Amazon PostgreSQL RDS

Connecting PostgreSQL RDS

PostgreSQL RDS Setup Requirements

To set up PostgreSQL RDS in Stitch, you need:

• Permissions in Amazon Web Services (AWS) that allow you to:

  • Create/manage Security Groups, which is required to whitelist Stitch’s IP addresses.
  • View database details, which is required for retrieving the database’s connection details.

• Permissions in PostgreSQL RDS that allow you to create/manage users. This is required to create the Stitch database user.

• To verify if the database is a read replica, or follower. While we always recommend connecting a replica over a production database, this also means you may need to verify some of its settings - specifically the standby settings - before connecting it to Stitch.

  On occasion, the default values for the standby settings can prevent Stitch from successfully completing queries, resulting in slow, intermittent replication. This is usually only an issue during historical syncs or when replicating large amounts of data (ex: a large table using Full Table Replication).

  If you find that the hot_standby setting is on, proactively increasing the following settings from 30 seconds to 8-12 hours can help prevent this issue:

  • max_standby_archive_delay
  • max_standby_streaming_delay

  After the initial historical sync completes, you can typically decrease these settings again.

  For an official explanation of these settings, check out the Postgres docs.

Step 1: Whitelist Stitch's IP addresses

For Stitch to successfully connect with your RDS instance, you’ll need to add our IP addresses to the appropriate database security group via the AWS management console. To do this, an inbound security rule must be created for each of our IP addresses.

The IP addresses can be added to an existing group or you can create a new one. The important thing is that the group is authorized to access the instance you want to connect to Stitch.

1. Log into your AWS account.
2. Navigate to the Security Group Management page, typically Services > Compute > EC2.
3. Click the Security Groups option, under Network & Security in the menu on the left side of the page.
4. Click Create Security Group.
5. In the window that displays, fill in the fields as follows:
   • Security group name: Enter a unique name for the security group. For example: Stitch
   • Description: Enter a description for the security group.
   • VPC: Verify that the selected VPC is the same VPC your database is in.
6. In the Inbound tab, click Add Rule.
7. Fill in the fields as follows:
   • Type: Select Custom TCP Rule
   • Port Range: Enter the port your database uses. (5432 by default)

   • CIDR, IP or Security Group, enter one of the IP addresses listed below:

     • 52.23.137.21/32

     • 52.204.223.208/32

     • 52.204.228.32/32

     • 52.204.230.227/32

8. Add another rule by clicking the Add Rule button.

9. Repeat steps 6-8 until all the IP addresses above have been added:

   

10. When finished, click Create.

Step 2: Retrieve your Stitch Public Key

The Public Key is used to authorize the Stitch Linux user. If the key isn’t properly installed, Stitch will be unable to access your database.

To retrieve the key:

1. Sign into your Stitch account.

2. On the Stitch Dashboard page, click the Add Integration button.

3. Click the PostgreSQL icon.

4. When the credentials page displays, click the Encryption Type menu and select the SSH Tunnel option.

5. The Public Key will display, along with the other SSH fields.

Leave this page open for now - you’ll need it to wrap things up at the end.

Step 3: Create a Stitch Linux user

Note: Anything inside square brackets - [like this] - is something you need to define when running the commands yourself.

1. To create the new user, run the following commands as root on your Linux server:

   adduser --disabled-password [stitch_username]
   mkdir /home/[stitch_username]/.ssh
   

2. Next, import the Public Key into authorized_keys. This will ensure the Stitch user has access to the database.

   Copy the entire key into the authorized_keys file by:

   "[PASTE KEY HERE]" >> /home/[stitch_username]/.ssh/authorized_keys
   

3. Alter the permissions on the /home/[stitch_username] directory to allow access via SSH:

   chown -R [stitch_username]:[stitch_username] /home/[stitch_username]
   chmod -R 700 /home/[stitch_username]/.ssh
   

Step 4: Create a Stitch database user

Next, you’ll create a dedicated database user for Stitch. This will ensure Stitch is visible in any logs or audits, and allow you to maintain your privilege hierarchy.

• Instructions
• Privileges list

CREATE USER [stitch_username] WITH ENCRYPTED PASSWORD '[secure password]';
GRANT CONNECT ON DATABASE [database_name] TO [stitch_username];
GRANT USAGE ON SCHEMA [schema_name] TO [stitch_username];
GRANT SELECT ON ALL TABLES IN SCHEMA [schema_name] TO [stitch_username];
ALTER DEFAULT PRIVILEGES IN SCHEMA [schema_name] GRANT SELECT ON TABLES TO [stitch_username];

Step 5: Locate RDS connection details in AWS

Next, you’ll retrieve the connection details required to complete the setup in Stitch. This info can be found on the Instance Details page in AWS.

If you don’t still have this page open, click Instances and then the instance you’re connecting to Stitch.

1. On the Instance Details page, scroll down to the Connect section.

2. Locate the Endpoint and Port fields, which are highlighted in the image below:

   

Leave this page open for now - you’ll need it to complete the setup in the next step.

Step 6: Connect Stitch

1. Sign into your Stitch account, if you haven’t already.
2. On the Stitch Dashboard page, click the Add Integration button.
3. Click the PostgreSQL icon.

4. Fill in the fields as follows:

   • Integration Name: Enter a name for the integration. This is the name that will display on the Stitch Dashboard for the integration; it’ll also be used to create the schema in your data warehouse.

