Building Your First Windows Azure Application

Training Kits里的第一篇实例教程，简单记录下过程，并根据理解做些旁注，方便日后查看。

1. 新建一个Cloud Service工程, 增加一个ASP.NET Web Role

2. 增加一个Class Library, 添加所需References，定义Entity Schema -- GuestBookEntry.cs

GuestBookEntry.cs
 using System;
using Microsoft.WindowsAzure.StorageClient;
 
namespace GuestBook_Data
{
    public class GuestBookEntry : TableServiceEntity
    {
        public GuestBookEntry()
        {
            PartitionKey = DateTime.UtcNow.ToString("MMddyyyy");
 
            // Row key allows sorting, so we make sure the rows come back in time order.
            RowKey = string.Format("{0:10}_{1}", DateTime.MaxValue.Ticks - DateTime.Now.Ticks, Guid.NewGuid());
        }
 
        public string Message { get; set; }
        public string GuestName { get; set; }
        public string PhotoUrl { get; set; }
        public string ThumbnailUrl { get; set; }
    }
}
 

注：

定义的 Entity 存于 Windows Azure table 中，故继承自 TableServiceEntity。

TableServiceEntity 类中定义了PartititionKey, RowKey 和 TimeStamp，该3个字段是存在Windows Azure table 中必要的字段，其中 PartitionKey 和 RowKey 都是string类型，合起来可以确定一个 DataServiceKey，进而可以唯一确定 Table 中的一个 Entity。

该例在 Entity 构造函数中对 PartititionKey, RowKey 赋值，以便在新建立一个 Entity 时无须显式的为这两个字段赋值。其中用日期作为PartititionKey的值，这样对于每一天建立的Entities都会有一个Partition, 一般来讲， PartititionKey的选值需要考虑到节点间的负载平衡问题。 RowKey用反序的时间加一个guid来确定，加guid为了保证唯一性，时间反转则是考虑到排序问题，总是让最新的entities排在前面。

3. 定义DataContext -- GuestBookDataContext.cs

GuestBookDataContext.cs
 using System.Linq;
 
using Microsoft.WindowsAzure;
using Microsoft.WindowsAzure.StorageClient;
 
namespace GuestBook_Data
{
    public class GuestBookDataContext : TableServiceContext
    {
        public GuestBookDataContext(string baseAddress, StorageCredentials credentials)
            : base(baseAddress, credentials)
        { 
        }
 
        public IQueryable<GuestBookEntry> GuestBookEntry
        {
            get
            {
                return this.CreateQuery<GuestBookEntry>("GuestBookEntry");
            }
        }
    }
}
 

注：

同样对应于table的DataContext需要继承于 TableServiceContext 类。其中构造函数中StorageCredentials参数存储通过storage account访问Windows Azure storage service需要的验证信息等。

4. 定义GuestBookEntryDataSource.cs

GuestBookEntryDataSource.cs
 using System;
using System.Linq;
using System.Collections.Generic;
 
using Microsoft.WindowsAzure;
using Microsoft.WindowsAzure.StorageClient;
 
namespace GuestBook_Data
{
    public class GuestBookEntryDataSource
    {
        private static CloudStorageAccount storageAccount;
        private GuestBookDataContext context;
        
        public GuestBookEntryDataSource()
        {
            this.context = new GuestBookDataContext(storageAccount.TableEndpoint.AbsoluteUri, storageAccount.Credentials);
            this.context.RetryPolicy = RetryPolicies.Retry(3, TimeSpan.FromSeconds(1));
        }
 
        static GuestBookEntryDataSource()
        {
            storageAccount = CloudStorageAccount.FromConfigurationSetting("DataConnectionString");
 
