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diff --git a/app/static/doc/flask-docs/errorhandling.html b/app/static/doc/flask-docs/errorhandling.html new file mode 100644 index 0000000..9698707 --- /dev/null +++ b/app/static/doc/flask-docs/errorhandling.html @@ -0,0 +1,347 @@ + +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> + + +<html xmlns="http://www.w3.org/1999/xhtml"> + <head> + <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> + + <title>Handling Application Errors — Flask 0.8 documentation</title> + + <link rel="stylesheet" href="_static/flasky.css" type="text/css" /> + <link rel="stylesheet" href="_static/pygments.css" type="text/css" /> + + <script type="text/javascript"> + var DOCUMENTATION_OPTIONS = { + URL_ROOT: '', + VERSION: '0.8', + COLLAPSE_INDEX: false, + FILE_SUFFIX: '.html', + HAS_SOURCE: true + }; + </script> + <script type="text/javascript" src="_static/jquery.js"></script> + <script type="text/javascript" src="_static/underscore.js"></script> + <script type="text/javascript" src="_static/doctools.js"></script> + <link rel="top" title="Flask 0.8 documentation" href="index.html" /> + <link rel="next" title="Configuration Handling" href="config.html" /> + <link rel="prev" title="Testing Flask Applications" href="testing.html" /> + + + <link rel="apple-touch-icon" href="_static/touch-icon.png" /> + + <link media="only screen and (max-device-width: 480px)" href="_static/small_flask.css" type= "text/css" rel="stylesheet" /> + + </head> + <body> + <div class="related"> + <h3>Navigation</h3> + <ul> + <li class="right" style="margin-right: 10px"> + <a href="genindex.html" title="General Index" + accesskey="I">index</a></li> + <li class="right" > + <a href="config.html" title="Configuration Handling" + accesskey="N">next</a> |</li> + <li class="right" > + <a href="testing.html" title="Testing Flask Applications" + accesskey="P">previous</a> |</li> + <li><a href="index.html">Flask 0.8 documentation</a> »</li> + </ul> + </div> + + <div class="document"> + <div class="documentwrapper"> + <div class="bodywrapper"> + <div class="body"> + + <div class="section" id="handling-application-errors"> +<span id="application-errors"></span><h1>Handling Application Errors<a class="headerlink" href="#handling-application-errors" title="Permalink to this headline">¶</a></h1> +<p class="versionadded"> +<span class="versionmodified">New in version 0.3.</span></p> +<p>Applications fail, servers fail. Sooner or later you will see an exception +in production. Even if your code is 100% correct, you will still see +exceptions from time to time. Why? Because everything else involved will +fail. Here some situations where perfectly fine code can lead to server +errors:</p> +<ul class="simple"> +<li>the client terminated the request early and the application was still +reading from the incoming data.</li> +<li>the database server was overloaded and could not handle the query.</li> +<li>a filesystem is full</li> +<li>a harddrive crashed</li> +<li>a backend server overloaded</li> +<li>a programming error in a library you are using</li> +<li>network connection of the server to another system failed.</li> +</ul> +<p>And that’s just a small sample of issues you could be facing. So how do we +deal with that sort of problem? By default if your application runs in +production mode, Flask will display a very simple page for you and log the +exception to the <a class="reference internal" href="api.html#flask.Flask.logger" title="flask.Flask.logger"><tt class="xref py py-attr docutils literal"><span class="pre">logger</span></tt></a>.</p> +<p>But there is more you can do, and we will cover some better setups to deal +with errors.</p> +<div class="section" id="error-mails"> +<h2>Error Mails<a class="headerlink" href="#error-mails" title="Permalink to this headline">¶</a></h2> +<p>If the application runs in production mode (which it will do on your +server) you won’t see any log messages by default. Why is that? Flask +tries to be a zero-configuration framework. Where should it drop the logs +for you if there is no configuration? Guessing is not a good idea because +chances are, the place it guessed is not the place where the user has +permission to create a logfile. Also, for most small applications nobody +will look at the logs anyways.</p> +<p>In fact, I promise you right now that if you configure a logfile for the +application errors you will never look at it except for debugging an issue +when a user reported it for you. What you want instead is a mail the +second the exception happened. Then you get an alert and you can do +something about it.