add min_size policy for the resource pool

Change-Id: I7a2e03c7dd2100d8cd5254997c086f16b44efae0

lib/cloud_controller/config.rb

@@ -95,6 +95,7 @@ class VCAP::CloudController::Config < VCAP::Config
 
       :resource_pool => {
         optional(:maximum_size) => Integer,
+        optional(:minimum_size) => Integer,
         optional(:resource_directory_key) => String,
         :fog_connection => {
           :provider => String,

lib/cloud_controller/resource_pool.rb

@@ -17,6 +17,7 @@ def configure(config = {})
       opts = config[:resource_pool] || {}
       @connection_config = opts[:fog_connection]
       @resource_directory_key = opts[:resource_directory_key] || "cc-resources"
+      @minimum_size = opts[:minimum_size] || 0
       @maximum_size = opts[:maximum_size] || 512 * 1024 * 1024 # MB
     end
 
@@ -84,13 +85,20 @@ def logger
     end
 
     def resource_known?(descriptor)
-      key = key_from_sha1(descriptor["sha1"])
-      resource_dir.files.head(key)
+      size = descriptor["size"]
+      if size_allowed?(size)
+        key = key_from_sha1(descriptor["sha1"])
+        resource_dir.files.head(key)
+      end
     end
 
     def resource_allowed?(path)
       stat = File.stat(path)
-      File.file?(path) && !stat.symlink? && stat.size < maximum_size
+      File.file?(path) && !stat.symlink? && size_allowed?(stat.size)
+    end
+
+    def size_allowed?(size)
+      size && size > minimum_size && size < maximum_size
     end
 
     # Called after we sanity-check the input.

spec/resource_pool_spec.rb

@@ -44,5 +44,30 @@ module VCAP::CloudController
         ResourcePool.add_directory(@tmpdir)
       end
     end
+
+    describe "#size_allowed?" do
+      before do
+        @minimum_size = 5
+        @maximum_size = 7
+        ResourcePool.minimum_size = @minimum_size
+        ResourcePool.maximum_size = @maximum_size
+      end
+
+      it "should return true for a size between min and max size" do
+        ResourcePool.send(:size_allowed?, @minimum_size + 1).should be_true
+      end
+
+      it "should return false for a size < min size" do
+        ResourcePool.send(:size_allowed?, @minimum_size - 1).should be_false
+      end
+
+      it "should return false for a size > max size" do
+        ResourcePool.send(:size_allowed?, @maximum_size + 1).should be_false
+      end
+
+      it "should return false for a nil size" do
+        ResourcePool.send(:size_allowed?, nil).should be_false
+      end
+    end
   end
 end