diff --git a/ChangeLog.md b/ChangeLog.md
index 86537b81..91b93b83 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,3 +1,9 @@
+2016.12 - version 0.11.5-preview
+
+ALL
+* Added the support for setting customer user agent. [#71](https://github.com/Azure/azure-storage-ruby/issues/71)
+* Added the support for hooking in sending requests.
+
 2016.11 - version 0.11.4-preview
 
 ALL
diff --git a/README.md b/README.md
index f932ff29..86c6e560 100644
--- a/README.md
+++ b/README.md
@@ -239,6 +239,19 @@ queues.delete_queue("test-queue")
 
 ```
 
+<a name="Customize the user-agent"></a>
+## Customize the user-agent
+
+You can customize the user-agent string by setting your user agent prefix when creating the service client.
+
+```ruby
+# Require the azure storage rubygem
+require "azure/storage"
+
+# Setup a specific instance of an Azure::Storage::Client with :user_agent_prefix option
+client = Azure::Storage::Client.create(:storage_account_name => "your account name", :storage_access_key => "your access key", :user_agent_prefix => "your application name")
+```
+
 # Getting Started for Contributors
 
 If you would like to become an active contributor to this project please follow the instructions provided in [Azure Projects Contribution Guidelines](http://azure.github.io/guidelines/).
diff --git a/azure-storage.gemspec b/azure-storage.gemspec
index 0620e6cc..65ce9b88 100644
--- a/azure-storage.gemspec
+++ b/azure-storage.gemspec
@@ -41,7 +41,7 @@ Gem::Specification.new do |s|
   s.add_runtime_dependency('azure-core',              '~> 0.1')
   s.add_runtime_dependency('faraday',                 '~> 0.9')
   s.add_runtime_dependency('faraday_middleware',      '~> 0.10')
-  s.add_runtime_dependency('nokogiri',                '~> 1.6')
+  s.add_runtime_dependency('nokogiri',                '~> 1.6.0')
   
   s.add_development_dependency('dotenv',              '~> 2.0')
   s.add_development_dependency('minitest',            '~> 5')
diff --git a/lib/azure/storage/blob/blob_service.rb b/lib/azure/storage/blob/blob_service.rb
index e13df13f..51c3b455 100755
--- a/lib/azure/storage/blob/blob_service.rb
+++ b/lib/azure/storage/blob/blob_service.rb
@@ -38,10 +38,10 @@ class BlobService < StorageService
       include Azure::Storage::Blob
       include Azure::Storage::Blob::Container
       
-      def initialize(options = {})
+      def initialize(options = {}, &block)
         client_config = options[:client] || Azure::Storage
         signer = options[:signer] || Azure::Storage::Core::Auth::SharedKey.new(client_config.storage_account_name, client_config.storage_access_key)
-        super(signer, client_config.storage_account_name, options)
+        super(signer, client_config.storage_account_name, options, &block)
         @host = client.storage_blob_host
       end
 
diff --git a/lib/azure/storage/client.rb b/lib/azure/storage/client.rb
index 1ca78868..556e1d16 100644
--- a/lib/azure/storage/client.rb
+++ b/lib/azure/storage/client.rb
@@ -27,6 +27,7 @@
 
 require 'azure/storage/client_options'
 
+require 'azure/storage/service/storage_service'
 require 'azure/storage/blob/blob_service'
 require 'azure/storage/table/table_service'
 require 'azure/storage/queue/queue_service'
@@ -59,6 +60,7 @@ class Client
     # * +:default_endpoints_protocol+     - String. http or https
     # * +:use_path_style_uri+             - String. Whether use path style URI for specified endpoints
     # * +:ca_file+                        - String. File path of the CA file if having issue with SSL
+    # * +:user_agent_prefix+              - String. The user agent prefix that can identify the application calls the library
     #
     # The valid set of options inlcude:
     # * Storage Emulator: +:use_development_storage+ required, +:development_storage_proxy_uri+ optionally
@@ -76,19 +78,24 @@ class Client
     # When empty options are given, it will try to read settings from Environment Variables. Refer to [Azure::Storage::ClientOptions.env_vars_mapping] for the mapping relationship
     #
     # @return [Azure::Storage::Client]
-    def initialize(options = {})
+    def initialize(options = {}, &block)
       if options.is_a?(Hash)
         options = setup_options if options.length == 0
         options = parse_connection_string(options[:storage_connection_string]) if options[:storage_connection_string]
-      end
 
+        if options.has_key?(:user_agent_prefix)
+          Azure::Storage::Service::StorageService.user_agent_prefix = options[:user_agent_prefix]
+          options.delete :user_agent_prefix
+        end
+      end
+      Azure::Storage::Service::StorageService.register_request_callback &block if block_given?