            CloudTableClient.CreateTablesFromModel(
                typeof(GuestBookDataContext), storageAccount.TableEndpoint.AbsoluteUri, storageAccount.Credentials);
        }
 
        public IEnumerable<GuestBookEntry> Select()
        {
            var results = from g in this.context.GuestBookEntry
                          where g.PartitionKey == DateTime.UtcNow.ToString("MMddyyyy")
                          select g;
            return results;
        }
 
        public void AddGuestBookEntry(GuestBookEntry newItem)
        {
            this.context.AddObject("GuestBookEntry", newItem);
            this.context.SaveChanges();
        }
 
        public void UpdateImageThumbnail(string partitionKey, string rowKey, string thumbUrl)
        {
            var results = from g in this.context.GuestBookEntry
                          where g.PartitionKey == partitionKey && g.RowKey == rowKey
                          select g;
 
            var entry = results.FirstOrDefault<GuestBookEntry>();
            entry.ThumbnailUrl = thumbUrl;
            this.context.UpdateObject(entry);
            this.context.SaveChanges();
        }
    }
}
 

注：

静态构造函数中 storageAccount = CloudStorageAccount.FromConfigurationSetting("DataConnectionString"); 配置信息存储在GuestBook_WebRole中，见下图：

5. 利用 Web Role 来完成UI部分. UI 部分的 code 如下

Default.aspx.cs

using System;

using System.Web.UI;

using System.Net;

using GuestBook_Data;

using Microsoft.WindowsAzure;

using Microsoft.WindowsAzure.StorageClient;

namespace GuestBook_WebRole

{

    public partial class _Default : System.Web.UI.Page

    {

        private static bool storageInitialized = false;

        private static object gate = new Object();

        private static CloudBlobClient blobStorage;

        private static CloudQueueClient queueStorage;

        protected void Page_Load(object sender, EventArgs e)

        {

            if (!Page.IsPostBack)

            {

                Timer1.Enabled = true;

            }

        }

        protected void SignButton_Click(object sender, EventArgs e)

        {

            if (FileUpload1.HasFile)

            {

                InitializeStorage();

                // upload the image to blob storage

                string uniqueBlobName = string.Format("image_{0}.jpg", Guid.NewGuid().ToString());

                CloudBlobContainer container = blobStorage.GetContainerReference("guestbookpics");

                CloudBlockBlob blob = container.GetBlockBlobReference(uniqueBlobName);

                blob.Properties.ContentType = FileUpload1.PostedFile.ContentType;

                blob.UploadFromStream(FileUpload1.FileContent);

                System.Diagnostics.Trace.TraceInformation(

                    "Uploaded image '{0}' to blob storage as '{1}'", FileUpload1.FileName, uniqueBlobName);

                // create a new entry in table storage

                GuestBookEntry entry = new GuestBookEntry() {

                    GuestName = NameTextBox.Text,

                    Message = MessageTextBox.Text,

                    PhotoUrl = blob.Uri.ToString(),

                    ThumbnailUrl = blob.Uri.ToString() };

                GuestBookEntryDataSource ds = new GuestBookEntryDataSource();

                ds.AddGuestBookEntry(entry);

                System.Diagnostics.Trace.TraceInformation(

                    "Added entry {0}-{1} in table storage for guest '{2}'",

                    entry.PartitionKey, entry.RowKey, entry.GuestName);

                // queue a message to process the image

                var queue = queueStorage.GetQueueReference("guestthumbs");

                var message = new CloudQueueMessage(String.Format("{0},{1},{2}", uniqueBlobName, entry.PartitionKey, entry.RowKey));

                queue.AddMessage(message);

                System.Diagnostics.Trace.TraceInformation("Queued message to process blob '{0}'", uniqueBlobName);

            }

            NameTextBox.Text = "";

            MessageTextBox.Text = "";

            DataList1.DataBind();

        }

        protected void Timer1_Tick(object sender, EventArgs e)

        {

            DataList1.DataBind();

        }

        private void InitializeStorage()

        {

            if (storageInitialized)

            {

                return;

            }

            lock (gate)

            {

                if (storageInitialized)

                {

                    return;

                }

                try

                {

                    // read account configuration settings

                    var storageAccount = CloudStorageAccount.FromConfigurationSetting("DataConnectionString");

                    // create blob container for images

                    blobStorage = storageAccount.CreateCloudBlobClient();

                    CloudBlobContainer container = blobStorage.GetContainerReference("guestbookpics");

                    container.CreateIfNotExist();

                    // configure container for public access

                    var permissions = container.GetPermissions();

                    permissions.PublicAccess = BlobContainerPublicAccessType.Container;

                    container.SetPermissions(permissions);

