Jeff's thoughts on Software Architecture, Large Scale Services and the Technical world at large : SDS

SDS Java JDBC examples

jcurrier — Sun, 29 Mar 2009 23:57:00 GMT

In my previous blog entry I mentioned that I would post some Java & JDBC examples for connecting to and interacting with the SDS service. Since that post (roughly an hour ago) I’ve been called a, “slacker” by David Robinson one of the PM’s on the team. Therefore, to show that I am not a, “slacker” I’ve decided to just post the code today. Happy Dave :-)

So, in this example I’m using Java 1.6, NetBeans as the editor and the latest JDBC driver for SQL Server which you can download from here. The only jar file I’m currently using to compile (and run with) other than the expected JRE jar files is the, “sqljdbc4.jar” jar file which comes along with the download I’ve linked to above. NOTE: That if you choose to use an earlier version of JDBC it *must* support SSL. This is a requirement for the service.

Now, I’ve purposely made this example to be the exact same as the C# example I did previously so you could focus more on the differences with the client technologies and less on the actual data I’ve created. As you can see the only significant difference relative to SDS is the format of a couple of connection string values (namely the database, user id format and the initial url for the server). Other than that it’s the same code that we would use to connect to locally.

Now, with no further delay. The Java code for working with SDS.

    public static void main(String[] args)
    {
        String createTableSql = 
                "CREATE TABLE [dbo].[tbl_Person]    " +
                "(                                                    " +
                "     [FirstName] NVARCHAR(64) NOT NULL,              " +
	            "     [LastName] NVARCHAR(64) NOT NULL                " +
                "    CONSTRAINT [personName_PK] PRIMARY KEY CLUSTERED " +
                "    (                                                " +
                "        [FirstName] ASC,                             " +
                "        [LastName] ASC                               " +
                "    )                                                " +
                ")";     
        
        String insertSql = 
                "INSERT INTO dbo.tbl_Person(FirstName, LastName) VALUES ('Jeff', 'Currier'); " +
                "INSERT INTO dbo.tbl_Person(FirstName, LastName) VALUES ('Nigel', 'Ellis'); " +
                "INSERT INTO dbo.tbl_Person(FirstName, LastName) VALUES ('David', 'Robinson');"+ 
                "INSERT INTO dbo.tbl_Person(FirstName, LastName) VALUES ('Jeff', 'Smith');";
                
        try
        {
            // First, format the connection string note that the server name here again is, “myserver”.  The database name (my user database name) is mydatabase.  
            String connectionUrl = "jdbc:sqlserver://myserver.data.dev.mscds.com;" +
                    "database=mydatabase;encrypt=true;user=jeff@myserver;password=*****";

            // Next, make the sure the SQL Server Driver is loaded.
            Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
            
            // Then attempt to get a connection.  This will null or throw if we can't
            // get a connection.
            Connection sqlConn = DriverManager.getConnection(connectionUrl);
            if (sqlConn == null)
            {
                System.out.println("Unable to obtain connection.  exiting");
                System.exit(1);
            }

            // Begin by creating the table we'll use.
            Statement sqlStmt = sqlConn.createStatement();
            sqlStmt.execute(createTableSql);

            // Then, insert some rows into the table that we just created.
            sqlStmt.execute(insertSql);

            // Now, select all of the, "Jeff' data from the table and print them out.
            ResultSet results = sqlStmt.executeQuery("select FirstName, LastName from tbl_Person where FirstName='Jeff'");
            while (results.next())
            {
                System.out.println("FirstName: " + results.getString("FirstName") + " LastName: " + results.getString("LastName"));
            }
            // Close the ResultSet up.
            results.close();

            // Finally drop the table and close the conneciton.
            sqlStmt.execute("drop table tbl_Person");
            sqlConn.close();
        } catch (SQLException ex)
        {
            System.out.println("Error: Unable to execute query ");
            ex.printStackTrace();
        } catch(ClassNotFoundException ex)
        {
            System.out.println("Error: Unable to load JDBC Driver!");
        }

    }

Enjoy,

--Jeff--

SDS coding examples – Part 1 (C# & ADO.NET)

jcurrier — Sun, 29 Mar 2009 23:16:00 GMT

So, as I did with the original SDS I want to outline some code examples that other developers can use to get a sense of how to interact with the service. In general, this will be much easier now that we have shifted more to the relational model as some of the more abstract (okay maybe not sooo abstract) concepts don’t necessarily need to be explained from scratch. Having said that, there are a few concepts that are worth covering before we dive into the code.

Servers, and Masters, and User Databases, oh my!

There are really two different types of databases that we have present in SDS now. The first, and the one that you’ll generally interact with the most, is the user database. This is really where your user data resides. You’re in charge in this space. You define the tables, schemas and what have you that appear in this database. We may insert some data into locked down tables (and present them to you with views) here to help assist you with debugging and provide some metrics data but by in large this is your house. NOTE: The name you choose here for your user database (“mydatabase” in the example below) is the name of the database you specify in the connection string.

connStringBuilder.InitialCatalog = "mydatabase"; // Specify your user database to connect to.

The second type of database is really what we refer to as the logical master database (or server database) but it actually encapsulates two different things. The first thing is that the server represents a logical master database. This is the database where we keep track of all of the user databases that you have on this logical server. It’s important to note that this is *not* a real server and is more logical in nature. We will also store things your metrics here as well as login information NOTE: Because we store login information here this is why you have specify your server name in the user id as certain elements don’t come across in the initial TDS packets we receive.

