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Mssql

Calabi Connect's certified MSSQL connector offers the following features:

⚠️ Please note the minimum required platform version is v0.58.0 to run source-mssql 4.0.18 and above.

Features​

FeatureSupportedNotes
Full Refresh SyncYes
Incremental Sync - AppendYes
Replicate Incremental DeletesYes
CDC (Change Data Capture)Yes
SSL SupportYes
SSH Tunnel ConnectionYes
NamespacesYesEnabled by default

The MSSQL source does not alter the schema present in your database. Depending on the destination connected to this source, however, the schema may be altered. See the destination's documentation for more details.

Getting Started​

Requirements​

  1. MSSQL Server Azure SQL Database, Azure Synapse Analytics, Azure SQL Managed Instance, SQL Server 2022, SQL Server 2019, SQL Server 2017, SQL Server 2016, SQL Server 2014, SQL Server 2012, PDW 2008R2 AU34.
  2. Create a dedicated read-only Calabi Connect user with access to all tables needed for replication
  3. If you want to use CDC, please see the relevant section below for further setup requirements

1. Make sure your database is accessible from the machine running Calabi Connect​

This is dependent on your networking setup. The easiest way to verify if Calabi Connect is able to connect to your MSSQL instance is via the check connection tool in the UI.

This step is optional but highly recommended to allow for better permission control and auditing. Alternatively, you can use Calabi Connect with an existing user in your database.

3. Your database user should now be ready for use with Calabi Connect!​

Calabi Connect​

On Calabi Connect, only secured connections to your MSSQL instance are supported in source configuration. You may either configure your connection using one of the supported SSL Methods or by using an SSH Tunnel.

Change Data Capture (CDC)​

We use SQL Server's change data capture feature with transaction logs to capture row-level INSERT, UPDATE and DELETE operations that occur on CDC-enabled tables.

Some extra setup requiring at least db_owner permissions on the database(s) you intend to sync from will be required (detailed below).

Please read the CDC docs for an overview of how Calabi Connect approaches CDC.

Should I use CDC for MSSQL?​

  • If you need a record of deletions and can accept the limitations posted below, CDC is the way to go!
  • If your data set is small and/or you just want a snapshot of your table in the destination, consider using Full Refresh replication for your table instead of CDC.
  • If the limitations below prevent you from using CDC and your goal is to maintain a snapshot of your table in the destination, consider using non-CDC incremental and occasionally reset the data and re-sync.
  • If your table has a primary key but doesn't have a reasonable cursor field for incremental syncing (i.e. updated_at), CDC allows you to sync your table incrementally.

CDC Limitations​

  • Make sure to read our CDC docs to see limitations that impact all databases using CDC replication.
  • hierarchyid and sql_variant types are not processed in CDC migration type (not supported by Debezium). For more details please check this ticket
  • CDC is only available for SQL Server 2016 Service Pack 1 (SP1) and later.
  • db_owner (or higher) permissions are required to perform the necessary setup for CDC.
  • On Linux, CDC is not supported on versions earlier than SQL Server 2017 CU18 (SQL Server 2019 is supported).
  • Change data capture cannot be enabled on tables with a clustered columnstore index. (It can be enabled on tables with a non-clustered columnstore index).
  • The SQL Server CDC feature processes changes that occur in user-created tables only. You cannot enable CDC on the SQL Server master database.
  • Using variables with partition switching on databases or tables with change data capture (CDC) is not supported for the ALTER TABLE ... SWITCH TO ... PARTITION ... statement.
  • CDC incremental syncing is only available for tables with at least one primary key. Tables without primary keys can still be replicated by CDC but only in Full Refresh mode. For more information on CDC limitations, refer to our CDC Limitations doc.
  • Our CDC implementation uses at least once delivery for all change records.
  • Read more on CDC limitations in the Microsoft docs.

Setting up CDC for MSSQL​

1. Enable CDC on database and tables​

MS SQL Server provides some built-in stored procedures to enable CDC.

  • To enable CDC, a SQL Server administrator with the necessary privileges (db_owner or sysadmin) must first run a query to enable CDC at the database level.

    USE {database name}
    GO
    EXEC sys.sp_cdc_enable_db
    GO

  • The administrator must then enable CDC for each table that you want to capture. Here's an example:

    USE {database name}
    GO

    EXEC sys.sp_cdc_enable_table
    @source_schema = N'{schema name}',
    @source_name   = N'{table name}',
    @role_name     = N'{role name}',  [1]
    @filegroup_name = N'{filegroup name}', [2]
    @supports_net_changes = 0 [3]
    GO
    • [1] Specifies a role which will gain SELECT permission on the captured columns of the source table. We suggest putting a value here so you can use this role in the next step but you can also set the value of @rolename to NULL to allow only _sysadmin and db_owner to have access. Be sure that the credentials used to connect to the source in Calabi Connect align with this role so that Calabi Connect can access the cdc tables.
    • [2] Specifies the filegroup where SQL Server places the change table. We recommend creating a separate filegroup for CDC but you can leave this parameter out to use the default filegroup.
    • [3] If 0, only the support functions to query for all changes are generated. If 1, the functions that are needed to query for net changes are also generated. If supports_net_changes is set to 1, index_name must be specified, or the source table must have a defined primary key.

