HTTP Poll

The HTTP_POLL is a conductor task used to invoke HTTP API until the specified condition matches.

Definitions

    {
      "name": "http_poll_task",
      "taskReferenceName": "http_poll_task_ref",
      "type": "HTTP_POLL",
      "inputParameters": {
        "http_request": {
          "uri": "https://orkes-api-tester.orkesconductor.com/get",
          "method": "GET",
          "connectionTimeOut": 3000,
          "readTimeOut": 3000,
          "accept": "application/json",
          "contentType": "application/json",
          "terminationCondition": "1",
          "pollingInterval": "60",
          "pollingStrategy": "FIXED"
        }
      }
    }

Input Parameters

Attribute	Description
terminalCondition	Specifies the condition to be evaluated after every HTTP API invocation. If the condition is evaluated as true, the task will be marked as completed. On the other hand, if the condition is evaluated as false, the conductor will schedule the next poll according to the configurations (pollingInterval & pollingStrategy). By default, this value is set to true. Note: While writing the terminal condition, It can be parameterized. In order to use the current http poll as input to the condition, a $ needs to be prefixed. For example, $.output.status
pollingInterval	Specify the time duration in seconds between each HTTP invocation.
pollingStrategy	It can take any of the following values: FIXED - The duration between each HTTP API invocation will be fixed. LINEAR_BACKOFF - The duration between each HTTP API invocation will be calculated by multiplying the poll count with pollingInterval. Note that the poll count is the incremental value based on each invocation. EXPONENTIAL_BACKOFF - The duration between each HTTP API invocation will be calculated by multiplying poll count with 2 base exponential of pollingInterval.

Apart from the above parameters, ensure that the following basic parameters for an HTTP task are also provided.

Attribute	Description
uri	Provide the Uniform Resource Identifier (URI) for the service. It can be partial when using vipAddress or else it indicates the server address.
method	Indicates the required action to be performed on the source. It can be GET, HEAD, POST, PUT, PATCH, DELETE, OPTIONS or TRACE.
accept	Provide the accept header as required by the server. By default, it is set to application/json.
contentType	Provide the content type for the server. The supported types are text/plain, text/html, and application/json. By default, it is set to application/json.
headers	Indicate a map of additional http headers to be sent along with the request.
body	Indicates the request body.
asyncComplete	If set, the task remains in the IN_PROGRESS state even after the execution. An external event (Task Update API or Event handler) is expected to mark the task as completed.
connectionTimeOut	Set the connection timeout in milliseconds. If set to 0, it is equivalent to infinity. By default, the value is set to 100.
readTimeOut	Set the read timeout in milliseconds. If set to 0, it is equivalent to infinity. By default, the value is set to 150.

Output Parameters

Attribute	Description
response	JSON body containing the response if present.
headers	Response Headers.
statusCode	HTTP Status Code.
reasonPhrase	HTTP Status Code's reason phrase.

Examples

UI

1. Add task type HTTP Poll.
2. Configure the Polling endpoint.
3. Configure the interval.

JSON Example

    {
      "name": "http_poll_task",
      "taskReferenceName": "http_poll_task_ref_1",
      "type": "HTTP_POLL",
      "inputParameters": {
        "http_request": {
          "uri": "https://orkes-api-tester.orkesconductor.com/api",
          "method": "POST",
          "connectionTimeOut": "3000",
          "readTimeOut": "3000",
          "accept": "application/json",
          "contentType": "application/json",
          "terminationCondition": "(function () {\n  return $.output.body.length > 10;\n})();",
          "pollingInterval": "60",
          "pollingStrategy": "FIXED",
          "body": "${workflow.input.payload}"
        }
      }
    }

Sample Workflow

Let’s see an example workflow:

    {
      "name": "your_workflow_name",
      "description": "Sample workflow to get started with HTTP POLL task.",
      "tasks": [
        {
          "name": "example",
          "taskReferenceName": "example",
          "inputParameters": {
            "http_request": {
              "uri": "https://jsonplaceholder.typicode.com/posts/1",
              "method": "GET",
              "terminationCondition": "$.output.body.length > 10 ? true : false;",
              "pollingInterval": "60",
              "pollingStrategy": "FIXED"
            }
          },
          "type": "HTTP_POLL"
        }
      ]
    }

So, here the input parameters for the HTTP_POLL task are defined as follows:

      "terminationCondition": "$.output.body.length > 10 ? true : false;",
      "pollingInterval": "60",
      "pollingStrategy": "FIXED"

The above configuration defines that the Conductor will invoke the HTTP API every 60 seconds until the jsonplaceholder gives the output that is longer than 10 characters.

note

Current invocation output can be referred to using $.output. Similarly, previous tasks' output can also be referred to using $.task_ref_name.output.