Jump to: Postgres | MongoDB | MySQL

Postgres

Version compatibility: PowerSync requires Postgres version 11 or greater.
Configuring your Postgres database for PowerSync generally involves three tasks:
  1. Ensure logical replication is enabled
  2. Create a PowerSync database user
  3. Create powersync logical replication publication
We have documented steps for some hosting providers:
For other providers and self-hosted databases:

Unsupported Hosted Postgres Providers

Due to the logical replication requirement, not all Postgres hosting providers are supported. Notably, some “serverless Postgres” providers do not support logical replication, and are therefore not supported by PowerSync yet.

MongoDB

Version compatibility: PowerSync requires MongoDB version 6.0 or greater.

Permissions required - MongoDB Atlas

For MongoDB Atlas databases, the minimum permissions when using built-in roles are:
readWrite@<your_database>._powersync_checkpoints
read@<your_database>
To allow PowerSync to automatically enable changeStreamPreAndPostImages on replicated collections (the default for new PowerSync instances), additionally add the dbAdmin permission:
readWrite@<your_database>._powersync_checkpoints
read@<your_database>
dbAdmin@<your_database>
If you are replicating from multiple databases in the cluster, you need read permissions on the entire cluster, in addition to the above:
readAnyDatabase@admin

Privileges required - Self-hosted / Custom roles

For self-hosted MongoDB, or for creating custom roles on MongoDB Atlas, PowerSync requires the following privileges/granted actions:
  • On the database being replicated: listCollections
  • On all collections in the database: changeStream
    • This must apply to the entire database, not individual collections. Specify collection: ""
    • If replicating from multiple databases, this must apply to the entire cluster. Specify db: ""
  • On each collection being replicated: find
  • On the _powersync_checkpoints collection: createCollection, dropCollection, find, changeStream, insert, update, and remove
  • To allow PowerSync to automatically enable changeStreamPreAndPostImages on replicated collections, additionally add the collMod permission on all replicated collections.

Post-Images

To replicate data from MongoDB to PowerSync in a consistent manner, PowerSync uses Change Streams with post-images to get the complete document after each change. This requires the changeStreamPreAndPostImages option to be enabled on replicated collections. PowerSync supports three configuration options for post-images:
  1. Off: (post_images: off): Uses fullDocument: 'updateLookup' for backwards compatibility. This was the default for older instances. However, this may lead to consistency issues, so we strongly recommend enabling post-images instead.
  2. Automatic: (post_images: auto_configure) The default for new instances: Automatically enables the changeStreamPreAndPostImages option on collections as needed. Requires the permissions/privileges mentioned above. If a collection is removed from Sync Rules, developers can manually disable changeStreamPreAndPostImages.
  3. Read-only: (post_images: read_only): Uses fullDocument: 'required' and requires changeStreamPreAndPostImages: { enabled: true } to be set on every collection referenced in the Sync Rules. Replication will error if this is not configured. This option is ideal when permissions are restricted.
To manually configure collections for read_only mode, run this on each collection:
db.runCommand( {
 collMod: <collection>,
 changeStreamPreAndPostImages: { enabled: <boolean> }
} )
You can view which collections have the option enabled using:
db.getCollectionInfos().filter(c => c.options?.changeStreamPreAndPostImages?.enabled)
Post-images can be configured for PowerSync instances as follows:

PowerSync Cloud:

Configure the Post Images setting in the connection configuration in the Dashboard (right-click on your instance to edit it).

Self-Hosted PowerSync:

Configure post_images in the config.yaml file.
If you need to use private endpoints with MongoDB Atlas, see Private Endpoints (AWS only).

Migrating from MongoDB Atlas Device Sync

For more information on migrating from Atlas Device Sync to PowerSync, see our migration guide.

MySQL (Beta)

Version compatibility: PowerSync requires MySQL version 5.7 or greater.
PowerSync reads from the MySQL binary log to replicate changes. We use a modified version of the Zongji MySQL binlog listener to achieve this.

Binlog Configuration

To ensure that PowerSync can read the binary log, you need to configure your MySQL server to enable binary logging and configure it with the following server command options:
  • server_id: Uniquely identifies the MySQL server instance in the replication topology. Default value is 1.
  • log_bin: ON. Enables binary logging. Default is ON for MySQL 8.0 and later, but OFF for MySQL 5.7.
  • enforce_gtid_consistency: ON. Enforces GTID consistency. Default is OFF.
  • gtid_mode: ON. Enables GTID based logging. Default is OFF.
  • binlog_format: ROW. Sets the binary log format to row-based replication. This is required for PowerSync to correctly replicate changes. Default is ROW.
These can be specified in a MySQL option file:
server_id=<Unique Integer Value>
log_bin=ON
enforce_gtid_consistency=ON
gtid_mode=ON
binlog_format=ROW

Database User Configuration

PowerSync also requires a MySQL user with REPLICATION and SELECT permission on the source databases. These can be added by running the following SQL commands:
-- Create a user with necessary privileges
CREATE USER 'repl_user'@'%' IDENTIFIED BY '<password>';

-- Grant replication client privilege
GRANT REPLICATION SLAVE, REPLICATION CLIENT ON *.* TO 'repl_user'@'%';

-- Grant select access to the specific database
GRANT SELECT ON <source_database>.* TO 'repl_user'@'%';

-- Apply changes
FLUSH PRIVILEGES;
It is possible to constrain the MySQL user further and limit access to specific tables. Care should be taken to ensure that all the tables in the sync rules are included in the grants.
-- Grant select to the users and the invoices tables in the source database
GRANT SELECT ON <source_database>.users TO 'repl_user'@'%';
GRANT SELECT ON <source_database>.invoices TO 'repl_user'@'%';

-- Apply changes
FLUSH PRIVILEGES;

Additional Configuration (optional)

Binlog

The binlog can be configured to limit logging to specific databases. By default, events for tables in all the databases on the MySQL server will be logged.
  • binlog-do-db: Only updates for tables in the specified database will be logged.
  • binlog-ignore-db: No updates for tables in the specified database will be logged.
Examples:
# Only row events for tables in the user_db and invoices_db databases will appear in the binlog.
binlog-do-db=user_db
binlog-do-db=invoices_db
# Row events for tables in the user_db will be ignored. Events for any other database will be logged.
binlog-ignore-db=user_db

Next Step

Next, connect PowerSync to your database: