Creating a Flow

Prerequisites

• You have created a function. For details, see Creating a Function from Scratch.
• You have understood the components, orchestration rules, and expression operators.

Procedure

1. Log in to the FunctionGraph console, and choose Flows in the navigation pane.
2. On the Function Flows page, click Create next to Standard Flow or Express Flow.
   

   Function flows created on OBS DWR cannot be edited or deleted on the FunctionGraph console. If you need to do so, go to OBS DWR.

3. Orchestrate a flow for your application.
   1. Orchestrate the flow by dragging components.
      Take the flow in Figure 1 as an example. Drag a start node, function, and stop node to the edit box, and connect them using lines.

      Figure 1 Orchestrating a flow
      
   2. Click the function node to edit it. For details about the function parameters, see Table 1. Parameters marked with an asterisk (*) are mandatory.
      

      For the function node, select function 2, and configure this node by referring to Figure 2. The result will be the value of the event input plus 2.

      Figure 2 Configuring a function node
      

      Table 1 Function parameters

      Parameter	Description
      * App	App to which the desired function belongs. You can create multiple functions under an app.
      * Function	Function you want to use. NOTE: The data returned by the configured function must be in JSON format. Otherwise, it cannot be parsed. Go functions can return stream data. To enable this feature, choose Configuration > Advanced Settings on the function details page, and select Streaming Response.
      * Version	Function version you want to use.
      * CallMode	By default, function nodes in a flow are invoked synchronously. NOTE: Synchronous invocation does not support long-term running functions and is max. 15 minutes. Asynchronous invocation supports long-term running functions. The max. duration of a function node is the same as that supported by FunctionGraph.
      Function Parameters	Parameters that will be passed in JSON format in the body. Key: parameter name Value: parameter value DefaultValue: used if no value is specified for the parameter Operation: Edit or delete the parameter.
      Input Filter Expression	Selects part of the JSON output of the previous step to use it as the input of the current step.
      Output Filter Expression	Selects part of the JSON output of the current step to pass it to the next step.

   3. Click the EG node to edit it. For details about the EG parameters, see Table 2. Parameters marked with an asterisk (*) are mandatory.
      

      Before configuring an EG node, ensure that you have created an event source and channel on EG. For details, see Figure 3.

      Figure 3 Configuring an EG node
      

      Table 2 EG node parameters

      Parameter	Description
      * Event Channel	Event channels receive events from event sources. Function flows support only custom event channels, which you create to receive events from custom sources. For details, see the event channel description in the EG documentation.
      * Source	Event sources are applications that produce events. Function flows support only custom application event sources, which publish events to EG through a custom channel. For details, see the event source description in the EG documentation.
      DataContentType	The format of Data, that is, event payload. NOTE: Only application/json is supported.
      Data	Event content.
      Subject	A subject or object on which an event occurs.
      Input Filter Expression	Selects part of the JSON output of the previous step to use it as the input of the current step.
      Output Filter Expression	Selects part of the JSON output of the current step to pass it to the next step.