</p> +<p>Flask uses the Python builtin logging system, and it can actually send +you mails for errors which is probably what you want. Here is how you can +configure the Flask logger to send you mails for exceptions:</p> +<div class="highlight-python"><div class="highlight"><pre><span class="n">ADMINS</span> <span class="o">=</span> <span class="p">[</span><span class="s">'yourname@example.com'</span><span class="p">]</span> +<span class="k">if</span> <span class="ow">not</span> <span class="n">app</span><span class="o">.</span><span class="n">debug</span><span class="p">:</span> + <span class="kn">import</span> <span class="nn">logging</span> + <span class="kn">from</span> <span class="nn">logging.handlers</span> <span class="kn">import</span> <span class="n">SMTPHandler</span> + <span class="n">mail_handler</span> <span class="o">=</span> <span class="n">SMTPHandler</span><span class="p">(</span><span class="s">'127.0.0.1'</span><span class="p">,</span> + <span class="s">'server-error@example.com'</span><span class="p">,</span> + <span class="n">ADMINS</span><span class="p">,</span> <span class="s">'YourApplication Failed'</span><span class="p">)</span> + <span class="n">mail_handler</span><span class="o">.</span><span class="n">setLevel</span><span class="p">(</span><span class="n">logging</span><span class="o">.</span><span class="n">ERROR</span><span class="p">)</span> + <span class="n">app</span><span class="o">.</span><span class="n">logger</span><span class="o">.</span><span class="n">addHandler</span><span class="p">(</span><span class="n">mail_handler</span><span class="p">)</span> +</pre></div> +</div> +<p>So what just happened? We created a new +<a class="reference external" href="http://docs.python.org/dev/library/logging.handlers.html#logging.handlers.SMTPHandler" title="(in Python v3.3)"><tt class="xref py py-class docutils literal"><span class="pre">SMTPHandler</span></tt></a> that will send mails with the mail +server listening on <tt class="docutils literal"><span class="pre">127.0.0.1</span></tt> to all the <cite>ADMINS</cite> from the address +<em>server-error@example.com</em> with the subject “YourApplication Failed”. If +your mail server requires credentials, these can also be provided. For +that check out the documentation for the +<a class="reference external" href="http://docs.python.org/dev/library/logging.handlers.html#logging.handlers.SMTPHandler" title="(in Python v3.3)"><tt class="xref py py-class docutils literal"><span class="pre">SMTPHandler</span></tt></a>.</p> +<p>We also tell the handler to only send errors and more critical messages. +Because we certainly don’t want to get a mail for warnings or other +useless logs that might happen during request handling.</p> +<p>Before you run that in production, please also look at <a class="reference internal" href="#logformat"><em>Controlling the Log Format</em></a> to +put more information into that error mail. That will save you from a lot +of frustration.</p> +</div> +<div class="section" id="logging-to-a-file"> +<h2>Logging to a File<a class="headerlink" href="#logging-to-a-file" title="Permalink to this headline">¶</a></h2> +<p>Even if you get mails, you probably also want to log warnings. It’s a +good idea to keep as much information around that might be required to +debug a problem. Please note that Flask itself will not issue any +warnings in the core system, so it’s your responsibility to warn in the +code if something seems odd.</p> +<p>There are a couple of handlers provided by the logging system out of the +box but not all of them are useful for basic error logging. The most +interesting are probably the following:</p> +<ul class="simple"> +<li><a class="reference external" href="http://docs.python.org/dev/library/logging.handlers.html#logging.FileHandler" title="(in Python v3.3)"><tt class="xref py py-class docutils literal"><span class="pre">FileHandler</span></tt></a> - logs messages to a file on the +filesystem.</li> +<li><a class="reference external" href="http://docs.python.org/dev/library/logging.handlers.html#logging.handlers.RotatingFileHandler" title="(in Python v3.3)"><tt class="xref py py-class docutils literal"><span class="pre">RotatingFileHandler</span></tt></a> - logs messages to a file +on the filesystem and will rotate after a certain number of messages.