Introduction

Errors and exceptions in Flask applications can be difficult to track, especially in production environments. Sentry provides real-time error tracking, performance monitoring, and debugging tools to help developers proactively detect and fix issues.

Why use Sentry in Flask?

✔ Automated error logging
✔ Detailed stack traces for debugging
✔ Performance insights
✔ Integration with Slack, GitHub, and other tools

This guide will walk you through setting up Sentry in a Flask application for error monitoring and performance optimization.

Setting Up Sentry in Flask

Install Sentry SDK

pip install sentry-sdk flask

Initialize Sentry in Flask

import sentry_sdk
from flask import Flask

sentry_sdk.init(
dsn="https://your-dsn-url@sentry.io/project-id",
traces_sample_rate=1.0,
integrations=[]
)

app = Flask(__name__)

@app.route("/")
def index():
return "Hello, Flask with Sentry!"

if __name__ == "__main__":
app.run(debug=True)

✅ Replaces manual error logging
✅ Captures all unhandled exceptions
✅ Supports distributed tracing

Capturing Exceptions Manually

Capture Handled Errors

from flask import jsonify

@app.route("/error")
def trigger_error():
try:
1 / 0  # Division by zero error
except ZeroDivisionError as e:
sentry_sdk.capture_exception(e)
return jsonify({"error": "Something went wrong!"}), 500

✅ Allows manual reporting of errors
✅ Provides full traceback in Sentry dashboard

Logging Custom Events

Sentry supports logging custom breadcrumbs and messages.

Capture Custom Messages

sentry_sdk.capture_message("This is a custom log message from Flask!")

Track User Context

sentry_sdk.set_user({"id": "123", "email": "user@example.com"})

✅ Helps track user-specific errors
✅ Improves debugging context

Performance Monitoring with Sentry

Enable Flask Performance Tracing

from sentry_sdk.integrations.flask import FlaskIntegration

sentry_sdk.init(
dsn="https://your-dsn-url@sentry.io/project-id",
integrations=[FlaskIntegration()],
traces_sample_rate=1.0  # Adjust sampling rate for performance monitoring
)

✅ Measures API response times
✅ Identifies slow database queries
✅ Provides distributed tracing across microservices

Filtering and Ignoring Errors

Ignore Specific Exceptions

sentry_sdk.init(
dsn="https://your-dsn-url@sentry.io/project-id",
ignore_errors=[KeyError, ValueError]
)

Sample Only Critical Errors

def before_send(event, hint):
if "exc_info" in hint:
exc_type, exc_value, _ = hint["exc_info"]
if isinstance(exc_value, KeyError):  
return None  # Ignore KeyError
return event

sentry_sdk.init(dsn="https://your-dsn-url@sentry.io/project-id", before_send=before_send)

✅ Prevents logging of non-critical errors
✅ Reduces noise in error tracking

Integrating Sentry with Slack and GitHub

Sentry allows sending alerts directly to Slack, GitHub Issues, Jira, or email.

Configure Slack Integration

  1. Go to Sentry Dashboard → Settings → Integrations.
  2. Select Slack and connect your workspace.
  3. Choose which projects to monitor.

Auto-Create GitHub Issues

Enable GitHub integration to auto-create issues from critical errors.

✅ Faster response to production errors
✅ Improved collaboration between teams

Conclusion

Integrating Sentry with Flask provides:

✔ Automated error tracking
✔ Performance insights
✔ Custom logging and filtering
✔ Seamless integration with Slack and GitHub

🚀 Set up Sentry in your Flask project today and start monitoring errors in real time!