       reset!(options)
     end
 
     # Azure Blob service client configured from this Azure Storage client instance
     # @return [Azure::Storage::Blob::BlobService]
-    def blob_client(options = {})
-      @blob_client ||= Azure::Storage::Blob::BlobService.new(default_client(options))
+    def blob_client(options = {}, &block)
+      @blob_client ||= Azure::Storage::Blob::BlobService.new(default_client(options), &block)
     end
 
     # Azure Queue service client configured from this Azure Storage client instance
@@ -104,7 +111,6 @@ def table_client(options = {})
     end
 
     class << self
-
       # Public: Creates an instance of [Azure::Storage::Client]
       #
       # ==== Attributes
@@ -127,6 +133,7 @@ class << self
       # * +:default_endpoints_protocol+     - String. http or https
       # * +:use_path_style_uri+             - String. Whether use path style URI for specified endpoints
       # * +:ca_file+                        - String. File path of the CA file if having issue with SSL
+      # * +:user_agent_prefix+              - String. The user agent prefix that can identify the application calls the library
       #
       # The valid set of options inlcude:
       # * Storage Emulator: +:use_development_storage+ required, +:development_storage_proxy_uri+ optionally
@@ -144,8 +151,8 @@ class << self
       # When empty options are given, it will try to read settings from Environment Variables. Refer to [Azure::Storage::ClientOptions.env_vars_mapping] for the mapping relationship
       #
       # @return [Azure::Storage::Client]
-      def create(options={})
-        Client.new(options)
+      def create(options={}, &block)
+        Client.new(options, &block)
       end
 
       # Public: Creates an instance of [Azure::Storage::Client] with Storage Emulator
@@ -155,17 +162,16 @@ def create(options={})
       # * +proxy_uri+    - String. Used with +:use_development_storage+ if emulator is hosted other than localhost.
       #
       # @return [Azure::Storage::Client]
-      def create_development(proxy_uri=nil)
+      def create_development(proxy_uri=nil, &block)
         proxy_uri ||= StorageServiceClientConstants::DEV_STORE_URI
-        create(:use_development_storage => true, :development_storage_proxy_uri => proxy_uri)
+        create(:use_development_storage => true, :development_storage_proxy_uri => proxy_uri, &block)
       end
 
-
       # Public: Creates an instance of [Azure::Storage::Client] from Environment Variables
       #
       # @return [Azure::Storage::Client]
-      def create_from_env
-        create
+      def create_from_env(&block)
+        create &block
       end
 
       # Public: Creates an instance of [Azure::Storage::Client] from Environment Variables
@@ -175,8 +181,8 @@ def create_from_env
       # * +connection_string+    - String. Please refer to https://azure.microsoft.com/en-us/documentation/articles/storage-configure-connection-string/.
       #
       # @return [Azure::Storage::Client]
-      def create_from_connection_string(connection_string)
-        Client.new(connection_string)
+      def create_from_connection_string(connection_string, &block)
+        Client.new(connection_string, &block)
       end
     end
 
diff --git a/lib/azure/storage/queue/queue_service.rb b/lib/azure/storage/queue/queue_service.rb
index 311fb8d6..ef412216 100644
--- a/lib/azure/storage/queue/queue_service.rb
+++ b/lib/azure/storage/queue/queue_service.rb
@@ -30,10 +30,10 @@ module Queue
     include Azure::Storage::Service
     class QueueService < StorageService
 
-      def initialize(options = {})
+      def initialize(options = {}, &block)
         client_config = options[:client] || Azure::Storage
         signer = options[:signer] || Azure::Storage::Core::Auth::SharedKey.new(client_config.storage_account_name, client_config.storage_access_key)
-        super(signer, client_config.storage_account_name, options)
+        super(signer, client_config.storage_account_name, options, &block)
         @host = @client.storage_queue_host
       end
 
diff --git a/lib/azure/storage/service/storage_service.rb b/lib/azure/storage/service/storage_service.rb
