providers/docker: only sync folders if they're not already there

lib/vagrant/action/builtin/mixin_synced_folders.rb

@@ -87,9 +87,10 @@ module Vagrant
         # implementation class for the synced folders.
         #
         # @return [Hash<Symbol, Hash<String, Hash>>]
-        def synced_folders(machine, config=nil, **opts)
+        def synced_folders(machine, **opts)
           return cached_synced_folders(machine) if opts[:cached]
 
+          config = opts[:config]
           config ||= machine.config.vm
           folders = {}
 

lib/vagrant/action/builtin/synced_folders.rb

@@ -20,10 +20,11 @@ module Vagrant
         def call(env)
           opts = {
             cached: !!env[:synced_folders_cached],
+            config: env[:synced_folders_config],
           }
 
-          folders = synced_folders(
+          folders = synced_folders(env[:machine], **opts)
-            env[:machine], env[:synced_folders_config], **opts)
+          original_folders = folders
 
           folders.each do |impl_name, fs|
             @logger.info("Synced Folder Implementation: #{impl_name}")
@@ -89,7 +90,7 @@ module Vagrant
           end
 
           # Save the synced folders
-          save_synced_folders(env[:machine], folders, merge: true)
+          save_synced_folders(env[:machine], original_folders, merge: true)
         end
       end
     end

plugins/providers/docker/action/host_machine_sync_folders.rb

@@ -47,6 +47,19 @@ module VagrantPlugins
           proxy_ui.opts[:prefix_spaces] = true
           proxy_ui.opts[:target] = env[:machine].name.to_s
 
+          # Read the existing folders that are setup
+          existing_folders = synced_folders(host_machine, cached: true)
+          existing_ids = {}
+          if existing_folders
+            existing_folders.each do |impl, fs|
+              fs.each do |_name, data|
+                if data[:docker_sfid]
+                  existing_ids[data[:docker_sfid]] = data
+                end
+              end
+            end
+          end
+
           # Sync some folders so that our volumes work later.
           new_config  = VagrantPlugins::Kernel_V2::VMConfig.new
           our_folders = synced_folders(env[:machine])
@@ -59,24 +72,45 @@ module VagrantPlugins
                 data.delete(:type)
               end
 
+              # Generate an ID that is deterministic based on our machine
+              # and Vagrantfile path...
+              id = Digest::MD5.hexdigest(
+                "#{env[:machine].env.root_path}#{env[:machine].name}")
+
               # Generate a new guestpath
               data[:docker_guestpath] = data[:guestpath]
+              data[:docker_sfid] = id
               data[:guestpath] = "/mnt/docker_#{Time.now.to_i}_#{rand(100000)}"
-              data[:id] =
+              data[:id] = id[0...6] + rand(10000).to_s
-                Digest::MD5.hexdigest(Time.now.to_i.to_s)[0...6] +
-                rand(10000).to_s
 
-              # Add this synced folder onto the new config
+              # Add this synced folder onto the new config if we haven't
+              # already shared it before.
+              if !existing_ids.has_key?(id)
                 new_config.synced_folder(
                   data[:hostpath],
                   data[:guestpath],
                   data)
+              else
+                # We already have the folder, so just load its data
+                data = existing_ids[id]
+              end
 
               # Remove from our machine
               env[:machine].config.vm.synced_folders.delete(id)
+
+              # Add the "fixed" folder to our machine
+              data = data.merge({
+                hostpath_exact: true,
+                type: :docker,
+              })
+              env[:machine].config.vm.synced_folder(
+                data[:guestpath],
+                data[:docker_guestpath],
+                data)
             end
           end
 
+          if !new_config.synced_folders.empty?
             # Sync the folders!
             env[:machine].ui.output(I18n.t(
               "docker_provider.host_machine_syncing_folders"))
@@ -90,21 +124,6 @@ module VagrantPlugins
                 host_machine.action_raw(:sync_folders, callable, action_env)
               end
             end
-
-          # Re-add to our machine the "fixed" synced folders
-          new_folders = synced_folders(host_machine, new_config)
-          new_folders.each do |_type, folders|
-            folders.each do |id, data|
-              data = data.merge({
-                hostpath_exact: true,
-                type: :docker,
-              })
-
-              env[:machine].config.vm.synced_folder(
-                data[:guestpath],
-                data[:docker_guestpath],
-                data)
-            end
           end
         end
       end

test/unit/vagrant/action/builtin/mixin_synced_folders_test.rb

@@ -101,7 +101,7 @@ describe Vagrant::Action::Builtin::MixinSyncedFolders do
       other = double("config")
       other.stub(synced_folders: other_folders)
 
-      result = subject.synced_folders(machine, other)
+      result = subject.synced_folders(machine, config: other)
       expect(result.length).to eq(1)
       expect(result[:default]).to eq({
         "bar" => other_folders["bar"],
@@ -137,7 +137,7 @@ describe Vagrant::Action::Builtin::MixinSyncedFolders do
     end
 
     it "returns nil if cached read with no cache" do
-      result = subject.synced_folders(machine, nil, cached: true)
+      result = subject.synced_folders(machine, cached: true)
       expect(result).to be_nil
     end
 
@@ -154,7 +154,7 @@ describe Vagrant::Action::Builtin::MixinSyncedFolders do
       old_folders = folders.dup
       folders.clear
 
-      result = subject.synced_folders(machine, nil, cached: true)
+      result = subject.synced_folders(machine, cached: true)
       expect(result.length).to eq(2)
       expect(result[:default]).to eq({
         "another" => old_folders["another"],
@@ -180,7 +180,7 @@ describe Vagrant::Action::Builtin::MixinSyncedFolders do
       folders.clear
 
       # Read them all back
-      result = subject.synced_folders(machine, nil, cached: true)
+      result = subject.synced_folders(machine, cached: true)
       expect(result.length).to eq(2)
       expect(result[:default]).to eq({
         "foo" => { type: "default" },