Trigger Flows When External Systems Change State

Trigger flows automatically by polling external systems for new data or events.

Polling triggers repeatedly check an external system at a fixed interval. When new data or events are detected, they automatically start a new flow execution.

Kestra provides polling triggers for a wide variety of systems, including databases, message queues, cloud storage, and FTP servers.

Polling triggers are not limited to external connectors. Some plugins also provide script-based polling triggers, allowing you to run code on an interval and emit only when a condition matches. The script plugins for Python, Shell, and JavaScript each provide ScriptTrigger and CommandsTrigger variants for polling with code or commands.

The polling frequency is controlled by the interval property. When triggered, the flow has access to the polling results through the trigger variable, making the retrieved data immediately available for downstream tasks.

Example

For example, the following flow polls a PostgreSQL table every 5 minutes. When new rows are available, it deletes them (to prevent duplicate processing) and logs the retrieved values.

id: jdbc-trigger
namespace: company.team

inputs:
  - id: db_url
    type: STRING

tasks:
  - id: update
    type: io.kestra.plugin.jdbc.postgresql.Query
    url: "{{ inputs.db_url }}"
    sql: DELETE FROM my_table

  - id: log
    type: io.kestra.plugin.core.log.Log
    message: "{{ trigger.rows }}"

triggers:
  - id: watch
    type: io.kestra.plugin.jdbc.postgresql.Trigger
    url: myurl
    interval: "PT5M"
    sql: "SELECT * FROM my_table"

Like all triggers, polling triggers support a when Pebble expression. When set, the trigger only creates an execution if when evaluates to true after new data is detected — useful for filtering results before the flow runs.

In Enterprise Edition, you can assign polling triggers to a specific Worker Queue using workerSelector.tags. This controls which workers execute the polling.

Browse the plugin catalog and filter by Trigger to see all available polling triggers, including file detection, database, and message queue variants.

Enterprise example

In Enterprise Edition, the Salesforce Trigger enables flows to start automatically when new records are created in Salesforce. For example, the flow below sends a Slack notification whenever a new contact is added.

id: salesforce_contact_trigger
namespace: company.sales
tasks:
  - id: notify_sales_manager
    type: io.kestra.plugin.slack.notifications.SlackIncomingWebhook
    url: "{{ secret('SLACK_WEBHOOK_URL') }}"
    messageText: "New contact created"

triggers:
  - id: new_contact_trigger
    type: io.kestra.plugin.ee.salesforce.Trigger
    interval: "PT5M"
    connection:
      username: "{{ secret('SALESFORCE_USERNAME') }}"
      password: "{{ secret('SALESFORCE_PASSWORD') }}"
      authEndpoint: "{{ secret('SALESFORCE_AUTH_ENDPOINT') }}"
    query: "SELECT Id, FirstName, LastName, Email, Phone, Company, CreatedDate FROM Contact WHERE CreatedDate >= LAST_N_MINUTES:5"