Destination PostgreSQL #

The extracted replicant-cli will be referred to as the $REPLICANT_HOME directory in the following steps.

Required permissions #

Make sure that the user being used for replication, has the CREATE TABLE privilege on the target catalogs or schemas where you want to replicate the tables to. Use the following command to grant the privileges:
```
GRANT CREATE ON DATABASE <catalog_name> TO <replication_user>;
```
Replace the following:
- catalog_name: the catalog name in the target
- replication_user: the user being used for replication
In order to store Arcion’s replication metadata, you must ensure one of the following:
- Point to an external metadata database. For more information, see Metadata configuration.
- Grant the CREATEDB privilege to the user being used for replication. This allows the user to create the io database. The user must also possess the privilege to create tables in the io database. Replicant uses this io database to maintain internal checkpoint and metadata.
The following command assigns the CREATEDB privilege to a user alex:
```
ALTER USER alex CREATEDB;
```
If the user does not have CREATEDB privilege, then follow these two steps:
1. Create a database manually with the name io:
```
CREATE DATABASE io;
```
2. Grant all privileges for the io database to that user:
```
GRANT ALL ON DATABASE io TO alex;
```

I. Set up connection configuration #

To connect to your PostgreSQL target database, you have these two options:

Use a connection configuration file

You can specify your connection details to Replicant with a YAML connection configuration file. You can find a sample connection configuration file cloudsql_postgresql.yaml in the $REPLICANT_HOME/conf/conn directory.

type: POSTGRESQL

host: HOSTNAME
port: PORT_NUMBER

database: 'DATABASE_NAME' 
username: 'USERNAME'
password: 'PASSWORD'

max-connections: 30
socket-timeout-s: 60
max-retries: 10
retry-wait-duration-ms: 1000

Replace the following:

HOSTNAME: the hostname of the target PostgreSQL instance
PORT_NUMBER: the port number
DATABASE_NAME: the database name
USERNAME: the username of the user that connects to the PostgreSQL server
PASSWORD: the password associated with USERNAME

Feel free to change the following parameter values as you need:

max-connections: the maximum number of connections Replicant opens in Cloud SQL instance.
max-retries: number of times Replicant retries a failed operation.
retry-wait-duration-ms: duration in milliseconds Replicant waits between each retry of a failed operation.
socket-timeout-s: the timeout value in seconds specifying socket read operations. A value of 0 disables socket reads. This parameter is only supported for Arcion self-hosted CLI versions 22.02.12.16 and newer.

Important: Make sure that max_connections in PostgreSQL exceeds the max-connections parameter in the preceding connection configuration file.

Use a secrets management service

You can store your connection credentials in a secrets management service and tell Replicant to retrieve the credentials. For more information, see Secrets management.

II. Configure mapper file (optional) #

If you want to define data mapping from source to your target PostgreSQL, specify the mapping rules in the mapper file. The following is a sample mapper configuration for a MySQL-to-PostgreSQL pipeline:

rules:
  [tpch, public]:
    source:
    - [tpch]

For more information on how to define the mapping rules and run Replicant CLI with the mapper file, see Mapper configuration.

III. Set up Applier configuration #

To configure replication mode according to your requirements, specify your configuration in the Applier configuration file. You can find a sample Applier configuration file postgresql.yaml in the $REPLICANT_HOME/conf/dst directory. For example:

You can configure PostgreSQL for operating in either snapshot or realtime modes.

Configure `snapshot` mode #

For operating in snapshot mode, specify your configuration under the snapshot section of the conifiguration file. For example:

snapshot:
  threads: 16
  batch-size-rows: 5_000
  txn-size-rows: 1_000_000
  skip-tables-on-failures: false

  map-bit-to-boolean: false

  bulk-load:
    enable: true
    type: FILE # FILE or PIPE

  _traceDBTasks: true
  use-quoted-identifiers: true

Additional `snapshot` parameters #

map-bit-to-boolean

Tells Replicant whether to map bit(1) and varbit(1) data types from source to boolean on target.

If true, Replicant maps bit(1)/varbit(1) data types from source to boolean on target PostgreSQL. If false, Replicant maps bit(1)/varbit(1) data types from source to bit(1)/varbit(1) on target PostgreSQL.

Default: false.

For more information about the Applier parameters for snapshot mode, see Snapshot mode.

Configure `realtime` mode #

If you want to operate in real time, use the realtime section to specify your configuration. For example:

realtime:
  threads: 8
  txn-size-rows: 10000
  batch-size-rows: 1000
  skip-tables-on-failures : false

  use-quoted-identifiers: true

For more information about the configuration parameters for realtime mode, see Realtime mode.