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add new monitoring blog post
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‎content/posts/170723-monitor-flask-apps.markdown‎

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@@ -33,6 +33,8 @@ the post:
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* [pyrollbar](https://rollbar.com/docs/notifier/pyrollbar/) monitoring
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instrumentation library,
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[version 0.13.12](https://github.com/rollbar/pyrollbar/tree/v0.13.12)
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* [blinker](https://pypi.python.org/pypi/blinker) for signaling support
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in Flask applications so pyrollbar can report on all errors
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* A [free Rollbar account](https://rollbar.com/) where we will send error
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data and view it when it is captured
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* [pip](https://pip.pypa.io/en/stable/) and the
@@ -43,7 +45,7 @@ the post:
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If you need help getting your
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[development environment](/development-environments.html) configured
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before running this code, take a look at
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[this guide for setting up Python 3 and Flask on Ubuntu 16.04 LTS](/blog/python-3-flask-green-unicorn-ubuntu-1604-xenial-xerus.html)
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[this guide for setting up Python 3 and Flask on Ubuntu 16.04 LTS](/blog/python-3-flask-green-unicorn-ubuntu-1604-xenial-xerus.html).
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All code in this blog post is available open source under the MIT license
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on GitHub under the
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Remember that you need to activate the virtualenv in every new terminal
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window where you want to use the virtualenv to run the project.
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Flask and Rollbar can now be installed into the now-activated virtualenv.
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Flask, Rollbar and Blinker can now be installed into the now-activated
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virtualenv.
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```
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pip install flask==0.12.2 rollbar==0.13.12
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pip install flask==0.12.2 rollbar==0.13.12 blinker==1.4
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```
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Our required dependencies should be installed within our virtualenv
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after a short installation period. Look for output like the following to
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confirm everything worked.
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```
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Installing collected packages: MarkupSafe, Jinja2, itsdangerous, click, Werkzeug, flask, idna, urllib3, chardet, certifi, requests, six, rollbar
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Running setup.py install for MarkupSafe ... done
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Installing collected packages: blinker, itsdangerous, click, MarkupSafe, Jinja2, Werkzeug, Flask, idna, urllib3, chardet, certifi, requests, six, rollbar
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Running setup.py install for blinker ... done
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Running setup.py install for itsdangerous ... done
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Running setup.py install for MarkupSafe ... done
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Running setup.py install for rollbar ... done
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Successfully installed Jinja2-2.9.6 MarkupSafe-1.0 Werkzeug-0.12.2 certifi-2017.4.17 chardet-3.0.4 click-6.7 flask-0.12.2 idna-2.5 itsdangerous-0.24 requests-2.18.1 rollbar-0.13.12 six-1.10.0 urllib3-1.21.1
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Successfully installed Flask-0.12.2 Jinja2-2.9.6 MarkupSafe-1.0 Werkzeug-0.12.2 blinker-1.4 certifi-2017.4.17 chardet-3.0.4 click-6.7 idna-2.5 itsdangerous-0.24 requests-2.18.1 rollbar-0.13.12 six-1.10.0 urllib3-1.21.1
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```
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Now that we have our Python dependencies installed into our virtualenv
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```python
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import re
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from flask import Flask, render_template
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from flask import Flask, render_template, Response
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from werkzeug.exceptions import NotFound
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app = Flask(__name__)
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MIN_PAGE_NAME_LENGTH = 2
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@app.route("/<string:page>/")
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def show_page(page):
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valid_length = len(page) >= MIN_PAGE_NAME_LENGTH
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valid_name = re.match('^[a-z]+$', page.lower()) is not None
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if valid_length and valid_name:
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return render_template("{}.html".format(page))
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else:
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msg = "Sorry, couldn't find page with name {}".format(page)
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raise NotFound(msg)
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try:
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valid_length = len(page) >= MIN_PAGE_NAME_LENGTH
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valid_name = re.match('^[a-z]+$', page.lower()) is not None
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if valid_length and valid_name:
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return render_template("{}.html".format(page))
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else:
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msg = "Sorry, couldn't find page with name {}".format(page)
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raise NotFound(msg)
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except:
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return Response("404 Not Found")
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if __name__ == "__main__":
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~~import os
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import re
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~~import rollbar
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from flask import Flask, render_template