</li> +<li><a class="reference external" href="http://docs.python.org/dev/library/logging.handlers.html#logging.handlers.NTEventLogHandler" title="(in Python v3.3)"><tt class="xref py py-class docutils literal"><span class="pre">NTEventLogHandler</span></tt></a> - will log to the system +event log of a Windows system. If you are deploying on a Windows box, +this is what you want to use.</li> +<li><a class="reference external" href="http://docs.python.org/dev/library/logging.handlers.html#logging.handlers.SysLogHandler" title="(in Python v3.3)"><tt class="xref py py-class docutils literal"><span class="pre">SysLogHandler</span></tt></a> - sends logs to a UNIX +syslog.</li> +</ul> +<p>Once you picked your log handler, do like you did with the SMTP handler +above, just make sure to use a lower setting (I would recommend +<cite>WARNING</cite>):</p> +<div class="highlight-python"><div class="highlight"><pre><span class="k">if</span> <span class="ow">not</span> <span class="n">app</span><span class="o">.</span><span class="n">debug</span><span class="p">:</span> + <span class="kn">import</span> <span class="nn">logging</span> + <span class="kn">from</span> <span class="nn">themodule</span> <span class="kn">import</span> <span class="n">TheHandlerYouWant</span> + <span class="n">file_handler</span> <span class="o">=</span> <span class="n">TheHandlerYouWant</span><span class="p">(</span><span class="o">...</span><span class="p">)</span> + <span class="n">file_handler</span><span class="o">.</span><span class="n">setLevel</span><span class="p">(</span><span class="n">logging</span><span class="o">.</span><span class="n">WARNING</span><span class="p">)</span> + <span class="n">app</span><span class="o">.</span><span class="n">logger</span><span class="o">.</span><span class="n">addHandler</span><span class="p">(</span><span class="n">file_handler</span><span class="p">)</span> +</pre></div> +</div> +</div> +<div class="section" id="controlling-the-log-format"> +<span id="logformat"></span><h2>Controlling the Log Format<a class="headerlink" href="#controlling-the-log-format" title="Permalink to this headline">¶</a></h2> +<p>By default a handler will only write the message string into a file or +send you that message as mail. A log record stores more information, +and it makes a lot of sense to configure your logger to also contain that +information so that you have a better idea of why that error happened, and +more importantly, where it did.</p> +<p>A formatter can be instantiated with a format string. Note that +tracebacks are appended to the log entry automatically. You don’t have to +do that in the log formatter format string.</p> +<p>Here some example setups:</p> +<div class="section" id="email"> +<h3>Email<a class="headerlink" href="#email" title="Permalink to this headline">¶</a></h3> +<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">logging</span> <span class="kn">import</span> <span class="n">Formatter</span> +<span class="n">mail_handler</span><span class="o">.</span><span class="n">setFormatter</span><span class="p">(</span><span class="n">Formatter</span><span class="p">(</span><span class="s">'''</span> +<span class="s">Message type: </span><span class="si">%(levelname)s</span><span class="s"></span> +<span class="s">Location: </span><span class="si">%(pathname)s</span><span class="s">:</span><span class="si">%(lineno)d</span><span class="s"></span> +<span class="s">Module: </span><span class="si">%(module)s</span><span class="s"></span> +<span class="s">Function: </span><span class="si">%(funcName)s</span><span class="s"></span> +<span class="s">Time: </span><span class="si">%(asctime)s</span><span class="s"></span> + +<span class="s">Message:</span> + +<span class="si">%(message)s</span><span class="s"></span> +<span class="s">'''</span><span class="p">))</span> +</pre></div> +</div> +</div> +<div class="section" id="file-logging"> +<h3>File logging<a class="headerlink" href="#file-logging" title="Permalink to this headline">¶</a></h3> +<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">logging</span> <span class="kn">import</span> <span class="n">Formatter</span> +<span class="n">file_handler</span><span class="o">.