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diff --git a/README.md b/README.md
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--- a/README.md
+++ b/README.md
@@ -1,247 +1,248 @@
# Tesla
[![CircleCI Status](https://circleci.com/gh/teamon/tesla.png?style=shield)](https://circleci.com/gh/teamon/tesla)
[![Hex.pm](https://img.shields.io/hexpm/v/tesla.svg)](http://hex.pm/packages/tesla)
Tesla is an HTTP client losely based on [Faraday](https://github.com/lostisland/faraday).
It embraces the concept of middleware when processing the request/response cycle.
## Direct usage
```ex
# Example get request
response = Tesla.get("http://httpbin.org/ip")
response.status # => 200
response.body # => '{\n "origin": "87.205.72.203"\n}\n'
response.headers # => %{'Content-Type' => 'application/json' ...}
response = Tesla.get("http://httpbin.org/get", query: [a: 1, b: "foo"])
response.url # => "http://httpbin.org/get?a=1&b=foo"
# Example post request
response = Tesla.post("http://httpbin.org/post", "data", headers: %{"Content-Type" => "application/json"})
```
## Installation
Add `tesla` as dependency in `mix.exs`
```ex
defp deps do
[{:tesla, "~> 0.5.0"},
{:poison, ">= 1.0.0"}] # for JSON middleware
end
```
When using `ibrowse` or `hackney` adapters remember to alter applications list in `mix.exs`
```ex
def application do
[applications: [:ibrowse, ...], ...] # or :hackney
end
```
## Creating API clients
Use `Tesla` module to create API wrappers.
For example
```ex
defmodule GitHub do
use Tesla
plug Tesla.Middleware.BaseUrl, "https://api.github.com"
plug Tesla.Middleware.Headers, %{'Authorization' => 'xyz'}
plug Tesla.Middleware.JSON
adapter Tesla.Adapter.Hackney
def user_repos(login) do
get("/user/" <> login <> "/repos")
end
end
```
Then use it like this:
```ex
GitHub.get("/user/teamon/repos")
GitHub.user_repos("teamon")
```
## Adapters
Tesla has support for different adapters that do the actual HTTP request processing.
### [httpc](http://erlang.org/doc/man/httpc.html)
The default adapter, available in all erlang installations
### [hackney](https://github.com/benoitc/hackney)
This adapter supports real streaming body.
To use it simply include `adapter :hackney` line in your API client definition.
NOTE: Remember to include hackney in applications list.
### [ibrowse](https://github.com/cmullaparthi/ibrowse)
Tesla has built-in support for [ibrowse](https://github.com/cmullaparthi/ibrowse) Erlang HTTP client.
To use it simply include `adapter :ibrowse` line in your API client definition.
NOTE: Remember to include ibrowse in applications list.
### Test / Mock
When testing it might be useful to use simple function as adapter:
```ex
defmodule MyApi do
use Tesla
adapter fn (env) ->
case env.url do
"/" -> %{env | status: 200, body: "home"}
"/about" -> %{env | status: 200, body: "about us"}
end
end
end
```
## Middleware
### Basic
- `Tesla.Middleware.BaseUrl` - set base url for all request
- `Tesla.Middleware.Headers` - set request headers
- `Tesla.Middleware.Query` - set query parameters
- `Tesla.Middleware.DecodeRels` - decode `Link` header into `opts[:rels]` field in response
+- `Tesla.Middleware.Retry` - retry few times in case of connection refused
### JSON
NOTE: requires [poison](https://hex.pm/packages/poison) (or other engine) as dependency
- `Tesla.Middleware.JSON`` - encode/decode request/response bodies as JSON
If you are using different json library it can be easily configured:
```ex
plug Tesla.Middleware.JSON, engine: JSX, engine_opts: [strict: [:comments]]
# or
plug Tesla.Middleware.JSON, decode: &JSX.decode/1, encode: &JSX.encode/1
```
See [`json.ex`](https://github.com/teamon/tesla/blob/master/lib/tesla/middleware/json.ex) for implementation details.
### Logging
- `Tesla.Middleware.Logger` - log each request in single line including method, path, status and execution time (colored)
- `Tesla.Middleware.DebugLogger` - log full request and response (incl. headers and body)
## Dynamic middleware
All methods can take a middleware function as the first parameter.
This allow to use convenient syntax for modifying the behaviour in runtime.
Consider the following case: GitHub API can be accessed using OAuth token authorization.
We can't use `plug Tesla.Middleware.Headers, %{"Authorization" => "token here"}` since this would be compiled only once and there is no way to insert dynamic user token.