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from flask import Flask, render_template, Response
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from werkzeug.exceptions import NotFound
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app = Flask(__name__)
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~~rollbar.init(os.environ.get('ROLLBAR_SECRET'))
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~~rollbar.report_message('Rollbar is configured correctly')
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MIN_PAGE_NAME_LENGTH = 2
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~~@app.before_first_request
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~~def add_monitoring():
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~~ rollbar.init(os.environ.get('ROLLBAR_SECRET'))
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~~ rollbar.report_message('Rollbar is configured correctly')
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@app.route("/<string:page>/")
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def show_page(page):
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valid_length = len(page) >= MIN_PAGE_NAME_LENGTH
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valid_name = re.match('^[a-z]+$', page.lower()) is not None
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if valid_length and valid_name:
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return render_template("{}.html".format(page))
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else:
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msg = "Sorry, couldn't find page with name {}".format(page)
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raise NotFound(msg)
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try:
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valid_length = len(page) >= MIN_PAGE_NAME_LENGTH
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valid_name = re.match('^[a-z]+$', page.lower()) is not None
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if valid_length and valid_name:
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return render_template("{}.html".format(page))
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else:
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msg = "Sorry, couldn't find page with name {}".format(page)
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raise NotFound(msg)
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except:
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return Response("404 Not Found")
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if __name__ == "__main__":
@@ -305,9 +317,66 @@ all the errors from our application, not a test event.
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## Testing Error Handling
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How do we make sure real errors are reported rather than just a simple
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test event? We just need to add a few more lines of code to our app.
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```python
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import os
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import re
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import rollbar
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~~import rollbar.contrib.flask
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from flask import Flask, render_template, Response
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~~from flask import got_request_exception
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from werkzeug.exceptions import NotFound
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app = Flask(__name__)
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MIN_PAGE_NAME_LENGTH = 2
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@app.before_first_request
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def add_monitoring():
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rollbar.init(os.environ.get('ROLLBAR_SECRET'))
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~~ ## delete the next line if you dont want this event anymore
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rollbar.report_message('Rollbar is configured correctly')
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~~ got_request_exception.connect(rollbar.contrib.flask.report_exception, app)
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@app.route("/<string:page>/")
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def show_page(page):
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try:
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valid_length = len(page) >= MIN_PAGE_NAME_LENGTH
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valid_name = re.match('^[a-z]+$', page.lower()) is not None
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if valid_length and valid_name:
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return render_template("{}.html".format(page))
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else:
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msg = "Sorry, couldn't find page with name {}".format(page)
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raise NotFound(msg)
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except:
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~~ rollbar.report_exc_info()
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return Response("404 Not Found")
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if __name__ == "__main__":
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app.run(debug=True)
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```
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The above highlighted code modifies the application so it reports all Flask
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errors as well as our HTTP 404 not found issues that happen within the
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`show_page` function.
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Make sure your Flask development server is running and try to go to
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[localhost:5000/b/](http://localhost:5000/b/). You will receive an HTTP
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404 exception and it will be reported to Rollbar. Next go to
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[localhost:5000/fullstackpython/](http://localhost:5000/fullstackpython/) and
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an HTTP 500 error will occur.
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You should see an aggregation of errors as you test out these errors:
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<img src="/img/170723-monitor-flask-apps/error-aggregation.jpg" width="100%" class="technical-diagram img-rounded" style="border:1px solid #ccc" alt="Rollbar dashboard showing aggregations of errors.">
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(links to Python docs)
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Woohoo, we finally have our Flask app reporting all errors that occur
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for any user back to the hosted Rollbar monitoring service!
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## What's Next?

‎static/img/170723-monitor-flask-apps/error-aggregation.jpg‎

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