     For example, the name “Stitch PostgreSQL RDS” would create a schema called stitch_postgresql_rds in the data warehouse. Note: The schema name cannot be changed after the integration is saved.

   • Host (Endpoint): Paste the Endpoint address from the PostgreSQL RDS Details page in AWS into this field.
     
     Don’t include the port number, which is appended to the end of the endpoint string - this will cause errors.

   • Port: Enter the port used by the PostgreSQL RDS instance. The default is 5432.

   • Username: Enter the Stitch PostgreSQL RDS database user’s username.

   • Password: Enter the password for the Stitch database user.

   • Database: Enter the name of the PostgreSQL RDS database. Stitch will ‘find’ all databases you give the Stitch user access to - a default database is only used to complete the connection. This is required for PostgreSQL RDS integrations.

Enter SSH Connection Details

If you’re using an SSH tunnel to connect your PostgreSQL RDS database to Stitch, you’ll also need to complete the following:

1. Click the Encryption Type menu.

2. Select SSH Tunnel to display the SSH fields.

3. Fill in the fields as follows:

   • Remote Address: Enter the IP address or hostname of the server Stitch will SSH into.

   • SSH Port: Enter the SSH port on your server. (22 by default)

   • SSH User: Enter the Stitch Linux (SSH) user’s username.

In addition, click the Connect using SSL checkbox if you’re using an SSL connection. Note: The database must support and allow SSL connections for this setting to work correctly.

Step 7: Create a replication schedule

In the Replication Frequency section, you’ll create the integration’s replication schedule. An integration’s replication schedule determines how often Stitch runs a replication job, and the time that job begins.

Stitch offers two methods of creating a replication schedule:

• Replication Frequency: This method requires selecting the interval you want replication to run for the integration. Start times of replication jobs are based on the start time and duration of the previous job. Refer to the Replication Frequency documentation for more information and examples.

• Anchor scheduling: Based on the Replication Frequency, or interval, you select, this method “anchors” the start times of this integration’s replication jobs to a time you select to create a predictable schedule. Anchor scheduling is a combination of the Anchor Time and Replication Frequency settings, which must both be defined to use this method. Additionally, note that:

  • A Replication Frequency of at least one hour is required to use anchor scheduling.

  • An initial replication job may not begin immediately after saving the integration, depending on the selected Replication Frequency and Anchor Time. Refer to the Anchor Scheduling documentation for more information.

  • You’ll need to contact support to request using an Anchor Time with this integration.

To help prevent overages, consider setting the integration to replicate less frequently. See the Understanding and Reducing Your Row Usage guide for tips on reducing your usage.

Step 8: Select data to replicate

The last step is to select the tables and columns you want to replicate. When you track a table, you’ll also need to define its Replication Method and, if using Key-based Incremental Replication, its Replication Key.

You can track tables and columns by:

1. In the Integration Details page, click the Tables to Replicate tab.
2. Locate a table you want to replicate.
3. Click the checkbox next to the object’s name. A green checkmark means the object is set to replicate.
4. If there are child objects, they’ll automatically display and you’ll be prompted to select some.
5. After you set a table to replicate, the Table Settings page will display. Note: When you track a table, by default all columns will also be tracked.

6. In the Table Settings page, define the table’s Replication Method and, if using Key-based Incremental Replication, its Replication Key.

7. Repeat this process for every table you want to replicate.

Initial and historical replication jobs

After you finish setting up PostgreSQL RDS, its Sync Status may show as Pending on either the Stitch Dashboard or in the Integration Details page.

For a new integration, a Pending status indicates that Stitch is in the process of scheduling the initial replication job for the integration. This may take some time to complete.

Free historical data loads

The first seven days of replication, beginning when data is first replicated, are free. Rows replicated from the new integration during this time won’t count towards your quota. Stitch offers this as a way of testing new integrations, measuring usage, and ensuring historical data volumes don’t quickly consume your quota.

Extracting data from PostgreSQL RDS

When you connect a database as an input, Stitch only needs read-only access to the databases, tables, and columns you want to replicate. There are two processes Stitch runs during the Extraction phase of the replication process: a structure sync and a data sync.

Structure sync queries

The first part of the replication process is called a structure sync. This process will detect any changes to the structure of your database. For example: a new column is added to one of the tables you’re syncing in Stitch.

To perform a structure sync, Stitch runs queries on the following tables in the pg_catalog schema:

• pg_class
• pg_attribute
• pg_index
• pg_namespace

Data sync queries

The second step in the Extraction phase is called a data sync. This is where Stitch extracts data and replicates it. The method Stitch uses is the same for all databases, but differs depending on the Replication Method that each table uses.

Key-based Incremental Replication

For tables using Key-based Incremental Replication, Stitch runs a single query and reads out of the associated cursor in batches:

  SELECT column_a, column_b <,...>
    FROM table_a
   WHERE replication_key_column >= 'last_maximum_replication_key_value'
ORDER BY replication_key_column

Full Table Replication

For tables using Full Table Replication, Stitch runs a single query and reads out of the resulting cursor in batches:

SELECT column_a, column_b <,...>
  FROM table_a

Recommendations

While we make every effort to ensure the queries that Stitch executes don’t impart significant load on your databases, we still have some recommendations for guaranteeing database performance:

• Use a replica database instead of connecting directly. We recommend using read replicas in lieu of directly connecting production databases with high availability and performance requirements.
• Apply indexes to Replication Key columns. We restrict and order our replication queries by this column, so applying an index to the columns you’re using as Replication Keys can improve performance.

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