  • (For more details on parameters, see the Microsoft doc page for this stored procedure).

  • If you have many tables to enable CDC on and would like to avoid having to run this query one-by-one for every table, this script might help!

For further detail, see the Microsoft docs on enabling and disabling CDC.

2. Enable snapshot isolation​

  • When a sync runs for the first time using CDC, Calabi Connect performs an initial consistent snapshot of your database. To avoid acquiring table locks, Calabi Connect uses snapshot isolation, allowing simultaneous writes by other database clients. This must be enabled on the database like so:

    ALTER DATABASE {database name}
      SET ALLOW_SNAPSHOT_ISOLATION ON;

3. Create a user and grant appropriate permissions​

  • Rather than use sysadmin or db_owner credentials, we recommend creating a new user with the relevant CDC access for use with Calabi Connect. First let's create the login and user and add to the db_datareader role:

    USE {database name};
    CREATE LOGIN {user name}
      WITH PASSWORD = '{password}';
    CREATE USER {user name} FOR LOGIN {user name};
    EXEC sp_addrolemember 'db_datareader', '{user name}';

    • Add the user to the role specified earlier when enabling cdc on the table(s):

      EXEC sp_addrolemember '{role name}', '{user name}';

    • This should be enough access, but if you run into problems, try also directly granting the user SELECT access on the cdc schema:

      USE {database name};
      GRANT SELECT ON SCHEMA :: [cdc] TO {user name};

    • If feasible, granting this user 'VIEW SERVER STATE' permissions will allow Calabi Connect to check whether or not the SQL Server Agent is running. This is preferred as it ensures syncs will fail if the CDC tables are not being updated by the Agent in the source database.

      USE master;
      GRANT VIEW SERVER STATE TO {user name};

4. Extend the retention period of CDC data​

  • In SQL Server, by default, only three days of data are retained in the change tables. Unless you are running very frequent syncs, we suggest increasing this retention so that in case of a failure in sync or if the sync is paused, there is still some bandwidth to start from the last point in incremental sync.

  • These settings can be changed using the stored procedure sys.sp_cdc_change_job as below:

    -- we recommend 14400 minutes (10 days) as retention period
    EXEC sp_cdc_change_job @job_type='cleanup', @retention = {minutes}

  • After making this change, a restart of the cleanup job is required:

  EXEC sys.sp_cdc_stop_job @job_type = 'cleanup';

  EXEC sys.sp_cdc_start_job @job_type = 'cleanup';
  • If you are using Transaction Replication, the retention has to be changed using the following scripts:

EXEC sp_changedistributiondb
  @database = 'distribution',
  @property = 'max_distretention',
  @value = 14400 -- 14400 minutes (10 days)

EXEC sp_changedistributiondb
  @database = 'distribution',
  @property = 'history_retention',
  @value = 14400 -- 14400 minutes (10 days)

USE [msdb]
GO
EXEC msdb.dbo.sp_update_jobstep @job_name=N'Distribution clean up: distribution', @step_id=1 ,
		@command=N'EXEC dbo.sp_MSdistribution_cleanup @min_distretention = 0, @max_distretention = 14400'
GO

5. Ensure the SQL Server Agent is running​

  • MSSQL uses the SQL Server Agent to run the jobs necessary for CDC. It is therefore vital that the Agent is operational in order for CDC to work effectively. You can check the status of the SQL Server Agent as follows:
  EXEC xp_servicecontrol 'QueryState', N'SQLServerAGENT';
  • If you see something other than 'Running.' please follow the Microsoft docs to start the service.

Connection to MSSQL via an SSH Tunnel​

Calabi Connect has the ability to connect to a MSSQL instance via an SSH Tunnel. The reason you might want to do this because it is not possible (or against security policy) to connect to the database directly (e.g. it does not have a public IP address).

When using an SSH tunnel, you are configuring Calabi Connect to connect to an intermediate server (a.k.a. a bastion server) that does have direct access to the database. Calabi Connect connects to the bastion and then asks the bastion to connect directly to the server.

Using this feature requires additional configuration, when creating the source. We will talk through what each piece of configuration means.

  1. Configure all fields for the source as you normally would, except SSH Tunnel Method.

  2. SSH Tunnel Method defaults to No Tunnel (meaning a direct connection). If you want to use an

    SSH Tunnel choose SSH Key Authentication or Password Authentication.

