SLA misses and notifications in Apache Airflow - Step-by-Step Execution

Process Flow - SLA misses and notifications

DAG runs task

↓

Check if task finishes before SLA time

Yes↓

No action

↓

Send notification email

↓

Log SLA miss for review

The DAG runs a task and checks if it finishes before the SLA deadline. If it misses, an SLA miss event triggers a notification and logging.

Execution Sample

Apache Airflow

from airflow import DAG
from airflow.operators.bash import BashOperator
from airflow.utils.dates import days_ago
from datetime import timedelta

default_args = {
    'sla': timedelta(minutes=5),
    'email': ['[e-mail]'],
    'email_on_failure': True
}
with DAG('sla_example', default_args=default_args, start_date=days_ago(1)) as dag:
    task = BashOperator(task_id='task1', bash_command='sleep 600')

This DAG defines a task with a 5-minute SLA and email notification on SLA miss.

Process Table

Step	Task Status	Elapsed Time	SLA Time	SLA Miss?	Action Taken	Notification Sent
1	Task started	0s	5m	No	None	No
2	Task running	3m	5m	No	None	No
3	Task running	5m	5m	No	None	No
4	Task finished	10m	5m	Yes	SLA miss event triggered	Yes
5	Notification sent	-	-	-	Email sent to [e-mail]	Yes
6	SLA miss logged	-	-	-	Logged in Airflow UI	Yes
7	End	-	-	-	No further action	No

💡 Task finished after 10 minutes, exceeding SLA of 5 minutes, triggering SLA miss and notification.

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
task_status	Not started	Started	Running	Running	Finished	Finished
elapsed_time	0s	0s	3m	5m	10m	10m
sla_miss	False	False	False	False	True	True
notification_sent	False	False	False	False	True	True

Key Moments - 2 Insights

Why does the SLA miss only trigger after the task finishes, not during the run?

The SLA miss event triggers only after the task finishes and the elapsed time is compared to the SLA. See execution_table step 4 where the task finishes at 10 minutes, exceeding the 5-minute SLA.

Does Airflow send notifications automatically on SLA miss?

Yes, if email_on_failure or email_on_retry is set and email addresses are configured, Airflow sends notifications automatically on SLA miss events as shown in execution_table step 5.

Visual Quiz - 3 Questions

Look at the execution table, at which step does the SLA miss get detected?

A Step 3

B Step 4

C Step 2

D Step 5

💡 Hint

Check the 'SLA Miss?' column in the execution_table rows.

According to the variable tracker, what is the value of 'notification_sent' after step 3?

A True

B Undefined

C False

D Error

💡 Hint

Look at the 'notification_sent' row and the column 'After Step 3' in variable_tracker.

If the task finished in 4 minutes instead of 10, how would the SLA miss column change in the execution table?

A It would be 'No' at step 4

B It would be 'Yes' at step 4

C It would be 'Yes' at step 3

D It would be 'No' at step 2

💡 Hint

Compare elapsed time with SLA time in execution_table rows.

Concept Snapshot

SLA misses in Airflow occur when a task exceeds its defined SLA time.
Airflow detects SLA misses after task completion.
Notifications (e.g., emails) can be sent automatically on SLA miss.
Configure SLA and email in DAG default_args.
SLA miss events are logged for monitoring.

Full Transcript

This visual execution shows how Airflow handles SLA misses and notifications. The DAG runs a task with a 5-minute SLA. The task runs longer (10 minutes), so after it finishes, Airflow detects the SLA miss and triggers an event. This event sends an email notification and logs the miss in the Airflow UI. Variables like task status, elapsed time, SLA miss flag, and notification sent flag change step-by-step. Key moments clarify why SLA miss triggers after task completion and how notifications are sent. Quiz questions test understanding of when SLA miss is detected and notification status.