# MaxwellCache
[](https://travis-ci.org/milkwine/maxwell_cache)
Maxwell middleware to cache success response. Backend by [Cachex](https://github.com/whitfin/cachex).
## Installation
Add `maxwell_cache` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[
{:maxwell_cache, ~> 0.1.0"},
]
end
```
## Usage
More `Maxwell` usage could be seen [here](https://github.com/zhongwencool/maxwell).
Short usage of this middleware here:
```elixir
#Set Maxwell Middleware.
middleware Maxwell.Middleware.Cache, ttl: :timer.minutes(1), namespace: "httpbin"
# Import middleware method.
import Maxwell.Middleware.Cache, only: [from_cache: 1, from_source: 1, set_ttl: 2]
# Middleware is doing nothing.
def get_uuid do
"/uuid"
|> new()
|> get!
|> get_resp_body
end
# Set to requrest from real remote server and set cache if response success.
def get_uuid_from_source do
"/uuid"
|> new()
|> from_source()
|> get!
|> get_resp_body
end
# Set to get response from cache first and set ttl. Request real remote server if cache not found.
def get_uuid_from_cache do
"/uuid"
|> new()
|> from_cache()
|> set_ttl(:timer.seconds(5))
|> get!
|> get_resp_body
end
```
## Options
### Cache key relate to request
Cache key is consist of two parts, middleware `namespace` and information generated by `hash_func/1`.
Default `hash_func/1` is below:
```elixir
def default_hash_func(%Maxwell.Conn{} = conn) do
query_string = conn.query_string |> Maxwell.Query.encode
headers = conn.req_headers |> Maxwell.Query.encode
body = conn.req_body |> :erlang.phash2
"#{conn.method}|#{conn.url}|#{conn.path}|#{query_string}|#{headers}|#{body}"
end
```
Both of them could be set by middleware `init/1`.
```elixir
middleware Maxwell.Middleware.Cache, namespace: "yournamespace", hash_func: &your_hash_func/1
```
### Cache limit
Default `Cachex limit` is `%Cachex.Limit{limit: 2000, reclaim: 0.1}`, could be change in `config.exs`:
```elixir
config :maxwell_cache, limit: %Cachex.Limit{limit: 2000, reclaim: 0.1}
```
More information could be seen [cachex doc](https://hexdocs.pm/cachex/readme.html#cache-limits).
### Cache ttl
Default ttl is `:timer.seconds(10)`, this could be change in `config.exs`:
```elixir
config :maxwell_cache, default_ttl: :timer.seconds(10)
```
Client moudle could have their own ttl:
```elixir
middleware Maxwell.Middleware.Cache, ttl: :timer.seconds(10)
```
Request could set ttl by using `set_ttl/1`:
```elixir
def get_uuid_from_cache do
"/uuid"
|> new()
|> from_cache()
|> set_ttl(:timer.seconds(5))
|> get!
|> get_resp_body
end
```
