DataWorks:Parameter node

Node introduction

Parameter nodes are virtual nodes that do not run computing tasks. Parameter nodes are used to pass parameters between nodes and manage parameters in workflows.

• Parameter passing between nodes

  If Node A in a workflow needs to obtain the output parameters of its ancestor nodes, you can create a parameter node and use the parameter node as an ancestor node of Node A and a descendant node of the ancestor nodes of Node A. Then, add all parameters required by Node A to the parameter node. This way, Node A can obtain all required parameters from the parameter node.

  

  In the preceding figure, the Sq_MySQL_G node needs to obtain the output parameters of the Sq_MySQL_B and Sq_MySQL_E nodes. A parameter node is created and used as the descendant node of the Sq_MySQL_B and Sq_MySQL_E nodes. All parameters required by the Sq_MySQL_G node are added to the parameter node. Then, the Sq_MySQL_G node is used as the descendant node to obtain the output parameters of the parameter node. The Sq_MySQL_G node can obtain all parameters of the Sq_MySQL_B and Sq_MySQL_E nodes by using the parameter node.

• Parameter management

  If nodes in a workflow need to use specific constant and variable parameters, you can create a parameter node and use the parameter node as the ancestor node of the nodes. Then, add all parameters required by the nodes to the parameter node. This way, the nodes can obtain all required parameters from the parameter node. The parameter node facilitates the centralized management of all parameters used in the workflow.

  

  In the preceding figure, the Sq2_MySQL_A, Sq2_MySQL_C, Sq2_MySQL_D, Sq2_MySQL_E, and Sq2_MySQL_F nodes need to use specific parameters. A parameter node is created and used as the ancestor node of the preceding nodes. You can use the parameter node to obtain the output parameters of the preceding nodes, and configure the corresponding variable parameters or constant parameters for the parameter node.

Prerequisites

• The RAM user that you want to use is added to your workspace.

  If you want to use a RAM user to develop tasks, you must add the RAM user to your workspace as a member and assign the Develop or Workspace Administrator role to the RAM user. The Workspace Administrator role has more permissions than necessary. Exercise caution when you assign the Workspace Administrator role. For more information about how to add a member and assign roles to the member, see Add workspace members and assign roles to them.

• A serverless resource group is associated with your workspace. For more information, see the topics in the Use serverless resource groups directory.

• A parameter node is created before you develop a task on the parameter node. For more information, see Create a task node.

Precautions

If a node needs to use parameters in a parameter node, the node must be a direct descendant node of the parameter node.

Step 1: Use a parameter node to develop a task

You can add a parameter of the Constant, Variable, or Pass-through Variable type in the parameter node. The following tabs describe how to add the preceding types of parameters.

After you configure parameters for the parameter node, configure scheduling properties for the node. For more information.

Step 2: Use the parameters in the parameter node

After you configure the parameter node, the descendant nodes of the parameter node can directly use the parameters in the parameter node. This facilitates the centralized management of parameters and improves the task development efficiency of descendant nodes.

1. Associate the parameters of the ancestor node with the parameter node.

   1. In the right-side navigation of the configuration tab of the parameter node, click Properties. On the Properties tab, click Scheduling Dependencies. In the Node Dependencies section of the Scheduling Dependencies tab, click Add Dependency to configure the parameter node as an upstream dependency.

      

   2. After you configure the dependency, go to the Scheduling Parameters section and click Add Parameter to add a parameter. The following table describes the parameters.

      1. Specify a name for the parameter.

      2. Click the icon to search for the output parameters of the ancestor nodes of the parameter node and associate the output parameters with the parameter node.

         

2. After you configure the parameters, you can use ${Parameter name} to obtain and use the parameters passed from the parameter node when you modify the node script.

Step 2: Deploy the parameter node and perform O&M operations

1. After the node code and scheduling properties are configured, deploy the parameter node and its ancestor and descendant nodes to the production environment. For more information, see Node or workflow deployment.

2. After the deployment is complete, go to the Auto Triggered Nodes page in Operation Center to view the node that is deployed and perform O&M operations on the node. The system periodically runs the node based on the scheduling properties that you configure. For more information, see Getting started with Operation Center.