Instead, we can use `Tesla.build_client` to create a dynamic middleware function:
```ex
defmodule GitHub do
# same as above
def client(token) do
Tesla.build_client [
{Tesla.Middleware.Headers, %{"Authorization" => "token: " <> token }}
]
end
end
```
and then:
```ex
client = GitHub.client(user_token)
client |> GitHub.user_repos("teamon")
client |> GitHub.get("/me")
```
## Writing your own middleware
A Tesla middleware is a module with `call/3` function, that at some point calls `Tesla.run(env, next)` to process
the rest of stack
```ex
defmodule MyMiddleware do
def call(env, next, options) do
env
|> do_something_with_request
|> Tesla.run(next)
|> do_something_with_response
end
end
```
The arguments are:
- `env` - `Tesla.Env` instance
- `next` - middleware continuation stack; to be executed with `Tesla.run(env, next)`
- `options` - arguments passed during middleware configuration (`plug MyMiddleware, options`)
There is no distinction between request and response middleware, it's all about executing `Tesla.run/2` function at the correct time.
For example, z request logger middleware could be implemented like this:
```ex
defmodule Tesla.Middleware.RequestLogger do
def call(env, next, _) do
IO.inspect env # print request env
Tesla.run(env, next)
end
end
```
and response logger middleware like this:
```ex
defmodule Tesla.Middleware.ResponseLogger do
def call(env, next, _) do
res = Tesla.run(env, next)
IO.inspect res # print response env
res
end
end
```
See [`core.ex`](https://github.com/teamon/tesla/blob/master/lib/tesla/middleware/core.ex) and [`json.ex`](https://github.com/teamon/tesla/blob/master/lib/tesla/middleware/json.ex) for more examples.
## Streaming body
If adapter supports it, you can pass a [Stream](http://elixir-lang.org/docs/stable/elixir/Stream.html) as body, e.g.:
```ex
defmodule ES do
use Tesla.Builder
plug Tesla.Middleware.BaseUrl, "http://localhost:9200"
plug Tesla.Middleware.DecodeJson
plug Tesla.Middleware.EncodeJson
def index(records) do
stream = records |> Stream.map(fn record -> %{index: [some, data]})
post("/_bulk", stream)
end
end
```
Each piece of stream will be encoded as json and sent as a new line (conforming to json stream format)
diff --git a/lib/tesla/middleware/retry.ex b/lib/tesla/middleware/retry.ex
new file mode 100644
index 0000000..90f251a
--- /dev/null
+++ b/lib/tesla/middleware/retry.ex
@@ -0,0 +1,46 @@
+defmodule Tesla.Middleware.Retry do
+ @moduledoc """
+ Retry few times in case of connection refused error.
+
+ Example:
+ defmodule MyClient do
+ use Tesla
+
+ plug Tesla.Middleware.Retry, delay: 500, max_retries: 10
+ end
+
+ Options:
+ - `:delay` - number of milisecond to wait before retrying (defaults to 1000)
+ - `:max_retries` - maximum number of retries (defaults to 5)
+ """
+
+ @defaults [
+ delay: 1000,
+ max_retries: 5
+ ]
+
+ def call(env, next, opts) do
+ opts = opts || []
+ delay = Keyword.get(opts, :delay, @defaults[:delay])
+ max_retries = Keyword.get(opts, :max_retries, @defaults[:max_retries])
+
+ retry(env, next, delay, max_retries)
+ end
+
+ defp retry(env, next, _delay, retries) when retries <= 1 do
+ Tesla.run(env, next)
+ end
+
+ defp retry(env, next, delay, retries) do
+ Tesla.run(env, next)
+ rescue
+ error -> case error do
+ %Tesla.Error{reason: :econnrefused} ->
+ :timer.sleep(delay)
+ retry(env, next, delay, retries - 1)
+
+ _ ->
+ reraise error, System.stacktrace
+ end
+ end
+end
diff --git a/test/tesla/middleware/retry_test.exs b/test/tesla/middleware/retry_test.exs
new file mode 100644
index 0000000..5fcf3a4
--- /dev/null
+++ b/test/tesla/middleware/retry_test.exs
@@ -0,0 +1,49 @@
+defmodule RetryTest do
+ use ExUnit.Case, async: false
+
+ use Tesla.Middleware.TestCase, middleware: Tesla.Middleware.Retry
+
+ defmodule LaggyAdapter do
+ def start_link, do: Agent.start_link(fn -> 0 end, name: __MODULE__)
+
+ def call(env, _opts) do
+ Agent.get_and_update __MODULE__, fn retries ->
+ response = case env.url do
+ "/ok" -> env
+ "/maybe" when retries < 5 -> {:error, :econnrefused}
+ "/maybe" -> env
+ "/nope" -> {:error, :econnrefused}
+ end
+
+ {response, retries + 1}
+ end
+ end
+ end
+
+
+ defmodule Client do
+ use Tesla
+
+ plug Tesla.Middleware.Retry, delay: 10, max_retries: 10
+
+ adapter LaggyAdapter
+ end
+
+ setup do
+ {:ok, _} = LaggyAdapter.start_link
+ :ok
+ end
+
+ test "pass on successful request" do
+ assert %Tesla.Env{url: "/ok", method: :get} == Client.get("/ok")
+ end
+
+ test "finally pass on laggy request" do
+ assert %Tesla.Env{url: "/maybe", method: :get} == Client.get("/maybe")
+ end
+
+ test "raise if max_retries is exceeded" do
+ assert_raise Tesla.Error, fn -> Client.get("/nope") end
+ end
+
+end

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