writer.json

OLake supports two writer modes for exporting your database data in Parquet format:

1. Local Parquet Writer
2. S3 Writer
3. Iceberg Writer (coming soon)

Before proceeding with either configuration, please ensure you have completed the getting started instructions for the database you want to connect from. For more background details, refer to the README section.

Iceberg

Apache Iceberg

The Iceberg Writer syncs data from databases (MySQL, MongoDB, PostgreSQL) into Apache Iceberg.

AWS Glue

writer.json

{
    "type": "ICEBERG",
    "writer": {
      "normalization": false,
      "s3_path": "s3://bucket_name/olake_iceberg/test_olake",
      "aws_region": "ap-south-1",
      "aws_access_key": "XXX",
      "aws_secret_key": "XXX",
      "database": "olake_iceberg",
      "grpc_port": 50051,
      "server_host": "localhost"
    }
}

JDBC + MinIO Local

writer.json

{
  "type": "ICEBERG",
  "writer": {
    "catalog_type": "jdbc",
    "jdbc_url": "jdbc:postgresql://localhost:5432/iceberg",
    "jdbc_username": "iceberg",
    "jdbc_password": "password",
    "normalization": false,
    "iceberg_s3_path": "s3a://warehouse",
    "s3_endpoint": "http://localhost:9000",
    "s3_use_ssl": false,
    "s3_path_style": true,
    "aws_access_key": "admin",
    "aws_secret_key": "password",
    "iceberg_db": "olake_iceberg"
  }
}

For sample configuration and other details regarding Apache Iceberg, refer to Iceberg writer docs.

S3

S3 Writer

OLake’s Parquet S3 writer allows you to write your data directly into an Amazon S3 bucket in Parquet format. This mode is ideal for users who want to leverage S3’s scalable storage for their data outputs.

writer.json

{
  "type": "PARQUET",
  "writer": {
    "normalization": false,
    "s3_bucket": "olake-s3-test",
    "s3_region": "ap-south-1",
    "s3_access_key": "xxxxxxxxxxxxxxxxxxxx",
    "s3_secret_key": "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
    "s3_path": "/data"
  }
}

Key	Description	Data Type	Probable Values
type	Specifies the output file format for writing data. Currently, only the "PARQUET" format is supported.	string	"PARQUET"
writer.normalization	Indicates whether data normalization (JSON flattening) should be applied before writing data to S3. Use true if you require normalized output, or false if not.	boolean	true or false (this example uses false)
writer.s3_bucket	The name of the Amazon S3 bucket where your output files will be stored. Ensure that the bucket exists and that you have proper access.	string	A valid S3 bucket name (e.g. "olake-s3-test")
writer.s3_region	The AWS region where the specified S3 bucket is hosted.	string	AWS region codes such as "ap-south-1", "us-west-2", etc.
writer.s3_access_key	The AWS access key used for authenticating S3 requests. This is typically a 20-character alphanumeric string.	string	A valid AWS access key
writer.s3_secret_key	The AWS secret key used for S3 authentication. This key is generally longer (often 40+ characters) and should be kept secure.	string	A valid AWS secret key
writer.s3_path	The specific path (or prefix) within the S3 bucket where data files will be written. This is typically a folder path that starts with a / (e.g. "/data").	string	A valid path string

info

1. The generated .parquet files use SNAPPY compression (Read more). Note that SNAPPY is no longer supported by S3 Select when performing queries.
2. OLake creates a test folder named olake_writer_test containing a single text file (.txt) with the content:

   S3 write test
   This is used to verify that you have the necessary permissions to write to S3.

For sample configuration and other details regarding S3, refer to S3 writer docs.

Local

Local Parquet Writer

The local writer mode is used to write Parquet files directly to a local directory inside your Docker container. The local directory is mapped to your host file system via a Docker volume. To run OLake via docker, follow getting started guide.

Sample Configuration

writer.json

{
  "type": "PARQUET",
  "writer": {
    "normalization": false,
    "local_path": "./mnt/config"
  }
}

Configuration Key Details

Key	Data Type	Example Value	Description & Possible Values
type	string	"PARQUET"	Specifies the output file format. Currently, only the Parquet format is supported.
writer.normalization	boolean	false	Determines whether OLake applies level-1 JSON flattening to nested objects. Set to true if you require normalized output; otherwise, use false.
writer.local_path	string	"/mnt/config"	The local directory inside the Docker container where Parquet files will be stored. This path is mapped to your host file system via a Docker volume.

Note: This configuration enables the Parquet local writer. For more details, check out the README section.

For sample configuration and other details regarding local writer, refer to S3 writer docs.