Cache resource

README.md

@@ -600,6 +600,19 @@ require 'docker'
 Docker::Container.all({}, Docker::Connection.new('tcp://example.com:2375', {}))
 ```
 
+## Keep connection to Docker alive
+
+Each call will be done through a new established HTTP connection. This can be a bit slow if doing a lot of calls. You can keep the HTTP connection alive like this:
+
+```ruby
+connection = Docker::Connection.new("tcp://example.com:1000", cache_resource: true)
+```
+
+And then use the connection on eahc call like this:
+```ruby
+container = Docker::Image.get(id, {}, connection)
+```
+
 ## Rake Task
 
 To create images through `rake`, a DSL task is provided. For example:

lib/docker/connection.rb

@@ -1,3 +1,5 @@
+require 'json'
+
 # This class represents a Connection to a Docker server. The Connection is
 # immutable in that once the url and options is set they cannot be changed.
 class Docker::Connection
@@ -29,13 +31,24 @@ def initialize(url, opts)
     end
   end
 
-  # The actual client that sends HTTP methods to the Docker server. This value
-  # is not cached, since doing so may cause socket errors after bad requests.
+  # The actual client that sends HTTP methods to the Docker server.
   def resource
-    Excon.new(url, options)
+    if @options[:cache_resource]
+      @resource ||= new_excon
+    else
+      new_excon
+    end
   end
   private :resource
 
+  def new_excon
+    Excon.new(url, options)
+  end
+
+  def reset_resource
+    @resource = nil
+  end
+
   # Send a request to the server with the `
   def request(*args, &block)
     retries ||= 0
@@ -44,6 +57,8 @@ def request(*args, &block)
     begin
       resource.request(request).body
     rescue Excon::Errors::BadRequest => ex
+      reset_resource
+
       if retries < 2
         response_cause = ''
         begin

spec/docker/connection_spec.rb

@@ -64,7 +64,23 @@
   end
 
   describe '#resource' do
+    subject { described_class.new('http://localhost:4243', cache_resource: true) }
+
     its(:resource) { should be_a Excon::Connection }
+
+    it 'reuses the same connection' do
+      previous_resource = subject.__send__(:resource)
+      expect(subject.__send__(:resource).__id__).to eq previous_resource.__id__
+    end
+
+    it 'spawns a new Excon::Connection if encountering a bad request' do
+      previous_resource = subject.__send__(:resource)
+      response = Excon::Response.new
+      error = Excon::Errors::BadRequest.new('Hello world', nil, response)
+      expect(previous_resource).to receive(:request).and_raise(error)
+      expect { subject.request(:get, '/test', {all: true}, {}) }.to raise_error(Docker::Error::ClientError)
+      expect(subject.__send__(:resource).__id__).not_to eq previous_resource.__id__
+    end
   end
 
   describe '#request' do