

Advanced Usage


Halite provides a traditional way to instance client, and you can configure any chainable methods with block:

client = Halite::Client.new do
  # Set basic auth
  basic_auth "username", "password"

  # Enable logging
  logging true

  # Set timeout
  timeout 10.seconds

  # Set user agent
  headers user_agent: "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.94 Safari/537.36"

# You also can configure in this way

r = client.get("http://httpbin.org/get")


No more given endpoint per request, use endpoint will make the request URI shorter, you can set it in flexible way:

client = Halite::Client.new do
  endpoint "https://gitlab.org/api/v4"
  user_agent "Halite"

client.get("users")       # GET https://gitlab.org/api/v4/users

# You can override the path by using an absolute path
client.get("/users")      # GET https://gitlab.org/users


As like requests.Session(), Halite built-in session by default.

Let's persist some cookies across requests:

client = Halite::Client.new
# => 2018-06-25 18:41:05 +08:00 | request | GET    | http://httpbin.org/cookies/set?private_token=6abaef100b77808ceb7fe26a3bcff1d0
# => 2018-06-25 18:41:06 +08:00 | response | 302    | http://httpbin.org/cookies/set?private_token=6abaef100b77808ceb7fe26a3bcff1d0 | text/html
# => <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
# => <title>Redirecting...</title>
# => <h1>Redirecting...</h1>
# => <p>You should be redirected automatically to target URL: <a href="/cookies">/cookies</a>.  If not click the link.
# => 2018-06-25 18:41:06 +08:00 | request | GET    | http://httpbin.org/cookies
# => 2018-06-25 18:41:07 +08:00 | response | 200    | http://httpbin.org/cookies | application/json
# => {"cookies":{"private_token":"6abaef100b77808ceb7fe26a3bcff1d0"}}

All it support with chainable methods in the other examples list in requests.Session.

Note, however, that chainable methods will not be persisted across requests, even if using a session. This example will only send the cookies or headers with the first request, but not the second:

client = Halite::Client.new
r = client.cookies("username": "foobar").get("http://httpbin.org/cookies")
r.body # => {"cookies":{"username":"foobar"}}

r = client.get("http://httpbin.org/cookies")
r.body # => {"cookies":{}}

If you want to manually add cookies, headers (even features etc) to your session, use the methods start with `with_` in `Halite::Options`
to manipulate them:

r = client.get("http://httpbin.org/cookies")
r.body # => {"cookies":{}}

client.options.with_cookie("username": "foobar")
r = client.get("http://httpbin.org/cookies")
r.body # => {"cookies":{"username":"foobar"}}

Streaming Requests

Similar to HTTP::Client (search keyword "Streaming") usage with a block, you can easily use same way, but Halite returns a Halite::Response object:

r = Halite.get("http://httpbin.org/stream/5") do |response|
  response.status_code                  # => 200
  response.body_io.each_line do |line|
    puts JSON.parse(line)               # => {"url" => "http://httpbin.org/stream/5", "args" => {}, "headers" => {"Host" => "httpbin.org", "Connection" => "close", "User-Agent" => "Halite/0.8.0", "Accept" => "*/*", "Accept-Encoding" => "gzip, deflate"}, "id" => 0_i64}


body_io is avaiabled as an IO and not reentrant safe. Might throws a "Nil assertion failed" exception if there is no data in the IO (such like head requests). Calling this method multiple times causes some of the received data being lost.

One more thing, use streaming requests the response will always enable redirect automatically.


Halite does not enable logging on each request and response too. We can enable per operation logging by configuring them through the chaining API.

By default, Halite will logging all outgoing HTTP requests and their responses(without binary stream) to STDOUT on DEBUG level. You can configuring the following options:

  • logging: Instance your Halite::Logging::Abstract, check Use the custom logging.
  • format: Output format, built-in common and json, you can write your own.
  • file: Write to file with path, works with format.
  • filemode: Write file mode, works with format, by default is a. (append to bottom, create it if file is not exist)
  • skip_request_body: By default is false.
  • skip_response_body: By default is false.
  • skip_benchmark: Display elapsed time, by default is false.
  • colorize: Enable colorize in terminal, only apply in common format, by default is true.

NOTE: format (file and filemode) and logging are conflict, you can not use both.

