Using Faraday HTTP Cache (or just using Faraday middleware)

[jagregory]

I'm trying to use faraday-http-cache with Hyperclient, but it isn't proving easy.

faraday-http-cache expects to sit before :net_http in the middleware stack. A working example from their docs looks like this:

client = Faraday.new('https://api.github.com') do |stack|
  stack.response :json, content_type: /\bjson$/
  stack.use :http_cache, logger: ActiveSupport::Logger.new(STDOUT)
  stack.adapter Faraday.default_adapter
end

# which has this middleware:
[FaradayMiddleware::ParseJson, Faraday::HttpCache, Faraday::Adapter::NetHttp]

However, trying to achieve the same thing in Hyperclient doesn't work as expected. The following setup, which I would expect to work, results in duplicate :net_http in the middleware.

client = Hyperclient.new('https://api.github.com')
client.connection.use :http_cache, logger: ActiveSupport::Logger.new(STDOUT)
client.connection.adapter Faraday.default_adapter

# which has this middleware (see the duplicate NetHttp):
[FaradayMiddleware::EncodeJson, FaradayMiddleware::ParseJson, Faraday::Adapter::NetHttp, Faraday::HttpCache, Faraday::Adapter::NetHttp]

This is because of the way Hyperclient initialises the Faraday connection (see default_faraday_block) with the :net_http adapter when it creates the connection.

The only way I've got this working was by monkey patching or subclassing EntryPoint and overriding the default_faraday_block so the :http_cache middleware is inserted before :net_http.

class Hyperclient::EntryPoint
  def default_faraday_block
    lambda do |faraday|
      faraday.request  :json
      faraday.response :json, content_type: /\bjson$/
      faraday.use :http_cache, logger: ActiveSupport::Logger.new(STDOUT)
      faraday.adapter :net_http
    end
  end
end

Advice? This is less than ideal.

[oriolgual]

I'm not sure if it will work, but what happens if you use insert_after or 'insert_before ?

client = Hyperclient.new('https://api.github.com')
client.connection.insert_after :json, :http_cache, logger: ActiveSupport::Logger.new(STDOUT)

Or

client = Hyperclient.new('https://api.github.com')
client.connection.insert_before Faraday::Adapter::NetHttp, :http_cache, logger: ActiveSupport::Logger.new(STDOUT)

[jagregory]

Thanks, insert_before seems to do the trick, except it has to be called on client.connection.builder.

This still seems less obvious than it should be. Should a better programmatic solution exist, or should this use case be documented in the readme?

I'm thinking we could modify EntryPoint to take a block in the constructor, and call that when initialising faraday. Something like:

class EntryPoint < Link
  def initialize(url, &block)
    @link = {'href' => url}
    @entry_point = self
    @faraday_block = block
  end

  def default_faraday_block
    lambda do |faraday|
      faraday.request  :json
      faraday.response :json, content_type: /\bjson$/
      @faraday_block.call(faraday) if @faraday_block
      faraday.adapter :net_http
    end
  end
end

Which would let you use faraday.use before the adapter has been set. e.g.

Hyperclient.new('url') do |faraday|
  faraday.use :http_cache
end

Alternatively, the constructor block could just replace default_faraday_block entirely when present.

Thoughts?

[oriolgual]

I agree that there should be a better way to do this. Initializing Hyperclient with a faraday block seems like the best option, or maybe we could do it as an accessor:

client = Hyperclient.new('https://api.github.com')
client.faraday_block = lambda do |faraday|
  faraday.use :http_cache
end

In any case, if you provide a block I would ignore the default block, it feels more natural.

[jagregory]

The only downside I can think of with ignoring the block, is anyone who provides their own block will have to also specify the defaults that Hyperclient expects (as in, the request and response :json options). Is that acceptable?

Either way, I'll put together a pull request with these changes in.

[oriolgual]

What if we keep the default block, but provide a way to add middlewares and adapter? Like:

client = Hyperclient.new('https://api.github.com')
client.faraday_middlewares << :http_cache
clent.adapter = MyCustomAdapter

And then the deafult_faraday_block uses this values to initialize Faraday.

[dblock]

Maybe just letting one assign a connection?

client = Hyperclient.new
client.connection = Faraday.new 'https://api.github.com', headers: ... do |f|
   f.use ....
end

Looking forward to a PR.

[dblock]

Custom Faraday blocks are now fully supported via #75.

Hyperclient.new('https://api.github.com') do |client|
  client.connection(default: false) do |conn|
     conn.request  :json
     conn.response :json, content_type: /\bjson$/
     conn.use :http_cache
     conn.adapter :net_http    
     # etc.
  end
end