Tutorial: Implement a geo-distributed database (Azure SQL Database)

Applies to: Azure SQL Database

Configure a database in SQL Database and client application for failover to a remote region and test a failover plan. You learn how to:

If you don't have an Azure subscription, create a Trial Subscription before you begin.

Prerequisites

To complete the tutorial, make sure you've installed the following items:

• Azure PowerShell

• A single database in Azure SQL Database. To create one use,

  • The Azure portal
  • The Azure CLI
  • PowerShell

  Note

  The tutorial uses the AdventureWorksLT sample database.

Create a failover group

Using Azure PowerShell, create failover groups between an existing server and a new server in another region. Then add the sample database to the failover group.

$admin = "<adminName>"
$password = "<password>"
$resourceGroup = "<resourceGroupName>"
$location = "<resourceGroupLocation>"
$server = "<serverName>"
$database = "<databaseName>"
$drLocation = "<disasterRecoveryLocation>"
$drServer = "<disasterRecoveryServerName>"
$failoverGroup = "<globallyUniqueFailoverGroupName>"

# create a backup server in the failover region
New-AzSqlServer -ResourceGroupName $resourceGroup -ServerName $drServer `
    -Location $drLocation -SqlAdministratorCredentials $(New-Object -TypeName System.Management.Automation.PSCredential `
    -ArgumentList $admin, $(ConvertTo-SecureString -String $password -AsPlainText -Force))

# create a failover group between the servers
New-AzSqlDatabaseFailoverGroup -ResourceGroupName $resourceGroup -ServerName $server `
    -PartnerServerName $drServer -FailoverGroupName $failoverGroup -FailoverPolicy Automatic -GracePeriodWithDataLossHours 2

# add the database to the failover group
Get-AzSqlDatabase -ResourceGroupName $resourceGroup -ServerName $server -DatabaseName $database | `
    Add-AzSqlDatabaseToFailoverGroup -ResourceGroupName $resourceGroup -ServerName $server -FailoverGroupName $failoverGroup

$admin = "<adminName>"
$password = "<password>"
$resourceGroup = "<resourceGroupName>"
$location = "<resourceGroupLocation>"
$server = "<serverName>"
$database = "<databaseName>"
$drLocation = "<disasterRecoveryLocation>" # must be different then $location
$drServer = "<disasterRecoveryServerName>"
$failoverGroup = "<globallyUniqueFailoverGroupName>"

# create a backup server in the failover region
az sql server create --admin-password $password --admin-user $admin `
    --name $drServer --resource-group $resourceGroup --location $drLocation

# create a failover group between the servers
az sql failover-group create --name $failoverGroup --partner-server $drServer `
    --resource-group $resourceGroup --server $server --add-db $database `
    --failover-policy Automatic --grace-period 2

Geo-replication settings can also be changed in the Azure portal, by selecting your database, then Settings > Geo-Replication.

Run the sample project

1. In the console, create a Maven project with the following command:

   mvn archetype:generate "-DgroupId=com.sqldbsamples" "-DartifactId=SqlDbSample" "-DarchetypeArtifactId=maven-archetype-quickstart" "-Dversion=1.0.0"
   

2. Type Y and press Enter.

3. Change directories to the new project.

   cd SqlDbSample
   

4. Using your favorite editor, open the pom.xml file in your project folder.

5. Add the Microsoft JDBC Driver for SQL Server dependency by adding the following dependency section. The dependency must be pasted within the larger dependencies section.

   <dependency>
     <groupId>com.microsoft.sqlserver</groupId>
     <artifactId>mssql-jdbc</artifactId>
    <version>6.1.0.jre8</version>
   </dependency>
   

6. Specify the Java version by adding the properties section after the dependencies section:

   <properties>
     <maven.compiler.source>1.8</maven.compiler.source>
     <maven.compiler.target>1.8</maven.compiler.target>
   </properties>
   

7. Support manifest files by adding the build section after the properties section:

   <build>
     <plugins>
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-jar-plugin</artifactId>
         <version>3.0.0</version>
         <configuration>
           <archive>
             <manifest>
               <mainClass>com.sqldbsamples.App</mainClass>
             </manifest>
           </archive>
        </configuration>
       </plugin>
     </plugins>
   </build>
   