Let's try with it:

# Logging json request
      .get("http://httpbin.org/get", params: {name: "foobar"})

# => 2018-06-25 18:33:14 +08:00 | request  | GET    | http://httpbin.org/get?name=foobar
# => 2018-06-25 18:33:15 +08:00 | response | 200    | http://httpbin.org/get?name=foobar | 381.32ms | application/json
# => {"args":{"name":"foobar"},"headers":{"Accept":"*/*","Accept-Encoding":"gzip, deflate","Connection":"close","Host":"httpbin.org","User-Agent":"Halite/0.3.2"},"origin":"","url":"http://httpbin.org/get?name=foobar"}

# Logging image request

# => 2018-06-25 18:34:15 +08:00 | request  | GET    | http://httpbin.org/image/png
# => 2018-06-25 18:34:15 +08:00 | response | 200    | http://httpbin.org/image/png | image/png

# Logging with options
Halite.logging(skip_request_body: true, skip_response_body: true)
      .post("http://httpbin.org/get", form: {image: File.open("halite-logo.png")})

# => 2018-08-28 14:33:19 +08:00 | request  | POST   | http://httpbin.org/post
# => 2018-08-28 14:33:21 +08:00 | response | 200    | http://httpbin.org/post | 1.61s | application/json
JSON-formatted logging

It has JSON formatted for developer friendly logging.

Halite.logging(format: "json")
      .get("http://httpbin.org/get", params: {name: "foobar"})
Write to a log file
# Write plain text to a log file
Halite.logging(file: "logs/halite.log", skip_benchmark: true, colorize: false)
      .get("http://httpbin.org/get", params: {name: "foobar"})

# Write json data to a log file
Halite.logging(format: "json", file: "logs/halite.log")
      .get("http://httpbin.org/get", params: {name: "foobar"})
Use the custom logging

Creating the custom logging by integration Halite::Logging::Abstract abstract class. Here has two methods must be implement: #request and #response.

class CustomLogging < Halite::Logging::Abstract
  def request(request)
    @logger.info { "| >> | %s | %s %s" % [request.verb, request.uri, request.body] }

  def response(response)
    @logger.info { "| << | %s | %s %s" % [response.status_code, response.uri, response.content_type] }

# Add to adapter list (optional)
Halite::Logging.register "custom", CustomLogging.new

Halite.logging(logging: CustomLogging.new)
      .get("http://httpbin.org/get", params: {name: "foobar"})

# We can also call it use format name if you added it.
Halite.logging(format: "custom")
      .get("http://httpbin.org/get", params: {name: "foobar"})

# => 2017-12-13 16:40:13 +08:00 | >> | GET | http://httpbin.org/get?name=foobar
# => 2017-12-13 16:40:15 +08:00 | << | 200 | http://httpbin.org/get?name=foobar application/json

Local Cache

Local cache feature is caching responses easily with Halite through an chainable method that is simple and elegant yet powerful. Its aim is to focus on the HTTP part of caching and do not worrying about how stuff stored, api rate limiting even works without network(offline).

It has the following options:

  • file: Load cache from file. it conflict with path and expires.
  • path: The path of cache, default is "/tmp/halite/cache/"
  • expires: The expires time of cache, default is never expires.
  • debug: The debug mode of cache, default is true

With debug mode, cached response it always included some headers information:

  • X-Halite-Cached-From: Cache source (cache or file)
  • X-Halite-Cached-Key: Cache key with verb, uri and body (return with cache, not file passed)
  • X-Halite-Cached-At: Cache created time
  • X-Halite-Cached-Expires-At: Cache expired time (return with cache, not file passed)
Halite.use("cache").get "http://httpbin.org/anything"     # request a HTTP
r = Halite.use("cache").get "http://httpbin.org/anything" # request from local storage
r.headers                                                 # => {..., "X-Halite-Cached-At" => "2018-08-30 10:41:14 UTC", "X-Halite-Cached-By" => "Halite", "X-Halite-Cached-Expires-At" => "2018-08-30 10:41:19 UTC", "X-Halite-Cached-Key" => "2bb155e6c8c47627da3d91834eb4249a"}}

Link Headers

Many HTTP APIs feature Link headers. GitHub uses these for pagination in their API, for example:

r = Halite.get "https://api.github.com/users/icyleaf/repos?page=1&per_page=2"
# => {"next" =>
# =>   Halite::HeaderLink(
# =>    @params={},
# =>    @rel="next",
# =>    @target="https://api.github.com/user/17814/repos?page=2&per_page=2"),
# =>  "last" =>
# =>   Halite::HeaderLink(
# =>    @params={},
# =>    @rel="last",
# =>    @target="https://api.github.com/user/17814/repos?page=41&per_page=2")}

# => "https://api.github.com/user/17814/repos?page=2&per_page=2"

# => {}

Help and Discussion

You can browse the API documents:


You can browse the all chainable methods:


You can browse the Changelog:


If you have found a bug, please create a issue here:



Halite is a open source, collaboratively funded project. If you run a business and are using Halite in a revenue-generating product, it would make business sense to sponsor Halite development. Individual users are also welcome to make a one time donation if Halite has helped you in your work or personal projects.

You can donate via Paypal.

How to Contribute

Your contributions are always welcome! Please submit a pull request or create an issue to add a new question, bug or feature to the list.

All Contributors are on the wall.

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MIT License © icyleaf

*Note that all licence references and agreements mentioned in the halite README section above are relevant to that project's source code only.