   4. Configure processors by referring to Table 3. Parameters marked with an asterisk (*) are mandatory.

      Table 3 Processor parameters

      Category	Parameter	Description
      Callback	* Callback timeout (min)	If no response is returned within the specified timeout, the node fails.
      	* Callback Type	Type of the service node that can be called back by a function flow. NOTE: Only function nodes are supported.
      	* App	App to which the desired function belongs. You can create multiple functions under an app.
      	* Function	Function you want to use. NOTE: The data returned by the configured function must be in JSON format. Otherwise, the data cannot be parsed. Go functions can return stream data. To enable this feature, choose Configuration > Advanced Settings on the function details page, and select Streaming Response.
      	* Version	Function version you want to use.
      	* CallMode	By default, function nodes in a flow are invoked synchronously. NOTE: Synchronous invocation does not support long-term running functions and is max. 15 minutes. Asynchronous invocation supports long-term running functions. The max. duration of a function node is the same as that supported by FunctionGraph.
      	Function Parameters	Parameters that will be passed in JSON format in the body. Key: parameter name Value: parameter value DefaultValue: used if no value is specified for the parameter Operation: Edit or delete the parameter.
      	Input Filter Expression	Selects part of the JSON output of the previous step to use it as the input of the current step.
      	Output Filter Expression	Selects part of the JSON output of the current step to pass it to the next step.
      Subflow	Subflow	Select a flow.
      	Proceed Until Subflow Completed	This option is enabled by default.
      	Input Filter Expression	Selects part of the JSON output of the previous step to use it as the input of the current step.
      	Output Filter Expression	Selects part of the JSON output of the current step to pass it to the next step.
      Parallel Branch	* Completion Criterion	All branches completed: suitable when there are two or more branches 1 branch completed: suitable when there is only one branch Set number of branches completed: suitable for one of the two or more branches if possible
      	Input Filter Expression	Selects part of the JSON output of the previous step to use it as the input of the current step.
      	Output Filter Expression	Selects part of the JSON output of the current step to pass it to the next step.
      	Set Branches	Set the number of branches that must be completed if you set Completion Criterion to Set number of branches completed.
      	* Result Output Path	Path to which the result of this parallel branch will be output in the JSON format. The path is a key and the result is a value. If this parameter is not set, the default path is result.
      Start	Triggers	Start of a flow. Each flow has only one start node. For details about how to create a trigger, see Creating a Flow Trigger.
      Error Handling	* Retry	Determines the next step in case of an execution failure. Retry Condition(JSONPath): Example: $.status == 500 Retry Interval (1-30s): The default value is 1s. Maximum Retries (1-8): The default value is 3.
      	* Retry Condition	A JSONPath expression. Result true indicates that an error is captured. The error handling node is executed then.
      Loop	* Array Path	Path of the array variable to be traversed.
      	* Iteration Variable	This variable will be replaced by the name of an element in the array during cyclic iteration.
      	* Result Output Path	Output path of the result array for all iteration branches.
      	Parallel Iterations	Number of iteration branches to be run concurrently. Value range: 0–100. 0 indicates unlimited.
      	Iteration Interval (s)	Interval between parallel iterations.
      	Input Filter Expression	Selects part of the JSON output of the previous step to use it as the input of the current step.
      	Output Filter Expression	Selects part of the JSON output of the current step to pass it to the next step.
      Wait	* Latency (s)	Default value: 1000s
      Service	Execution Mode	Way that functions in this node will be executed. Serial: Functions will be executed in the order they are connected. Parallel: Functions will be executed concurrently.
      	Input Filter Expression	JSONPath expression used to filter the input information of the node.
      	Output Filter Expression	JSONPath expression used to filter the output information of the node.
      Conditional Branch	* Branch Type	Conditional Default If there is a conditional branch, a default branch is required.
      	Expression	JSONPath expression required for a conditional branch. For details, see Expression Operators.
      	Input Filter Expression	JSONPath expression used to filter the input information of the node.
      	Output Filter Expression	JSONPath expression used to filter the output information of the node.
      Stop	Stop	Not followed by any other node.

   5. After configuring all nodes, click Save in the upper right corner.
      

      If a node in the flow is modified, save the changes before starting the flow.

   6. On the Create Flow page, click on the right of the function flow name in the upper left corner, set parameters, and click OK.

      Table 4 Configuration

      Parameter	Description
      * Name	Flow name.
      * Enterprise Project	Select an enterprise project.
      Combine Input	Whether to combine the previous node's output with the current node's input.
      Description	Description about the flow.

      Figure 4 Editing a flow
      
   7. Click Start. On the Start Execution page, specify input or start the flow directly. In this example, select With input.

      {
        "input":3
      }

      Figure 5 Starting execution
      
      

      The input values must be in JSON format.

   8. Click Execute. A message indicating that the flow is started successfully is displayed in the upper right corner.
   9. Click the flow name to go to the details page and view the execution result.