8. Save and close the pom.xml file.

9. Open the App.java file located in ..\SqlDbSample\src\main\java\com\sqldbsamples and replace the contents with the following code:

   package com.sqldbsamples;
   
   import java.sql.Connection;
   import java.sql.Statement;
   import java.sql.PreparedStatement;
   import java.sql.ResultSet;
   import java.sql.Timestamp;
   import java.sql.DriverManager;
   import java.util.Date;
   import java.util.concurrent.TimeUnit;
   
   public class App {
   
      private static final String FAILOVER_GROUP_NAME = "<your failover group name>";  // add failover group name
   
      private static final String DB_NAME = "<your database>";  // add database name
      private static final String USER = "<your admin>";  // add database user
      private static final String PASSWORD = "<your password>";  // add database password
   
      private static final String READ_WRITE_URL = String.format("jdbc:" +
         "sqlserver://%s.database.chinacloudapi.cn:1433;database=%s;user=%s;password=%s;encrypt=true;" +
         "hostNameInCertificate=*.database.chinacloudapi.cn;loginTimeout=30;", +
         FAILOVER_GROUP_NAME, DB_NAME, USER, PASSWORD);
      private static final String READ_ONLY_URL = String.format("jdbc:" +
         "sqlserver://%s.secondary.database.chinacloudapi.cn:1433;database=%s;user=%s;password=%s;encrypt=true;" +
         "hostNameInCertificate=*.database.chinacloudapi.cn;loginTimeout=30;", +
         FAILOVER_GROUP_NAME, DB_NAME, USER, PASSWORD);
   
      public static void main(String[] args) {
         System.out.println("#######################################");
         System.out.println("## GEO DISTRIBUTED DATABASE TUTORIAL ##");
         System.out.println("#######################################");
         System.out.println("");
   
         int highWaterMark = getHighWaterMarkId();
   
         try {
            for(int i = 1; i < 1000; i++) {
                //  loop will run for about 1 hour
                System.out.print(i + ": insert on primary " +
                   (insertData((highWaterMark + i)) ? "successful" : "failed"));
                TimeUnit.SECONDS.sleep(1);
                System.out.print(", read from secondary " +
                   (selectData((highWaterMark + i)) ? "successful" : "failed") + "\n");
                TimeUnit.SECONDS.sleep(3);
            }
         } catch(Exception e) {
            e.printStackTrace();
      }
   }
   
   private static boolean insertData(int id) {
      // Insert data into the product table with a unique product name so we can find the product again
      String sql = "INSERT INTO SalesLT.Product " +
         "(Name, ProductNumber, Color, StandardCost, ListPrice, SellStartDate) VALUES (?,?,?,?,?,?);";
   
      try (Connection connection = DriverManager.getConnection(READ_WRITE_URL);
              PreparedStatement pstmt = connection.prepareStatement(sql)) {
         pstmt.setString(1, "BrandNewProduct" + id);
         pstmt.setInt(2, 200989 + id + 10000);
         pstmt.setString(3, "Blue");
         pstmt.setDouble(4, 75.00);
         pstmt.setDouble(5, 89.99);
         pstmt.setTimestamp(6, new Timestamp(new Date().getTime()));
         return (1 == pstmt.executeUpdate());
      } catch (Exception e) {
         return false;
      }
   }
   
   private static boolean selectData(int id) {
      // Query the data previously inserted into the primary database from the geo replicated database
      String sql = "SELECT Name, Color, ListPrice FROM SalesLT.Product WHERE Name = ?";
   
      try (Connection connection = DriverManager.getConnection(READ_ONLY_URL);
              PreparedStatement pstmt = connection.prepareStatement(sql)) {
         pstmt.setString(1, "BrandNewProduct" + id);
         try (ResultSet resultSet = pstmt.executeQuery()) {
            return resultSet.next();
         }
      } catch (Exception e) {
         return false;
      }
   }
   
   private static int getHighWaterMarkId() {
      // Query the high water mark id stored in the table to be able to make unique inserts
      String sql = "SELECT MAX(ProductId) FROM SalesLT.Product";
      int result = 1;
      try (Connection connection = DriverManager.getConnection(READ_WRITE_URL);
              Statement stmt = connection.createStatement();
              ResultSet resultSet = stmt.executeQuery(sql)) {
         if (resultSet.next()) {
             result =  resultSet.getInt(1);
            }
         } catch (Exception e) {
          e.printStackTrace();
         }
         return result;
      }
   }
   

10. Save and close the App.java file.

11. In the command console, run the following command:

    mvn package
    

12. Start the application that will run for about 1 hour until stopped manually, allowing you time to run the failover test.

    mvn -q -e exec:java "-Dexec.mainClass=com.sqldbsamples.App"
    

    #######################################
    ## GEO DISTRIBUTED DATABASE TUTORIAL ##
    #######################################
    
    1. insert on primary successful, read from secondary successful
    2. insert on primary successful, read from secondary successful
    3. insert on primary successful, read from secondary successful
    ...
    

Test failover

Run the following scripts to simulate a failover and observe the application results. Notice how some inserts and selects will fail during the database migration.

(Get-AzSqlDatabaseFailoverGroup -FailoverGroupName $failoverGroup `
    -ResourceGroupName $resourceGroup -ServerName $drServer).ReplicationRole

az sql failover-group show --name $failoverGroup --resource-group $resourceGroup --server $drServer

Next steps

Review the high availability and disaster recovery checklist.

Related Azure SQL Database content:

• Business continuity with
• High availability
• Failover groups
• Active geo-replication