# Connecting to the Data Catalog using Amazon Glue Iceberg REST endpoint


 Amazon Glue's Iceberg REST endpoint supports API operations specified in the Apache Iceberg REST specification. Using an Iceberg REST client, you can connect your application running on an analytics engine to the REST catalog hosted in the Data Catalog.

 The endpoint supports both Apache Iceberg table specifications - v1 and v2, defaulting to v2. When using the Iceberg table v1 specification, you must specify v1 in the API call. Using the API operation, you can access Iceberg tables stored in both Amazon S3 object storage and Amazon S3 Table storage. 

**Endpoint configuration**

You can access the Amazon Glue Iceberg REST catalog using the service endpoint. Refer to the [Amazon Glue service endpoints reference guide](https://docs.aws.amazon.com/general/latest/gr/glue.html#glue_region) for the region-specific endpoint. For example, when connecting to Amazon Glue in the us-east-1 Region, you need to configure the endpoint URI property as follows: 

```
Endpoint : https://glue.us-east-1.amazonaws.com/iceberg
```

** Additional configuration properties** – When using Iceberg client to connect an analytics engine like Spark to the service endpoint, you are required to specify the following application configuration properties:

```
catalog_name = "mydatacatalog"
aws_account_id = "123456789012"
aws_region = "us-east-1"
spark = SparkSession.builder \
    ... \
    .config("spark.sql.defaultCatalog", catalog_name) \
    .config(f"spark.sql.catalog.{catalog_name}", "org.apache.iceberg.spark.SparkCatalog") \
    .config(f"spark.sql.catalog.{catalog_name}.type", "rest") \
    .config(f"spark.sql.catalog.{catalog_name}.uri", "https://glue.{aws_region}.amazonaws.com/iceberg") \
    .config(f"spark.sql.catalog.{catalog_name}.warehouse", "{aws_account_id}") \
    .config(f"spark.sql.catalog.{catalog_name}.rest.sigv4-enabled", "true") \
    .config(f"spark.sql.catalog.{catalog_name}.rest.signing-name", "glue") \    
    .config("spark.sql.extensions","org.apache.iceberg.spark.extensions.IcebergSparkSessionExtensions") \
    .getOrCreate()
```

Amazon Glue Iceberg endpoint ` https://glue.us-east-1.amazonaws.com/iceberg` supports supports the following Iceberg REST APIs:
+ GetConfig
+ ListNamespaces
+ CreateNamespace
+ LoadNamespaceMetadata
+ UpdateNamespaceProperties
+ DeleteNamespace
+ ListTables
+ CreateTable
+ LoadTable
+ TableExists
+ UpdateTable
+ DeleteTable

## Prefix and catalog path parameters


Iceberg REST catalog APIs have a free-form prefix in their request URLs. For example, the `ListNamespaces` API call uses the `GET/v1/{prefix}/namespaces` URL format. Amazon Glue prefix always follows the `/catalogs/{catalog}` structure to ensure that the REST path aligns the Amazon Glue multi-catalog hierarchy. The `{catalog}` path parameter can be derived based on the following rules:


| **Access pattern** |  **Glue catalog ID Style**  |  **Prefix Style**  | **Example default catalog ID** |  **Example REST route**  | 
| --- | --- | --- | --- | --- | 
|  Access the default catalog in current account  | not required | : |  not applicable  |  GET /v1/catalogs/:/namespaces  | 
|  Access the default catalog in a specific account  | accountID | accountID | 111122223333 | GET /v1/catalogs/111122223333/namespaces | 
|  Access a nested catalog in current account  |  catalog1/catalog2  |  catalog1/catalog2  |  rmscatalog1:db1  |  GET /v1/catalogs/rmscatalog1:db1/namespaces  | 
|  Access a nested catalog in a specific account  |  accountId:catalog1/catalog2  |  accountId:catalog1/catalog2  |  123456789012/rmscatalog1:db1  |  GET /v1/catalogs/123456789012:rmscatalog1:db1/namespaces  | 

This catalog ID to prefix mapping is required only when you directly call the REST APIs. When you are working with the Amazon Glue Iceberg REST catalog APIs through an engine, you need to specify the Amazon Glue catalog ID in the `warehouse` parameter for your Iceberg REST catalog API setting or in the `glue.id` parameter for your Amazon Glue extensions API setting. For example, see how you can use it with EMR Spark in [Use an Iceberg cluster with Spark](https://docs.aws.amazon.com/emr/latest/ReleaseGuide/emr-iceberg-use-spark-cluster.html).

## Namespace path parameter


Namespaces in Iceberg REST catalog APIs path can have multiple levels. However, Amazon Glue only supports single-level namespaces. To access a namespace in a multi-level catalog hierarchy, you can connect to a multi-level catalog above the namespace to reference the namespace. This allows any query engine that supports the 3-part notation of `catalog.namespace.table` to access objects in Amazon Glue’s multi-level catalog hierarchy without compatibility issues compared to using the multi-level namespace.