Connecting to Spark Connect using Clients

From the client perspective, Spark Connect mostly behaves as any other GRPC client and can be configured as such. However, to make it easy to use from different programming languages and to have a homogeneous connection surface this document proposes what the user surface is for connecting to a Spark Connect endpoint.

Background

Similar to JDBC or other database connections, Spark Connect leverages a connection string that contains the relevant parameters that are interpreted to connect to the Spark Connect endpoint

Connection String

Generally, the connection string follows the standard URI definitions. The URI scheme is fixed and set to sc://. The full URI has to be a valid URI and must be parsed properly by most systems. For example, hostnames have to be valid and cannot contain arbitrary characters. Configuration parameters are passed in the style of the HTTP URL Path Parameter Syntax. This is similar to the JDBC connection strings. The path component must be empty. All parameters are interpreted case sensitive.

text

sc://host:port/;param1=value;param2=value

<table> <tr> <td>Parameter</td> <td>Type</td> <td>Description</td> <td>Examples</td> </tr> <tr> <td>host</td> <td>String</td> <td> The hostname of the endpoint for Spark Connect. Since the endpoint has to be a fully GRPC compatible endpoint a particular path cannot be specified. The hostname must be fully qualified or can be an IP address as well. </td> <td> <pre>myexample.com</pre> <pre>127.0.0.1</pre> </td> </tr> <tr> <td>port</td> <td>Numeric</td> <td>The port to be used when connecting to the GRPC endpoint. The default value is: <b>15002</b>. Any valid port number can be used.</td> <td><pre>15002</pre><pre>443</pre></td> </tr> <tr> <td>token</td> <td>String</td> <td>When this param is set in the URL, it will enable standard bearer token authentication using GRPC. By default this value is not set. Setting this value enables SSL.</td> <td><pre>token=ABCDEFGH</pre></td> </tr> <tr> <td>use_ssl</td> <td>Boolean</td> <td>When this flag is set, will by default connect to the endpoint using TLS. The assumption is that the necessary certificates to verify the server certificates are available in the system. The default value is <b>false</b></td> <td><pre>use_ssl=true</pre><pre>use_ssl=false</pre></td> </tr> <tr> <td>user_id</td> <td>String</td> <td>User ID to automatically set in the Spark Connect UserContext message. This is necessary for the appropriate Spark Session management. This is an *optional* parameter and depending on the deployment this parameter might be automatically injected using other means.</td> <td> <pre>user_id=Martin</pre> </td> </tr> <tr> <td>user_agent</td> <td>String</td> <td>The user agent acting on behalf of the user, typically applications that use Spark Connect to implement its functionality and execute Spark requests on behalf of the user.

<i>Default: </i><pre>_SPARK_CONNECT_PYTHON</pre> in the Python client</td>
<td><pre>user_agent=my_data_query_app</pre></td>

</tr> <tr> <td>session_id</td> <td>String</td> <td>In addition to the user ID, the cache of Spark Sessions in the Spark Connect server uses a session ID as the cache key. This option in the connection string allows to provide this session ID to allow sharing Spark Sessions for the same users for example across multiple languages. The value must be provided in a valid UUID string format.

<i>Default: </i><pre>A UUID generated randomly</pre></td>
<td><pre>session_id=550e8400-e29b-41d4-a716-446655440000</pre></td>

</tr> <tr> <td>grpc_max_message_size</td> <td>Numeric</td> <td>Maximum message size allowed for gRPC messages in bytes.

<i>Default: </i><pre> 128 * 1024 * 1024</pre></td>
<td><pre>grpc_max_message_size=134217728</pre></td>

</tr> </table>

Examples

Valid Examples

Below we capture valid configuration examples, explaining how the connection string will be used when configuring the Spark Connect client.

The below example connects to port 15002 on myhost.com.

python

server_url = "sc://myhost.com/"

The next example configures the connection to use a different port with SSL.

python

server_url = "sc://myhost.com:443/;use_ssl=true"

python

server_url = "sc://myhost.com:443/;use_ssl=true;token=ABCDEFG"

Invalid Examples

As mentioned above, Spark Connect uses a regular GRPC client and the server path cannot be configured to remain compatible with the GRPC standard and HTTP. For example the following examples are invalid.

python

server_url = "sc://myhost.com:443/mypathprefix/;token=AAAAAAA"