Task status monitoring in Flask - Step-by-Step Execution

Concept Flow - Task status monitoring

Start Task

↓

Task Running

↓

Check Status Request

↓

Return Current Status

↓

Task Completed?

No→Wait for Next Check

Yes↓

Return Final Status

↓

End

This flow shows how a task starts, runs, and how status requests check and return the current state until completion.

Execution Sample

Flask

from flask import Flask, jsonify
app = Flask(__name__)
tasks = {}

@app.route('/start')
def start_task():
    tasks['task1'] = 'running'
    return jsonify({'status': 'started'})

This code starts a task and sets its status to 'running'.

Execution Table

Step	Action	Task Status Before	Task Status After	Response Sent
1	Start task1	{}	{'task1': 'running'}	{"status": "started"}
2	Check status of task1	{'task1': 'running'}	{'task1': 'running'}	{"task1": "running"}
3	Update task1 to completed	{'task1': 'running'}	{'task1': 'completed'}	None
4	Check status of task1	{'task1': 'completed'}	{'task1': 'completed'}	{"task1": "completed"}
5	No more status checks	{'task1': 'completed'}	{'task1': 'completed'}	End monitoring

💡 Task status is 'completed', so monitoring ends.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
tasks	{}	{'task1': 'running'}	{'task1': 'running'}	{'task1': 'completed'}	{'task1': 'completed'}	{'task1': 'completed'}

Key Moments - 2 Insights

Why does the task status not change when we only check it?

Checking the status (Step 2) only reads the current value without modifying it, so the status remains 'running' as shown in the execution_table row 2.

How do we know when to stop monitoring the task?

When the task status becomes 'completed' (Step 4), the monitoring ends as indicated in the exit_note and execution_table row 5.

Visual Quiz - 3 Questions

Look at the execution table, what is the task status after Step 1?

A {}

B 'completed'

C 'running'

D 'started'

💡 Hint

Check the 'Task Status After' column in row 1 of the execution_table.

At which step does the task status change to 'completed'?

A Step 3

B Step 2

C Step 4

D Step 5

💡 Hint

Look at the 'Task Status After' column to see when 'completed' first appears.

If we never update the task status to 'completed', what happens in the monitoring?

A Task status becomes 'failed'

B Monitoring continues indefinitely

C Monitoring ends immediately

D Task is removed from tasks dictionary

💡 Hint

Refer to the concept_flow where monitoring loops until status is 'completed'.

Concept Snapshot

Task status monitoring in Flask:
- Start task and set status (e.g., 'running')
- Provide endpoint to check current status
- Update status when task completes
- Continue checking until status is 'completed'
- Use a dictionary to track task states
- Return JSON responses with current status

Full Transcript

This example shows how to monitor a task's status in Flask. We start a task by setting its status to 'running' in a dictionary. When a client requests the status, the server returns the current state without changing it. Later, the task status is updated to 'completed'. The monitoring continues until the status is 'completed', at which point it stops. This process uses simple Flask routes and a dictionary to track task states, returning JSON responses to clients.