    1. Choose Key Authentication if you will be using an RSA private key as your secret for

      establishing the SSH Tunnel (see below for more information on generating this key).

    2. Choose Password Authentication if you will be using a password as your secret for establishing

      the SSH Tunnel.

  3. SSH Tunnel Jump Server Host refers to the intermediate (bastion) server that Calabi Connect will connect to. This should

    be a hostname or an IP Address.

  4. SSH Connection Port is the port on the bastion server with which to make the SSH connection. The default port for

    SSH connections is 22, so unless you have explicitly changed something, go with the default.

  5. SSH Login Username is the username that Calabi Connect should use when connecting to the bastion server. This is NOT the

    MSSQL username.

  6. If you are using Password Authentication, then SSH Login Username should be set to the

    password of the User from the previous step. If you are using SSH Key Authentication leave this

    blank. Again, this is not the MSSQL password, but the password for the OS-user that Calabi Connect is

    using to perform commands on the bastion.

  7. If you are using SSH Key Authentication, then SSH Private Key should be set to the RSA

    private Key that you are using to create the SSH connection. This should be the full contents of

    the key file starting with -----BEGIN RSA PRIVATE KEY----- and ending

    with -----END RSA PRIVATE KEY-----.

Generating an SSH Key Pair​

The connector expects an RSA key in PEM format. To generate this key:

ssh-keygen -t rsa -m PEM -f myuser_rsa

This produces the private key in pem format, and the public key remains in the standard format used by the authorized_keys file on your bastion host. The public key should be added to your bastion host to whichever user you want to use with Calabi Connect. The private key is provided via copy-and-paste to the Calabi Connect connector configuration screen, so it may log in to the bastion.

Data type mapping​

MSSQL data types are mapped to the following data types when synchronizing data. You can check the test values examples here. If you can't find the data type you are looking for or have any problems feel free to add a new test!

MSSQL TypeResulting TypeNotes
bigintnumber
binarystring
bitboolean
charstring
datedate
datetimetimestamp
datetime2timestamp
datetimeoffsettimestamp with timezone
decimalnumber
intnumber
floatnumber
geographystring
geometrystring
moneynumber
numericnumber
ntextstring
nvarcharstring
nvarchar(max)string
realnumber
smalldatetimetimestamp
smallintnumber
smallmoneynumber
sql_variantstring
uniqueidentifierstring
textstring
timetime
tinyintnumber
varbinarystring
varcharstring
varchar(max) COLLATE Latin1_General_100_CI_AI_SC_UTF8string
xmlstring

If you do not see a type in this list, assume that it is coerced into a string. We are happy to take feedback on preferred mappings.

Upgrading to version 4.3.0 and above​

Version 4.3.0 introduces a migration from the legacy CDK to the new CDK architecture. This migration includes:

  • Automatic State Migration: The connector automatically migrates legacy version 2 state formats to the new version 3 format. This includes:
    • OrderedColumnLoadStatus (primary key-based initial sync) → version 3 primary_key state type
    • CursorBasedStatus (cursor-based incremental) → version 3 cursor_based state type
  • Backward Compatibility: Existing connections will continue to work seamlessly without any manual intervention

Upgrading from 0.4.17 and older versions to 0.4.18 and newer versions​

There is a backwards incompatible spec change between Microsoft SQL Source connector versions 0.4.17 and 0.4.18. As part of that spec change replication_method configuration parameter was changed to object from string.

In Microsoft SQL source connector versions 0.4.17 and older, replication_method configuration parameter was saved in the configuration database as follows:

"replication_method": "STANDARD"

Starting with version 0.4.18, replication_method configuration parameter is saved as follows:

"replication_method": {
    "method": "STANDARD"
}

After upgrading Microsoft SQL Source connector from 0.4.17 or older version to 0.4.18 or newer version you need to fix source configurations in the actor table in Calabi Connect database. To do so, you need to run two SQL queries. Follow the instructions in Calabi Connect documentation to run SQL queries on Calabi Connect database.

If you have connections with Microsoft SQL Source using Standard replication method, run this SQL:

update public.actor set configuration =jsonb_set(configuration, '{replication_method}', '{"method": "STANDARD"}', true)
WHERE actor_definition_id ='b5ea17b1-f170-46dc-bc31-cc744ca984c1' AND (configuration->>'replication_method' = 'STANDARD');

If you have connections with Microsoft SQL Source using Logical Replication (CDC) method, run this SQL:

update public.actor set configuration =jsonb_set(configuration, '{replication_method}', '{"method": "CDC"}', true)
WHERE actor_definition_id ='b5ea17b1-f170-46dc-bc31-cc744ca984c1' AND (configuration->>'replication_method' = 'CDC');