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<!DOCTYPE html>
<html lang="en"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<meta charset="utf-8">
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<meta name="author" content="Matt Makai">
<meta name="description" content="Full Stack Python explains each layer of the web application stack, from the server up through the rendering in a user's browser.">
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<title>Logging - Full Stack Python</title>
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</div> <div class="row">
<div class="col-md-8">
<h1>Logging</h1>
<p>Logging saves output such as errors, warnings and event information to
files for debugging purposes. </p>
<h2>Why is logging important?</h2>
<p>Runtime exceptions that prevent code from running are important to log to
investigate and fix the source of the problems. Informational and debugging
logging also helps to understand how the application is performing even if
code is working as intended.</p>
<h2>Logging levels</h2>
<p>Logging is often grouped into several categories:</p>
<ol>
<li>Information</li>
<li>Debug</li>
<li>Warning</li>
<li>Error</li>
</ol>
<p>Logging errors that occur while a web framework is running is crucial to
understanding how your application is performing. </p>
<h2>Logging aggregators</h2>
<p>When you are running your application on several servers, it is helpful
to have a monitoring tool called a "logging aggregator". You can configure
your application to forward your system and application logs to one location
that provides tools for viewing, searching, and monitoring logging events
across your cluster. </p>
<p>Another advantage of log aggregatortion tools is they allow you to set up
custom alerts and alarms so you can get notified when error rates breach a
certain threshold.</p>
<h3>Open source log aggregators</h3>
<ul>
<li>
<p><a href="https://github.com/getsentry/sentry">Sentry</a> started as a Django-only
exception handling service but now has separate logging clients to cover
almost all major languages and frameworks. It still works really well for
Python-powered web applications and is often used in conjunction with other
monitoring tools. <a href="http://raven.readthedocs.org/en/latest/">Raven</a> is open
source Python client for Sentry.</p>
</li>
<li>
<p><a href="http://graylog2.org/">Graylog2</a> provides a central server for log
aggregation as well as a GUI for browsing and searching through log events.
There are libraries for most major languages, including python. Saves data
in Elasticache.</p>
</li>
<li>
<p><a href="http://logstash.net/">Logstash</a> Similar to Graylog2, logstash offers
features to programatically configure log data workflows.</p>
</li>
<li>
<p><a href="https://github.com/facebook/scribe">Scribe</a> A project written by Facebook
to aggregate logs. It's designed to run on multiple servers and scale with
the rest of your cluster. Uses the Thrift messaging format so it can be
used with any language. </p>
</li>
</ul>
<h3>Hosted logging services</h3>
<ul>
<li>
<p><a href="https://www.loggly.com/">Loggly</a> Loggly is a third party cloud based
application that aggregates logs. They have instructions for every major
language, including python. It includes email alerting on custom searches. </p>
</li>
<li>
<p><a href="https://papertrailapp.com/">Papertrail</a> Paper trail is similar to both
loggly and splunk and provides integration with S3 for long term storage.</p>
</li>
<li>
<p><a href="http://www.splunk.com/">Splunk</a> Splunk offers third party cloud and self
hosted solutions for event aggregation. It excells at searching and data
mining any text based data. </p>
</li>
<li>
<p><a href="http://raygun.io/">Raygun</a> logs errors and provides immediate notification
when issues arise.</p>
</li>
<li>
<p><a href="https://www.scalyr.com/">Scalyr</a> provides log aggregation, dashboards,
alerts and search in a user interface on top of standard logs.</p>
</li>
<li>
<p>There is a <a href="https://www.getsentry.com/welcome/">hosted version of Sentry</a>
in case you do not have the time to set up the open source project yourself.</p>
</li>
</ul>
<h2>Logging resources</h2>
<ul>
<li>
<p>This
<a href="http://www.blog.pythonlibrary.org/2012/08/02/python-101-an-intro-to-logging/">intro to logging</a>
presents the Python logging module and how to use it.</p>
</li>
<li>
<p><a href="http://www.hybridcluster.com/blog/logging-storytelling/">Logging as Storytelling</a>
is a multi-part series working the analogy that logs should read like
a story so you can better understand what's taking place in your web
application.
