providers/docker: docker-attach command for following output

plugins/providers/docker/command/attach.rb

@@ -0,0 +1,88 @@
+module VagrantPlugins
+  module DockerProvider
+    module Command
+      class Attach < Vagrant.plugin("2", :command)
+        def self.synopsis
+          "attaches to the output stream of a container"
+        end
+
+        def execute
+          options = {}
+          options[:follow] = false
+          options[:prefix] = true
+
+          opts = OptionParser.new do |o|
+            o.banner = "Usage: vagrant docker-attach [options]"
+            o.separator ""
+            o.separator "Options:"
+            o.separator ""
+
+            o.on("--[no-]follow", "Continue streaming in log output") do |f|
+              options[:follow] = f
+            end
+
+            o.on("--[no-]prefix", "Don't prefix output with machine names") do |p|
+              options[:prefix] = p
+            end
+          end
+
+          # Parse the options
+          argv = parse_options(opts)
+          return if !argv
+
+          output_options = {}
+          output_options[:prefix] = false if !options[:prefix]
+
+          # TODO: exit with exit status != 0 if all machines are unknown
+          # or not created.
+
+          # Go through each machine and execute the client on it
+          with_target_vms(argv) do |machine|
+            if machine.provider_name != :docker
+              machine.ui.output(I18n.t("docker_provider.not_docker_provder"))
+              next
+            end
+
+            state = machine.state
+            if state == :host_state_unknown
+              machine.ui.output(I18n.t("docker_provider.attach_host_state_unknown"))
+              next
+            elsif state == :not_created
+              machine.ui.output(I18n.t("docker_provider.not_created_skip"))
+              next
+            end
+
+            command = ["docker", "logs"]
+            command << "--follow" if options[:follow]
+            command << machine.id
+
+            data_acc = ""
+            machine.provider.driver.execute(*command) do |type, data|
+              # Accumulate the data so we only output lines at a time
+              data_acc << data
+
+              # If we have a newline, then output all the lines we have so far
+              if data_acc.include?("\n")
+                lines    = data_acc.split("\n")
+
+                if !data_acc.end_with?("\n")
+                  data_acc = lines.pop.chomp
+                else
+                  data_acc = ""
+                end
+
+                lines.each do |line|
+                  line = " " if line == ""
+                  machine.ui.output(line, **output_options)
+                end
+              end
+            end
+
+            # Output any remaining data
+            machine.ui.output(data_acc, **output_options) if !data_acc.empty?
+          end
+        end
+      end
+    end
+  end
+end

plugins/providers/docker/driver.rb

@@ -99,8 +99,6 @@ module VagrantPlugins
         end
       end
 
-      private
-
       def execute(*cmd, &block)
         @executor.execute(*cmd, &block)
       end

plugins/providers/docker/executor/vagrant.rb

@@ -34,14 +34,23 @@ module VagrantPlugins
             if !fenced
               index = stdout.index(start_fence)
               if index
+                fenced = true
+
                 index += start_fence.length
                 stdout = stdout[index..-1]
                 stdout.chomp!
-              end
-            end
 
+                # We're now fenced, send all the data through
+                if block
+                  block.call(:stdout, stdout)
+                  block.call(:stderr, stderr)
+                end
+              end
+            else
+              # If we're already fenced, just send the data through.
               block.call(type, data) if block && fenced
             end
+          end
 
           if code != 0
             raise Errors::ExecuteError,

plugins/providers/docker/plugin.rb

@@ -22,6 +22,12 @@ module VagrantPlugins
         Provider
       end
 
+      command("docker-attach", primary: false) do
+        require_relative "command/attach"
+        init!
+        Command::Attach
+      end
+
       config(:docker, :provider) do
         require_relative 'config'
         init!

templates/locales/providers_docker.yml

@@ -1,5 +1,9 @@
 en:
   docker_provider:
+    attach_host_state_unknown: |-
+      This container requires a host VM, and the state of that VM
+      is unknown. Run `vagrant up` to verify that the container and
+      its host VM is running, then try again.
     creating: |-
       Creating the container...
     created: |-
@@ -11,6 +15,10 @@ en:
     host_machine_starting: |-
       Vagrant will now create or start a local VM to act as the Docker
       host. You'll see the output of the `vagrant up` for this VM below.
+    not_created_skip: |-
+      Container not created. Skipping.
+    not_docker_provider: |-
+      Not backed by Docker provider. Skipping.
 
     messages:
       destroying: |-