index f0bcad45..833be4ac 100755
--- a/lib/azure/storage/service/storage_service.rb
+++ b/lib/azure/storage/service/storage_service.rb
@@ -33,10 +33,11 @@ class StorageService < Azure::Core::SignedService
       # Create a new instance of the StorageService
       #
       # @param signer         [Azure::Core::Auth::Signer] An implementation of Signer used for signing requests.
-      # (optional, Default=Azure::Storage::Auth::SharedKey.new)
+      #                                                   (optional, Default=Azure::Storage::Auth::SharedKey.new)
       # @param account_name   [String] The account name (optional, Default=Azure::Storage.storage_account_name)
       # @param options        [Azure::Storage::Configurable] the client configuration context
-      def initialize(signer=nil, account_name=nil, options = {})
+      def initialize(signer=nil, account_name=nil, options = {}, &block)
+        StorageService.register_request_callback &block if block_given?
         options[:client] = Azure::Storage if options[:client] == nil
         client_config = options[:client]
         signer = signer || Azure::Storage::Core::Auth::SharedKey.new(
@@ -118,6 +119,20 @@ def generate_uri(path='', query={})
       end
         
       class << self
+        # @!attribute user_agent_prefix
+        # @return [Proc] Get or set the user agent prefix
+        attr_accessor :user_agent_prefix
+        
+        # @!attribute request_callback
+        # @return [Proc] The callback before the request is signed and sent
+        attr_reader :request_callback
+
+        # Registers the callback when sending the request
+        # The headers in the request can be viewed or changed in the code block
+        def register_request_callback
+          @request_callback = Proc.new
+        end
+
         # Adds metadata properties to header hash with required prefix
         #
         # metadata  - A Hash of metadata name/value pairs
@@ -157,9 +172,10 @@ def with_value(object, key, value)
         def common_headers(options = {})
           headers = {
             'x-ms-version' => Azure::Storage::Default::STG_VERSION,
-            'User-Agent' => Azure::Storage::Default::USER_AGENT
+            'User-Agent' => user_agent_prefix ? "#{user_agent_prefix}; #{Azure::Storage::Default::USER_AGENT}" : Azure::Storage::Default::USER_AGENT
           }
           headers.merge!({'x-ms-client-request-id' => options[:request_id]}) if options[:request_id]
+          @request_callback.call(headers) if @request_callback
           headers
         end
       end
diff --git a/lib/azure/storage/table/table_service.rb b/lib/azure/storage/table/table_service.rb
index dc905cb5..4a4ad5fa 100755
--- a/lib/azure/storage/table/table_service.rb
+++ b/lib/azure/storage/table/table_service.rb
@@ -31,10 +31,10 @@ module Azure::Storage
   module Table
     class TableService < Service::StorageService
 
-      def initialize(options = {})
+      def initialize(options = {}, &block)
         client_config = options[:client] || Azure::Storage
         signer = options[:signer] || Auth::SharedKey.new(client_config.storage_account_name, client_config.storage_access_key)
-        super(signer, client_config.storage_account_name, options)
+        super(signer, client_config.storage_account_name, options, &block)
         @host = client.storage_table_host
       end
 
diff --git a/lib/azure/storage/version.rb b/lib/azure/storage/version.rb
index 1293f6f2..46fd6ccb 100644
--- a/lib/azure/storage/version.rb
+++ b/lib/azure/storage/version.rb
@@ -28,7 +28,7 @@ class Version
       # Fields represent the parts defined in http://semver.org/
       MAJOR = 0 unless defined? MAJOR
       MINOR = 11 unless defined? MINOR
