SimpleHttpOperator for API calls in Apache Airflow - Step-by-Step Execution

Process Flow - SimpleHttpOperator for API calls

Start DAG

↓

SimpleHttpOperator triggers

↓

Send HTTP Request

↓

Receive HTTP Response

↓

Process Response (optional)

↓

Task Success or Failure

↓

End DAG

The SimpleHttpOperator starts when the DAG runs, sends an HTTP request, receives the response, optionally processes it, then marks the task success or failure.

Execution Sample

Apache Airflow

from airflow import DAG
from airflow.providers.http.operators.http import SimpleHttpOperator
from datetime import datetime

default_args = {'start_date': datetime(2024, 1, 1)}

dag = DAG('api_call_dag', default_args=default_args, schedule_interval='@daily')

api_task = SimpleHttpOperator(
    task_id='call_api',
    method='GET',
    http_conn_id='my_api',
    endpoint='data',
    dag=dag
)

This code defines a DAG with a SimpleHttpOperator task that sends a GET request to the 'data' endpoint using a connection named 'my_api'.

Process Table

Step	Action	HTTP Method	Endpoint	Request Sent	Response Status	Task State
1	DAG starts, SimpleHttpOperator triggers	GET	data	No	N/A	Pending
2	Send HTTP request	GET	data	Yes	N/A	Running
3	Receive HTTP response	GET	data	Yes	200 OK	Running
4	Process response (optional)	GET	data	Yes	200 OK	Running
5	Mark task success	GET	data	Yes	200 OK	Success

💡 Task completes successfully after receiving 200 OK response.

Status Tracker

Variable	Start	After Step 2	After Step 3	After Step 5
task_state	Pending	Running	Running	Success
http_response_status	None	None	200 OK	200 OK
request_sent	False	True	True	True

Key Moments - 2 Insights

Why does the task state change from Pending to Running before the HTTP request is sent?

The task state changes to Running as soon as the operator starts executing (Step 2 in execution_table), even before the HTTP request is actually sent.

What happens if the HTTP response status is not 200 OK?

If the response status is not 200 OK, the task may fail or retry depending on configuration, but in this trace (Step 3), 200 OK leads to success.

Visual Quiz - 3 Questions

Look at the execution table, what is the task state at Step 3?

A Pending

B Success

C Running

D Failed

💡 Hint

Check the 'Task State' column at Step 3 in the execution_table.

At which step is the HTTP request actually sent?

A Step 2

B Step 4

C Step 1

D Step 5

💡 Hint

Look at the 'Request Sent' column in execution_table to find when it changes to Yes.

If the response status was 404, how would the task state likely change at Step 5?

A Running

B Failed

C Success

D Pending

💡 Hint

Consider what happens when the HTTP response status is not 200 OK as explained in key_moments.

Concept Snapshot

SimpleHttpOperator sends HTTP requests in Airflow DAGs.
Define method, endpoint, and connection ID.
Task state moves: Pending -> Running -> Success/Failure.
Response status 200 means success.
Used for calling APIs during workflows.

Full Transcript

This visual execution trace shows how the SimpleHttpOperator works in Airflow. When the DAG starts, the operator triggers and changes the task state from Pending to Running. It sends an HTTP GET request to the specified endpoint using the configured connection. After sending the request, it waits for the HTTP response. Upon receiving a 200 OK response, the task processes the response if needed and then marks the task as Success. Variables like task_state and http_response_status update step-by-step. Key moments clarify why the task state changes early and what happens on non-200 responses. The quiz tests understanding of task states and request timing. This helps beginners see the exact flow of an API call task in Airflow.