<a href="http://www.hybridcluster.com/blog/logging-storytelling-lets-add-action/">Part 2 describes actions</a>
and
<a href="http://www.hybridcluster.com/blog/logging-storytelling-3-types/">part 3 talks about types</a>.</p>
</li>
<li>
<p><a href="https://lukasa.co.uk/2014/05/A_Brief_Digression_About_Logging/">A Brief Digression About Logging</a>
is a short post that gets Python logging up and running quickly.</p>
</li>
<li>
<p><a href="https://hynek.me/articles/taking-some-pain-out-of-python-logging/">Taking the pain out of Python logging</a>
shows a logging set up with uWSGI.</p>
</li>
<li>
<p>Django's 1.3 release brought unified logging into project configurations.
This <a href="http://www.djm.org.uk/how-to-log-file-django-13-and-above/">post shows how to set up logging</a>
in a project's settings.py file. Caktus Group also has a nice tutorial on
<a href="http://www.caktusgroup.com/blog/2013/09/18/central-logging-django-graylog2-and-graypy/">central logging with graypy and Graylog2</a>.</p>
</li>
</ul>
<h2>Logging learning checklist</h2>
<p><i class="fa fa-check-square-o"></i>
Read how to integrate logging into your web application framework. </p>
<p><i class="fa fa-check-square-o"></i>
Ensure errors and anomalous results are logged. While these logs can be stored
in <a href="/monitoring.html">monitoring</a> solutions, it's best to have your own log
storage location to debug issues as they arise to complement other monitoring
systems.</p>
<p><i class="fa fa-check-square-o"></i>
Integrate logging for system events you may need to use for debugging purposes
later. For example, you may want to know the return values on functions when
they are above a certain threshold. </p>
<h3>Logging isn't enough. How do I analyze more data about the app?</h3>
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How can I monitor my live app with tools other than just logs?
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I want to learn more about the users of my application.
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<a href="/web-application-security.html" class="btn btn-success btn-full"><i class="fa fa-lock fa-inverse fa-2x"></i></a>
<p class="under-btn">
Something in the logs looks strange. How do I learn about security?
</p>
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<div class="panel-heading"><h3 class="panel-head">Logging</h3></div>
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<a href="/">Full Stack Python</a> is an open book that explains
each Python web application stack layer and provides the
best web resources for those topics.
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<h3 class="panel-head">Table of Contents</h3>
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<a href="/introduction.html" class="list-group-item smaller-item ">Introduction</a>
<a href="/web-frameworks.html" class="list-group-item smaller-item ">Web Frameworks</a>
<a href="/django.html" class="list-group-item smaller-item ">Django</a>
<a href="/flask.html" class="list-group-item smaller-item ">Flask</a>
<a href="/bottle.html" class="list-group-item smaller-item ">Bottle</a>
<a href="/morepath.html" class="list-group-item smaller-item ">Morepath</a>
<a href="/other-web-frameworks.html" class="list-group-item smaller-item ">Other Web Frameworks</a>
<a href="/deployment.html" class="list-group-item smaller-item ">Deployment</a>
<a href="/servers.html" class="list-group-item smaller-item ">Servers</a>
<a href="/platform-as-a-service.html" class="list-group-item smaller-item ">Platform-as-a-service</a>
<a href="/operating-systems.html" class="list-group-item smaller-item ">Operating Systems</a>
<a href="/web-servers.html" class="list-group-item smaller-item ">Web Servers</a>
<a href="/wsgi-servers.html" class="list-group-item smaller-item ">WSGI Servers</a>
<a href="/source-control.html" class="list-group-item smaller-item ">Source Control</a>
<a href="/application-dependencies.html" class="list-group-item smaller-item ">Application Dependencies</a>
<a href="/databases.html" class="list-group-item smaller-item ">Databases</a>
<a href="/no-sql-datastore.html" class="list-group-item smaller-item ">NoSQL Data Stores</a>
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