-      UPDATE = 4 unless defined? UPDATE
+      UPDATE = 5 unless defined? UPDATE
       PRE = 'preview' unless defined? PRE
 
       class << self
diff --git a/test/integration/blob/container/container_metadata_test.rb b/test/integration/blob/container/container_metadata_test.rb
index a00ebdcf..80e9094c 100644
--- a/test/integration/blob/container/container_metadata_test.rb
+++ b/test/integration/blob/container/container_metadata_test.rb
@@ -25,7 +25,12 @@
 require "azure/storage/blob/blob_service"
 
 describe Azure::Storage::Blob::BlobService do
-  subject { Azure::Storage::Blob::BlobService.new }
+  let(:user_agent_prefix) { 'azure_storage_ruby_integration_test' }
+  subject { 
+    Azure::Storage::Blob::BlobService.new { |headers|
+      headers['User-Agent'] = "#{user_agent_prefix}; #{headers['User-Agent']}"
+    }
+  }
   after { ContainerNameHelper.clean }
   
   describe '#set/get_container_metadata' do
diff --git a/test/integration/queue/create_queue_test.rb b/test/integration/queue/create_queue_test.rb
index e5f0db12..d7c60859 100644
--- a/test/integration/queue/create_queue_test.rb
+++ b/test/integration/queue/create_queue_test.rb
@@ -26,7 +26,12 @@
 require "azure/core/http/http_error"
 
 describe Azure::Storage::Queue::QueueService do
-  subject { Azure::Storage::Queue::QueueService.new }
+  let(:user_agent_prefix) { 'azure_storage_ruby_integration_test' }
+  subject { 
+    Azure::Storage::Queue::QueueService.new { |headers|
+      headers['User-Agent'] = "#{user_agent_prefix}; #{headers['User-Agent']}"
+    }
+  }
   
   describe '#create_queue' do
     let(:queue_name){ QueueNameHelper.name }
diff --git a/test/integration/table/create_table_test.rb b/test/integration/table/create_table_test.rb
index 04e85461..b451356d 100644
--- a/test/integration/table/create_table_test.rb
+++ b/test/integration/table/create_table_test.rb
@@ -27,7 +27,12 @@
 
 describe Azure::Storage::Table::TableService do
   describe "#create_table" do
-    subject { Azure::Storage::Table::TableService.new }
+    let(:user_agent_prefix) { 'azure_storage_ruby_integration_test' }
+    subject { 
+      Azure::Storage::Table::TableService.new { |headers|
+        headers['User-Agent'] = "#{user_agent_prefix}; #{headers['User-Agent']}"
+      }
+    }
     let(:table_name){ TableNameHelper.name }
     after { TableNameHelper.clean }
 
diff --git a/test/unit/blob/blob_service_test.rb b/test/unit/blob/blob_service_test.rb
index b9532514..babf9a1c 100644
--- a/test/unit/blob/blob_service_test.rb
+++ b/test/unit/blob/blob_service_test.rb
@@ -30,14 +30,18 @@
 require 'azure/storage/service/signed_identifier'
 
 describe Azure::Storage::Blob::BlobService do
-
-  subject { Azure::Storage::Blob::BlobService.new }
+  let(:user_agent_prefix) { 'azure_storage_ruby_unit_test' }
+  subject { 
+    Azure::Storage::Blob::BlobService.new { |headers|
+      headers['User-Agent'] = "#{user_agent_prefix}; #{headers['User-Agent']}"
+    }
+  }
   let(:serialization) { Azure::Storage::Blob::Serialization }
   let(:uri) { URI.parse 'http://foo.com' }
   let(:query) { {} }
   let(:x_ms_version) { Azure::Storage::Default::STG_VERSION }
   let(:user_agent) { Azure::Storage::Default::USER_AGENT }
-  let(:request_headers) { {'x-ms-version' => x_ms_version, 'User-Agent' => user_agent} }
+  let(:request_headers) { {'x-ms-version' => x_ms_version, 'User-Agent' => "#{user_agent_prefix}; #{user_agent}"} }
   let(:request_body) { 'request-body' }
 
   let(:response_headers) { {} }
@@ -186,7 +190,7 @@
             'x-ms-meta-MetadataKey' => 'MetaDataValue',
             'x-ms-meta-MetadataKey1' => 'MetaDataValue1',
             'x-ms-version' => x_ms_version,