The second important thing to note about the server database is that is associated (along with each of the user databases managed by it) with a particular geo-location. You will pick the geo-location when you go through the provisioning process and requests will be routed to your servers by taking advantage of the DNS system as once done previously. The code snippet below illustrates how the server presents itself in the connection string.

connStringBuilder.DataSource = "myserver.data.dev.mscds.com"; // Specify the DNS name of my SDS server (which holds my master db).
connStringBuilder.UserID = "jeff@myserver";                   // Specify my user id (and the server name which holds my master db)

On to the code

So now with no further delay is some sample code. It’s simple (on purpose) but it illustrates the types of operations that you’ll be able to do (DDL & DML). In this example, I simply create a table, insert some rows, select some rows from that table, and finally drop the table in the end. Here you go! If you have other questions around the code please feel free to comment and I’ll try to reply as soon as I can.

        static void Main(string[] args)
        {
            // Begin, by constructing the connection string using the SqlConnectionStringBuilder class for
            // simplicity.  I could just use String.Format but this makes it a bit easier to explain what
            // we're doing with each parameter.

            SqlConnectionStringBuilder connStringBuilder = new SqlConnectionStringBuilder();
            connStringBuilder.DataSource = "myserver.data.dev.mscds.com"; // Specify the DNS name of my SDS server (which holds my master db).
            connStringBuilder.InitialCatalog = "mydatabase";              // Specify your user database to connect to.
            connStringBuilder.Encrypt = true;                             // Specify that I would like the channel to be encrypted.
            connStringBuilder.UserID = "jeff@myserver";                   // Specify my user id (and the server name which holds my master db)
            connStringBuilder.Password = "****";                          // Finally, specify my password.

            string createTableSql =
                @"CREATE TABLE [dbo].[tbl_Person]
                (
                     [FirstName] NVARCHAR(64) NOT NULL,
	             [LastName] NVARCHAR(64) NOT NULL
                    CONSTRAINT [personName_PK] PRIMARY KEY CLUSTERED
                    (
                        [FirstName] ASC,
                        [LastName] ASC
                    )
                )";

            string insertSql =
                @"INSERT INTO dbo.tbl_Person(FirstName, LastName) VALUES ('Jeff', 'Currier');
                  INSERT INTO dbo.tbl_Person(FirstName, LastName) VALUES ('Nigel', 'Ellis');
                  INSERT INTO dbo.tbl_Person(FirstName, LastName) VALUES ('David', 'Robinson');
                  INSERT INTO dbo.tbl_Person(FirstName, LastName) VALUES ('Jeff', 'Smith');";
            try
            {
                // New up a connection to my previously provisioned user database just as I would to any other database.
                // and then open it.
                using (SqlConnection conn = new SqlConnection(connStringBuilder.ToString()))
                {
                    conn.Open();

                    // Construct a new SqlCommand object that we'll use to execute execute our Sql code.
                    using (SqlCommand cmd = conn.CreateCommand())
                    {
                        // Use the above defined SQL to create a simple table that we'll to construct a table for this
                        // example
                        cmd.CommandText = createTableSql;
                        cmd.CommandType = CommandType.Text;
                        cmd.ExecuteNonQuery();

                        // Insert some simple data into that table.
                        cmd.CommandText = insertSql;
                        cmd.CommandType = CommandType.Text;
                        cmd.ExecuteNonQuery();

                        // Next, perform a simple select finding all of the persons in the table whose first name is Jeff.
                        cmd.CommandText = "select FirstName, LastName from dbo.tbl_Person where FirstName = 'Jeff'";
                        cmd.CommandType = CommandType.Text;
                        using (SqlDataReader reader = cmd.ExecuteReader())
                        {
                            while (reader.Read())
                            {
                                Console.WriteLine("First Name: {0} LastName: {1}", reader["FirstName"],
                                                  reader["LastName"]);
                            }

                            reader.Close();
                        }

                        // Finally, drop the table since we no longer need it.
                        cmd.CommandText = "Drop table dbo.tbl_Person";
                        cmd.CommandType = CommandType.Text;
                        cmd.ExecuteNonQuery();
                    }

                    conn.Close();
                }
            }
            catch (SqlException ex)
            {
                Console.WriteLine(ex);
            }
        }

Now, this example was in C# and used SqlClient (ADO.NET) but my next example will use Java & JDBC. If there are other languages (toolkits) you would like to see us illustrate please comment here or on the main SDS blog and we’ll try to get them out as soon as we can.

Enjoy!

--Jeff--

Check out Nigel's Talk on SDS from MIX09

jcurrier — Mon, 23 Mar 2009 05:09:56 GMT

Looks like the MIX folks have posted up Nigel's talk on the newly revamped SDS from MIX. You can watch it now here.

It’s been awhile…

jcurrier — Sat, 14 Mar 2009 23:51:06 GMT

So, it’s been quite awhile since I’ve posted but with the recent SDS announcement I trust you now know why that is. While I’ll be posting some code samples shortly for accessing the new SDS service via ADO.NET as well as with Java I’d like to give a plug for Nigel’s upcoming MIX09 talk on SDS.

I don’t want to steal any thunder from the talk next week so I’m going to hold off on talking much more about the service until after Nigel’s talk is completed. Keep posted though as you will see more details coming out from the team post MIX.

Finally, I’ve seen quite a bit of traffic in the blog community recently with concern that our new model doesn’t scale. I’ll just say this, we are all familiar with CAP conjecture, we do know what it takes to scale a relational store. We’ve done this once (with the initial version of Sitka which was built on the same technology) we will do it again. The larger question is getting the right application patterns in place so apps perform well on the system. That’s it for now but stay tuned.

SDS Channel 9 Video is up

jcurrier — Tue, 28 Oct 2008 06:27:00 GMT

A little while ago Jason and I recorded a Channel 9 video to discuss some of the newer features in SDS (SQL Data Services). Now that all the Azure components have been announced this is now available up at the Channel 9 site. You can view it here.