Introducing Windows Azure- P26 pptx

CHAPTER 3 ■ WORKING WITH CLOUD QUEUE AND BLOB STORAGE 98 Figure 3-11 is the diagram for the class layout. As noted above, in order to make our components reusable, we define a base class called AzureStorageFacade, which encapsulates the account initialization function in the constructor. We subclass three classes also using the facade design pattern to wrap up all the interfaces used to access Azure basic storages, table, queue and blob, respectively. These three subclasses are AzureStorage, TableStorage, and BlobStorage. In this exercise we are going to use this base class to re-engineer the blob access classes from previous exercise and leave you to apply the first two classes to all existing exercises from previous chapters or use them in future development. Figure 3-11. Class diagram for large data I/O to cloud blob storage tools Listing 3-15 is the implementation of the base class AzureStorageFacade. There is only one member method Initialization() defined, which is used to retrieve the account information from the configuration file. Listing 3-15. Implementation of the Base Class AzureStorageFacade using System; using System.Configuration; namespace AzureForDotNetDevelopers.LargeDataToBlob { using Microsoft.ServiceHosting.ServiceRuntime; using Microsoft.Samples.ServiceHosting.StorageClient; CHAPTER 3 ■ WORKING WITH CLOUD QUEUE AND BLOB STORAGE 99 public class AzureStorageFacade { protected StorageAccountInfo accountInformation; protected int retry = 1; protected int retryInterval = 1000; public StorageAccountInfo StorageAccountInfo { get{ return accountInformation; } } public AzureStorageFacade() { InitializationStorages(); } protected void InitializationStorages() { retry = Convert.ToInt32(ConfigurationManager.AppSettings["Retry"]); retryInterval = Convert.ToInt32(ConfigurationManager.AppSettings["RetryInterval"]); accountInformation = StorageAccountInfo.GetDefaultBlobStorageAccountFromConfiguration(); } } } Listing 3-16 shows the implementation of the blob facade class, which encapsulates all blob storage access functions and attributes of blob storage needed for a client application in a more comprehensive manner than in the implementation in the previous exercise. Listing 3-16. Implementation of the BlobStorageFacade Class Derived from the AzureStorageFacade Class using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Configuration; using System.Collections.Specialized; using System.Threading; using System.IO; namespace AzureForDotNetDevelopers.LargeDataToBlob.CloudStorage.BlobStorage { using Microsoft.ServiceHosting.ServiceRuntime; using Microsoft.Samples.ServiceHosting.StorageClient; using CSharpBuildingBlocks; CHAPTER 3 ■ WORKING WITH CLOUD QUEUE AND BLOB STORAGE 100 public class BlobStorageFacade : AzureStorageFacade { static public long LARGE BLOB SIZE = 2 * 1024 * 1024;// 2 MB protected BlobStorage blobStorage; protected BlobContainer blobContainer; protected string blobContainerName = ConfigurationManager.AppSettings["BlobContainerName"]; protected NameValueCollection metadata = null; protected Thread createBlobWorkerthread = null; public BlobContents Contents { get; set; } public BlobProperties Properties { get; set; } public bool Overwrite { get; set; } public BlobStorageFacade() { blobStorage = BlobStorage.Create( accountInformation); blobStorage.RetryPolicy = RetryPolicies.RetryN(retry, TimeSpan.FromMilliseconds(retryInterval)); blobContainer = blobStorage.GetBlobContainer( blobContainerName); } public BlobStorageFacade(NameValueCollection metadata):this() { metadata = metadata; blobContainer.CreateContainer( metadata, ContainerAccessControl.Private); } public BlobStorageFacade(BlobContents blobContents, BlobProperties blobProperties, bool overwrite) : this(blobProperties.Metadata) { Contents = blobContents; Properties = blobProperties; Overwrite = overwrite; } public BlobContainer BlobContainer { get { return blobContainer; } } public IEnumerable<BlobContainer> GetBlobContainers() { return blobStorage.ListBlobContainers(); } public void CreateBlob() { blobContainer.CreateBlob(Properties, Contents, CHAPTER 3 ■ WORKING WITH CLOUD QUEUE AND BLOB STORAGE 101 Overwrite); } public void DeleteBlob() { if ( blobContainer.DoesBlobExist(Properties.Name)) { blobContainer.DeleteBlob(Properties.Name); } } } } As mentioned before, we use a background worker thread and ICommand design pattern in this application. The base class implementation for these two classes comes from my existing building block collection library. The reference assemblies are called CSharpBuildingBlocks and CSharpBuildingBlocks.QueuedBackgroundWorker. These two assemblies come with the source code download and will be used several places in other chapters. Listing 3-17 and Listing 3-18 are the implementation for CreateBlobStatus and DeleteBlobStatus. A worker thread is created at the time a message arrives for either creating or deleting a blob request. Two member functions are used to handle create or delete activities accordingly. The algorithms for progress are different in these two classes. For blob creation, the percentage of the creation progress is determined by comparing the size of the blob to be created against the actual size of the data that has been committed to cloud blob storage. No incremented progress can be reported to the client application, because the detailed information of a newly created or deleted blob will not be updated until the transactions have been committed on the server. Listing 3-17. The CreateBlobStatus Class Derived from the BlobStorageAction Class using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Configuration; using System.Collections.Specialized; using System.Threading; namespace AzureForDotNetDevelopers.LargeDataToBlob.CloudStorage.BlobStorage { using Microsoft.ServiceHosting.ServiceRuntime; using Microsoft.Samples.ServiceHosting.StorageClient; using CSharpBuildingBlocks; public class CreateBlobStatus : BlobStorageActionStatus, ICommand { public long CreateContentSize { get; set; } public CreateBlobStatus(BlobContents blobContents, BlobProperties blobProperties, CHAPTER 3 ■ WORKING WITH CLOUD QUEUE AND BLOB STORAGE 102 bool overwrite) : base(blobContents, blobProperties, overwrite) { } public void Execute() { try { if ( blobStorageFacade.BlobContainer .DoesBlobExist( blobStorageFacade.Properties.Name)) { var blob = (from m in blobStorageFacade.BlobContainer.ListBlobs(string.Empty, false) where (m as BlobProperties).Name == blobStorageFacade.Properties.Name select m as BlobProperties).Single<BlobProperties>(); percentComplete = (float)(((blob as BlobProperties).ContentLength * 100.0) / (CreateContentSize * 1.0)); System.Diagnostics.Trace.WriteLine( string.Format( " {0}:Execute, percentComplete = <{1}>", this.ToString(), percentComplete ) ); } } catch (Exception ex) { System.Diagnostics.Trace.WriteLine( string.Format( " {0}:Execute,exception caught <{1}>", this.ToString(), ex.Message ) ); } } override protected void blobStorageWorkerThread(object paramters) { try {