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Multi-tenant using multiple Schemas


In this post we will see how to create a multi-tenant application using one schema by tenant. The idea is to create one CodeFluent Entities model and use it to generate as many database schemas as needed.

The generated database will contains one schema by tenant:

But to keep the usage as simple as possible, only one Business Object Model is generated. The schema is selected at runtime:

Note: The following procedure uses the Custom meta-compiler host feature which is available only with CodeFluent Entities Personal or Ultimate

Generate the database

 

The idea is to keep the model untouched, so we create a console application which:

  • Load the CodeFluent Entities model
  • Change entity schema in memory (the original model won’t be changed)
  • Generate code
class Program
{
    private static string _schema;
    private static string _projectPath;
    private static bool _changeTargetDirectory;

    static void Main()
    {
        _projectPath = CommandLineUtilities.GetArgument("path", (string)null) ?? CommandLineUtilities.GetArgument(0, (string)null);
        _schema = ConvertUtilities.Nullify(CommandLineUtilities.GetArgument("schema", (string)null) ?? CommandLineUtilities.GetArgument(1, (string)null), true);
        _changeTargetDirectory = CommandLineUtilities.GetArgument("changeTargetDirectory", true);

        // Load the model
        Project project = new Project();
        project.Entities.ListChanged += Entities_ListChanged; // Change schema as soon as the entity is loaded
        project.Load(_projectPath, ProjectLoadOptions.Default);

        // Update producer target directory
        if (!string.IsNullOrEmpty(_schema) && _changeTargetDirectory)
        {
            foreach (var producer in project.Producers)
            {
                var sqlServerProducer = producer.Instance as SqlServerProducer;
                if (sqlServerProducer != null)
                {
                    sqlServerProducer.Production += SqlServerProducer_Production;
                }
            }
        }

        // Generate code
        project.Produce();
    }

    private static readonly HashSet<IProducer> _producers = new HashSet<IProducer>();
    private static void SqlServerProducer_Production(object sender, ProductionEventArgs e)
    {
        SqlServerProducer sqlServerProducer = sender as SqlServerProducer;
        if (sqlServerProducer == null)
            return;

        if (_producers.Contains(sqlServerProducer))
            return;

        sqlServerProducer.EditorTargetDirectory = Path.Combine(sqlServerProducer.EditorTargetDirectory, _schema);
        _producers.Add(sqlServerProducer);
    }

    private static void Entities_ListChanged(object sender, ListChangedEventArgs e)
    {
        if (e.ListChangedType != ListChangedType.ItemAdded)
            return;

        var entityCollection = sender as EntityCollection;
        if (entityCollection == null || e.NewIndex < 0 || e.NewIndex >= entityCollection.Count)
            return;

        Entity entity = entityCollection[e.NewIndex];
        Console.WriteLine("Changing schema of entity '{0}' from '{1}' to '{2}'", entity.ClrFullTypeName, entity.Schema, _schema);
        entity.Schema = _schema;
    }
}

That’s it… We can now use this console application to generate the persistence layer:

SoftFluent.MultiTenantGenerator.exe "Sample.Model\Sample.Model.cfxproj" "SoftFluent"
SoftFluent.MultiTenantGenerator.exe "Sample.Model\Sample.Model.cfxproj" "Contoso"

You can create a script to call program this for each tenant.

Select the right tenant at runtime

 

We generate only one Business Object Model (BOM) for all tenants. This BOM access by default to the schema specified in the CodeFluent Entities model. In our case we want to change this schema at runtime depending on the context (user, Uri, etc.).

To access the database, the generated code use CodeFluentPersistence:

CodeFluentPersistence has a hook system (ICodeFluentPersistenceHook) that allows to change the default CodeFluentPersistence behavior. In our case the idea is to change the CreateStoredProcedureCommand method behavior to use the right schema. Here’s the code:

public class SchemaPersistenceHook : BasePersistenceHook
{
    private bool _processing = false;
    public override bool BeforeCreateStoredProcedureCommand(string schema, string package, string intraPackageName, string name)
    {
        if (_processing)
            return false;

        _processing = true;
        try
        {
            string currentSchema = GetTenant();
            Persistence.CreateStoredProcedureCommand(currentSchema, package, intraPackageName, name);
        }
        finally
        {
            _processing = false;
        }

        return true;
    }

    public virtual string GetTenant()
    {
            // TODO: Implement your own logic
            return CodeFluentUser.Current.UserDomainName;
    }
}

Finally we have to declare our persistence hook in the configuration file so CodeFluentPersistence will use it automatically:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <configSections>
    <section name="Sample" type="CodeFluent.Runtime.CodeFluentConfigurationSectionHandler, CodeFluent.Runtime" />
  </configSections>

  <Sample persistenceHookTypeName="Sample.SchemaPersistenceHook, Sample" />
</configuration>

That’s it. With a few lines of codes and the power of CodeFluent Entities you can change the default behavior to fit your needs. Can you do the same with other products?

The source code is available on our GitHub repository.

Happy tenanting,

The R&D team

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