                    // create queue to communicate with worker role

                    queueStorage = storageAccount.CreateCloudQueueClient();

                    CloudQueue queue = queueStorage.GetQueueReference("guestthumbs");

                    queue.CreateIfNotExist();

                }

                catch (WebException)

                {

                    throw new WebException("Storage services initialization failure. "

                        + "Check your storage account configuration settings. If running locally, "

                        + "ensure that the Development Storage service is running.");

                }

                storageInitialized = true;

            }

        }

    }

}

注：

InitializeStorage方法建立了一个blob container用来存储图片，并且设置相应权限。

点击Sign button时，将Image信息存储于blob storage, 将GuestBook Entity信息存储于table storage。

6. 增加一个storage account settings，双击GuestBook_WebRole，Add Settings

7. 修改WebRole.cs的 OnStart() 方法

WebRole.cs

using System.Linq;
using Microsoft.WindowsAzure.Diagnostics;
using Microsoft.WindowsAzure.ServiceRuntime;
using Microsoft.WindowsAzure;
 
namespace GuestBook_WebRole
{
    public class WebRole : RoleEntryPoint
    {
        public override bool OnStart()
        {
            DiagnosticMonitor.Start("DiagnosticsConnectionString");
 
            // For information on handling configuration changes
            // see the MSDN topic at http://go.microsoft.com/fwlink/?LinkId=166357.
            RoleEnvironment.Changing += RoleEnvironmentChanging;
 
            CloudStorageAccount.SetConfigurationSettingPublisher((configName, configSetter) =>
            {
                configSetter(RoleEnvironment.GetConfigurationSettingValue(configName));
            });
 
            return base.OnStart();
        }
 
        private void RoleEnvironmentChanging(object sender, RoleEnvironmentChangingEventArgs e)
        {
            // If a configuration setting is changing
            if (e.Changes.Any(change => change is RoleEnvironmentConfigurationSettingChange))
            {
                // Set e.Cancel to true to restart this role instance
                e.Cancel = true;
            }
        }
    }
}

8. 新建一个Worker Role

WorkerRole.cs

using System;
using System.Diagnostics;
using System.Linq;
using System.Net;
using Microsoft.WindowsAzure.Diagnostics;
using Microsoft.WindowsAzure.ServiceRuntime;
 
using System.Drawing;
using System.IO;
using GuestBook_Data;
using Microsoft.WindowsAzure;
using Microsoft.WindowsAzure.StorageClient;
 
namespace GuestBook_WorkerRole
{
    public class WorkerRole : RoleEntryPoint
    {
        private CloudQueue queue;
        private CloudBlobContainer container;
 
        public override void Run()
        {
            Trace.TraceInformation("Listening for queue messages...");
 
            while (true)
            {
                try
                {
                    // retrieve a new message from the queue
                    CloudQueueMessage msg = queue.GetMessage();
                    if (msg != null)
                    {
                        // parse message retrieved from queue
                        var messageParts = msg.AsString.Split(new char[] { ',' });
                        var uri = messageParts[0];
                        var partitionKey = messageParts[1];
                        var rowkey = messageParts[2];
                        Trace.TraceInformation("Processing image in blob '{0}'.", uri);
 
                        // download original image from blob storage
                        CloudBlockBlob imageBlob = container.GetBlockBlobReference(uri);
                        MemoryStream image = new MemoryStream();
                        imageBlob.DownloadToStream(image);
                        image.Seek(0, SeekOrigin.Begin);
 
                        // create a thumbnail image and upload into a blob
                        string thumbnailUri = String.Concat(Path.GetFileNameWithoutExtension(uri), "_thumb.jpg");
                        CloudBlockBlob thumbnailBlob = container.GetBlockBlobReference(thumbnailUri);
                        thumbnailBlob.UploadFromStream(CreateThumbnail(image));
 
                        // update the entry in table storage to point to the thumbnail
                        var ds = new GuestBookEntryDataSource();
                        ds.UpdateImageThumbnail(partitionKey, rowkey, thumbnailBlob.Uri.AbsoluteUri);
 
