Introducing Windows Azure- P26 pptx

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 ac

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;

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;

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,

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,

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 {