-            'User-Agent' => user_agent
+            'User-Agent' => "#{user_agent_prefix}; #{user_agent}"
           }
           subject.stubs(:container_uri).with(container_name, {}).returns(uri)
           serialization.stubs(:container_from_headers).with(response_headers).returns(container)
@@ -204,7 +208,7 @@
         let(:options) { {:public_access_level => public_access_level} }
 
         before do
-          request_headers = {'x-ms-blob-public-access' => public_access_level, 'x-ms-version' => x_ms_version, 'User-Agent' => user_agent}
+          request_headers = {'x-ms-blob-public-access' => public_access_level, 'x-ms-version' => x_ms_version, 'User-Agent' => "#{user_agent_prefix}; #{user_agent}"}
           subject.stubs(:container_uri).with(container_name, {}).returns(uri)
           subject.stubs(:call).with(verb, uri, nil, request_headers, options).returns(response)
           serialization.stubs(:container_from_headers).with(response_headers).returns(container)
@@ -469,7 +473,7 @@
         {'x-ms-meta-MetadataKey' => 'MetaDataValue',
          'x-ms-meta-MetadataKey1' => 'MetaDataValue1',
          'x-ms-version' => x_ms_version,
-         'User-Agent' => user_agent
+         'User-Agent' => "#{user_agent_prefix}; #{user_agent}"
          }
       }
 
@@ -632,7 +636,7 @@
             'x-ms-blob-content-length' => blob_length.to_s,
             'x-ms-sequence-number' => 0.to_s,
             'x-ms-version' => x_ms_version,
-            'User-Agent' => user_agent
+            'User-Agent' => "#{user_agent_prefix}; #{user_agent}"
           }
         }
 
@@ -744,7 +748,7 @@
             'x-ms-range' => "bytes=#{start_range}-#{end_range}",
             'Content-Type' => '',
             'x-ms-version' => x_ms_version,
-            'User-Agent' => user_agent
+            'User-Agent' => "#{user_agent_prefix}; #{user_agent}"
           }
         }
 
@@ -841,7 +845,7 @@
             'x-ms-page-write' => 'clear',
             'Content-Type' => '',
             'x-ms-version' => x_ms_version,
-            'User-Agent' => user_agent
+            'User-Agent' => "#{user_agent_prefix}; #{user_agent}"
           }
         }
 
@@ -905,7 +909,7 @@
         let(:content) { 'some content' }
         let(:block_id) { 'block-id' }
         let(:server_generated_content_md5) { 'server-content-md5' }
-        let(:request_headers) { {'x-ms-version' => x_ms_version, 'User-Agent' => user_agent} }
+        let(:request_headers) { {'x-ms-version' => x_ms_version, 'User-Agent' => "#{user_agent_prefix}; #{user_agent}"} }
 
         before {
           query.update({'comp' => 'block', 'blockid' => Base64.strict_encode64(block_id)})
@@ -952,7 +956,7 @@
           {
             'x-ms-blob-type' => 'BlockBlob',
             'x-ms-version' => x_ms_version,
-            'User-Agent' => user_agent
+            'User-Agent' => "#{user_agent_prefix}; #{user_agent}"
           }
         }
 
@@ -1048,7 +1052,7 @@
         let(:verb) { :put }
         let(:request_body) { 'body' }
         let(:block_list) { mock() }
-        let(:request_headers) { {'x-ms-version' => x_ms_version, 'User-Agent' => user_agent} }
+        let(:request_headers) { {'x-ms-version' => x_ms_version, 'User-Agent' => "#{user_agent_prefix}; #{user_agent}"} }
 
         before {
           query.update({'comp' => 'blocklist'})
@@ -1294,7 +1298,7 @@
         describe 'when both start_range and end_range are provided' do
           let(:start_range) { 255 }
           let(:end_range) { 512 }
-          let(:request_headers) { {'x-ms-version' => x_ms_version, 'User-Agent' => user_agent} }
+          let(:request_headers) { {'x-ms-version' => x_ms_version, 'User-Agent' => "#{user_agent_prefix}; #{user_agent}"} }
 