                        // remove message from queue
                        queue.DeleteMessage(msg);
 
                        Trace.TraceInformation("Generated thumbnail in blob '{0}'.", thumbnailBlob.Uri);
                    }
                    else
                    {
                        System.Threading.Thread.Sleep(1000);
                    }
                }
                catch (StorageClientException e)
                {
                    Trace.TraceError("Exception when processing queue item. Message: '{0}'", e.Message);
                    System.Threading.Thread.Sleep(5000);
                }
            }
        }
 
        public override bool OnStart()
        {
            // Set the maximum number of concurrent connections 
            ServicePointManager.DefaultConnectionLimit = 12;
 
            DiagnosticMonitor.Start("DiagnosticsConnectionString");
 
            // For information on handling configuration changes
            // see the MSDN topic at http://go.microsoft.com/fwlink/?LinkId=166357.
            RoleEnvironment.Changing += RoleEnvironmentChanging;
            
            // read storage account configuration settings
            CloudStorageAccount.SetConfigurationSettingPublisher((configName, configSetter) =>
            {
                configSetter(RoleEnvironment.GetConfigurationSettingValue(configName));
            });
 
            var storageAccount = CloudStorageAccount.FromConfigurationSetting("DataConnectionString");
 
            // initialize blob storage
            CloudBlobClient blobStorage = storageAccount.CreateCloudBlobClient();
            container = blobStorage.GetContainerReference("guestbookpics");
 
            // initialize queue storage 
            CloudQueueClient queueStorage = storageAccount.CreateCloudQueueClient();
            queue = queueStorage.GetQueueReference("guestthumbs");
 
            Trace.TraceInformation("Creating container and queue...");
 
            bool storageInitialized = false;
            while (!storageInitialized)
            {
                try
                {
                    // create the blob container and allow public access
                    container.CreateIfNotExist();
                    var permissions = container.GetPermissions();
                    permissions.PublicAccess = BlobContainerPublicAccessType.Container;
                    container.SetPermissions(permissions);
 
                    // create the message queue
                    queue.CreateIfNotExist();
                    storageInitialized = true;
                }
                catch (StorageClientException e)
                {
                    if (e.ErrorCode == StorageErrorCode.TransportError)
                    {
                        Trace.TraceError("Storage services initialization failure. "
                          + "Check your storage account configuration settings. If running locally, "
                          + "ensure that the Development Storage service is running. Message: '{0}'", e.Message);
                        System.Threading.Thread.Sleep(5000);
                    }
                    else
                    {
                        throw;
                    }
                }
            }
 
            return base.OnStart();
        }
 
        private void RoleEnvironmentChanging(object sender, RoleEnvironmentChangingEventArgs e)
        {
            // If a configuration setting is changing
            if (e.Changes.Any(change => change is RoleEnvironmentConfigurationSettingChange))
            {
                // Set e.Cancel to true to restart this role instance
                e.Cancel = true;
            }
        }
 
        private Stream CreateThumbnail(Stream input)
        {
            var orig = new Bitmap(input);
            int width;
            int height;
            if (orig.Width > orig.Height)
            {
                width = 128;
                height = 128 * orig.Height / orig.Width;
            }
            else
            {
                height = 128;
                width = 128 * orig.Width / orig.Height;
            }
            var thumb = new Bitmap(width, height);
            using (Graphics graphic = Graphics.FromImage(thumb))
            {
                graphic.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
                graphic.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
                graphic.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality;
                graphic.DrawImage(orig, 0, 0, width, height);
                var ms = new MemoryStream();
                thumb.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
                ms.Seek(0, SeekOrigin.Begin);
                return ms;
            }
        }
    }
}

注：

至此，该程序应该可以运行了，完成的功能就是用户通过页面上传GuestBook信息，其中Image存储于blob storage中，GuestBook Entity存储于table storage中， web role和worker role之间通过queue storage进行消息的传递，用户发的消息以一定格式存储于queue storage中，在worker role中以一定频率去读取queue storage中的信息并进行相应处理。

posted @ 2009-12-24 15:18 咋攒都五块阅读(579) 评论(0) 编辑收藏举报

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