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

Article
12/15/2023

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

Create a failover group
Run a Java application to query a database in SQL Database
Test failover

If you don't have an Azure subscription, create a free account before you begin.

Prerequisites

Note

This article uses the Azure Az PowerShell module, which is the recommended PowerShell module for interacting with Azure. To get started with the Az PowerShell module, see Install Azure PowerShell. To learn how to migrate to the Az PowerShell module, see Migrate Azure PowerShell from AzureRM to Az.

Important

The PowerShell Azure Resource Manager module is still supported by Azure SQL Database, but all future development is for the Az.Sql module. For these cmdlets, see AzureRM.Sql. The arguments for the commands in the Az module and in the AzureRm modules are substantially identical.

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,
Note

The tutorial uses the AdventureWorksLT sample database.

Important

Be sure to set up firewall rules to use the public IP address of the computer on which you're performing the steps in this tutorial. Database-level firewall rules will replicate automatically to the secondary server.

For information see Create a database-level firewall rule or to determine the IP address used for the server-level firewall rule for your computer see Create a server-level firewall.

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.

PowerShell
The Azure CLI

Important

This sample requires Azure PowerShell Az 1.0 or later. Run Get-Module -ListAvailable Az to see which versions are installed. If you need to install, see Install Azure PowerShell module.

Run Connect-AzAccount to sign in to Azure.

To create a failover group, run the following script:

$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

Important

Run az login to sign in to Azure.

$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.

Geo-replication settings

Run the sample project

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"

Type Y and press Enter.
Change directories to the new project.
```
cd SqlDbSample
```
Using your favorite editor, open the pom.xml file in your project folder.
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>
```

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>

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>

Save and close the pom.xml file.

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 = "<password>";  // add database password

   private static final String READ_WRITE_URL = String.format("jdbc:" +
      "sqlserver://%s.database.windows.net:1433;database=%s;user=%s;password=%s;encrypt=true;" +
      "hostNameInCertificate=*.database.windows.net;loginTimeout=30;",
      FAILOVER_GROUP_NAME, DB_NAME, USER, PASSWORD);
   private static final String READ_ONLY_URL = String.format("jdbc:" +
      "sqlserver://%s.secondary.database.windows.net:1433;database=%s;user=%s;password=%s;encrypt=true;" +
      "hostNameInCertificate=*.database.windows.net;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;
   }
}

Save and close the App.java file.
In the command console, run the following command:
```
mvn package
```

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.

PowerShell
The Azure CLI

You can check the role of the disaster recovery server during the test with the following command:

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

To test a failover:

Start a manual failover of the failover group:

Switch-AzSqlDatabaseFailoverGroup -ResourceGroupName $resourceGroup `
 -ServerName $drServer -FailoverGroupName $failoverGroup

Revert failover group back to the primary server:

Switch-AzSqlDatabaseFailoverGroup -ResourceGroupName $resourceGroup `
 -ServerName $server -FailoverGroupName $failoverGroup

You can check the role of the disaster recovery server during the test with the following command:

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

To test a failover:

Start a manual failover of the failover group:

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

Revert failover group back to the primary server:

az sql failover-group set-primary --name $failoverGroup --resource-group $resourceGroup --server $server

Next steps

Review the high availability and disaster recovery checklist.

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

Prerequisites

Create a failover group

Run the sample project

Test failover

Next steps

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Additional resources