           it 'modifies the request headers with the desired range' do
             request_headers['x-ms-range'] = "bytes=#{start_range}-#{end_range}"
@@ -1348,7 +1352,7 @@
         let(:verb) { :put }
         let(:query) { {'comp' => 'properties'} }
         let(:size) { 2048 }
-        let(:request_headers) { {'x-ms-version' => x_ms_version, 'User-Agent' => user_agent, 'x-ms-blob-content-length' => size.to_s} }
+        let(:request_headers) { {'x-ms-version' => x_ms_version, 'User-Agent' => "#{user_agent_prefix}; #{user_agent}", 'x-ms-blob-content-length' => size.to_s} }
 
         before {
           subject.stubs(:blob_uri).with(container_name, blob_name, query).returns(uri)
@@ -1396,7 +1400,7 @@
         let(:query) { {'comp' => 'properties'} }
         let(:action) { :update }
         let(:number) { 1024 }
-        let(:request_headers) { {'x-ms-version' => x_ms_version, 'User-Agent' => user_agent} }
+        let(:request_headers) { {'x-ms-version' => x_ms_version, 'User-Agent' => "#{user_agent_prefix}; #{user_agent}"} }
 
         before {
           subject.stubs(:blob_uri).with(container_name, blob_name, query).returns(uri)
@@ -1479,7 +1483,7 @@
             'x-ms-blob-type' => 'AppendBlob',
             'Content-Length' => 0.to_s,
             'x-ms-version' => x_ms_version,
-            'User-Agent' => user_agent
+            'User-Agent' => "#{user_agent_prefix}; #{user_agent}"
           }
         }
 
@@ -1608,7 +1612,7 @@
         let(:lease_id) { 'lease_id' }
         let(:max_size) { 123 }
         let(:append_position) { 999 }
-        let(:request_headers) { {'x-ms-version' => x_ms_version, 'User-Agent' => user_agent} }
+        let(:request_headers) { {'x-ms-version' => x_ms_version, 'User-Agent' => "#{user_agent_prefix}; #{user_agent}"} }
 
         before {
           query.update({'comp' => 'appendblock'})
@@ -1693,7 +1697,7 @@
 
       describe '#set_blob_properties' do
         let(:verb) { :put }
-        let(:request_headers) { {'x-ms-version' => x_ms_version, 'User-Agent' => user_agent} }
+        let(:request_headers) { {'x-ms-version' => x_ms_version, 'User-Agent' => "#{user_agent_prefix}; #{user_agent}"} }
 
         before {
           query.update({'comp' => 'properties'})
@@ -1793,7 +1797,7 @@
       describe '#set_blob_metadata' do
         let(:verb) { :put }
         let(:blob_metadata) { {'MetadataKey' => 'MetaDataValue', 'MetadataKey1' => 'MetaDataValue1'} }
-        let(:request_headers) { {'x-ms-meta-MetadataKey' => 'MetaDataValue', 'x-ms-meta-MetadataKey1' => 'MetaDataValue1', 'x-ms-version' => x_ms_version, 'User-Agent' => user_agent} }
+        let(:request_headers) { {'x-ms-meta-MetadataKey' => 'MetaDataValue', 'x-ms-meta-MetadataKey1' => 'MetaDataValue1', 'x-ms-version' => x_ms_version, 'User-Agent' => "#{user_agent_prefix}; #{user_agent}"} }
 
         before {
           query.update({'comp' => 'metadata'})
@@ -1820,7 +1824,7 @@
 
       describe '#get_blob_properties' do
         let(:verb) { :head }
-        let(:request_headers) { {'x-ms-version' => x_ms_version, 'User-Agent' => user_agent} }
+        let(:request_headers) { {'x-ms-version' => x_ms_version, 'User-Agent' => "#{user_agent_prefix}; #{user_agent}"} }
 
         before {
           subject.stubs(:blob_uri).with(container_name, blob_name, query).returns(uri)
@@ -1868,7 +1872,7 @@
 
       describe '#get_blob_metadata' do
         let(:verb) { :get }
-        let(:request_headers) { {'x-ms-version' => x_ms_version, 'User-Agent' => user_agent} }
+        let(:request_headers) { {'x-ms-version' => x_ms_version, 'User-Agent' => "#{user_agent_prefix}; #{user_agent}"} }
         
         before {
           query['comp']='metadata'