</span><span class="n">setFormatter</span><span class="p">(</span><span class="n">Formatter</span><span class="p">(</span> + <span class="s">'</span><span class="si">%(asctime)s</span><span class="s"> </span><span class="si">%(levelname)s</span><span class="s">: </span><span class="si">%(message)s</span><span class="s"> '</span> + <span class="s">'[in </span><span class="si">%(pathname)s</span><span class="s">:</span><span class="si">%(lineno)d</span><span class="s">]'</span> +<span class="p">))</span> +</pre></div> +</div> +</div> +<div class="section" id="complex-log-formatting"> +<h3>Complex Log Formatting<a class="headerlink" href="#complex-log-formatting" title="Permalink to this headline">¶</a></h3> +<p>Here is a list of useful formatting variables for the format string. Note +that this list is not complete, consult the official documentation of the +<a class="reference external" href="http://docs.python.org/dev/library/logging.html#logging" title="(in Python v3.3)"><tt class="xref py py-mod docutils literal"><span class="pre">logging</span></tt></a> package for a full list.</p> +<table border="1" class="docutils"> +<colgroup> +<col width="26%" /> +<col width="74%" /> +</colgroup> +<thead valign="bottom"> +<tr class="row-odd"><th class="head">Format</th> +<th class="head">Description</th> +</tr> +</thead> +<tbody valign="top"> +<tr class="row-even"><td><tt class="docutils literal"><span class="pre">%(levelname)s</span></tt></td> +<td>Text logging level for the message +(<tt class="docutils literal"><span class="pre">'DEBUG'</span></tt>, <tt class="docutils literal"><span class="pre">'INFO'</span></tt>, <tt class="docutils literal"><span class="pre">'WARNING'</span></tt>, +<tt class="docutils literal"><span class="pre">'ERROR'</span></tt>, <tt class="docutils literal"><span class="pre">'CRITICAL'</span></tt>).</td> +</tr> +<tr class="row-odd"><td><tt class="docutils literal"><span class="pre">%(pathname)s</span></tt></td> +<td>Full pathname of the source file where the +logging call was issued (if available).</td> +</tr> +<tr class="row-even"><td><tt class="docutils literal"><span class="pre">%(filename)s</span></tt></td> +<td>Filename portion of pathname.</td> +</tr> +<tr class="row-odd"><td><tt class="docutils literal"><span class="pre">%(module)s</span></tt></td> +<td>Module (name portion of filename).</td> +</tr> +<tr class="row-even"><td><tt class="docutils literal"><span class="pre">%(funcName)s</span></tt></td> +<td>Name of function containing the logging call.</td> +</tr> +<tr class="row-odd"><td><tt class="docutils literal"><span class="pre">%(lineno)d</span></tt></td> +<td>Source line number where the logging call was +issued (if available).</td> +</tr> +<tr class="row-even"><td><tt class="docutils literal"><span class="pre">%(asctime)s</span></tt></td> +<td>Human-readable time when the LogRecord` was +created. By default this is of the form +<tt class="docutils literal"><span class="pre">"2003-07-08</span> <span class="pre">16:49:45,896"</span></tt> (the numbers after +the comma are millisecond portion of the time). +This can be changed by subclassing the formatter +and overriding the +<a class="reference external" href="http://docs.python.org/dev/library/logging.html#logging.Formatter.formatTime" title="(in Python v3.3)"><tt class="xref py py-meth docutils literal"><span class="pre">formatTime()</span></tt></a> method.</td> +</tr> +<tr class="row-odd"><td><tt class="docutils literal"><span class="pre">%(message)s</span></tt></td> +<td>The logged message, computed as <tt class="docutils literal"><span class="pre">msg</span> <span class="pre">%</span> <span class="pre">args</span></tt></td> +</tr> +</tbody> +</table> +<p>If you want to further customize the formatting, you can subclass the +formatter. The formatter has three interesting methods:</p> +<dl class="docutils"> +<dt><a class="reference external" href="http://docs.python.org/dev/library/logging.html#logging.Formatter.format" title="(in Python v3.3)"><tt class="xref py py-meth docutils literal"><span class="pre">format()</span></tt></a>:</dt> +<dd>handles the actual formatting. It is passed a +<a class="reference external" href="http://docs.python.org/dev/library/logging.html#logging.LogRecord" title="(in Python v3.3)"><tt class="xref py py-class docutils literal"><span class="pre">LogRecord</span></tt></a> object and has to return the formatted +string.</dd> +<dt><a class="reference external" href="http://docs.python.org/dev/library/logging.html#logging.Formatter.formatTime" title="(in Python v3.3)"><tt class="xref py py-meth docutils literal"><span class="pre">formatTime()</span></tt></a>:</dt> +<dd>called for <cite>asctime</cite> formatting. If you want a different time format +you can override this method.</dd> +<dt><a class="reference external" href="http://docs.python.org/dev/library/logging.html#logging.Formatter.formatException" title="(in Python v3.3)"><tt class="xref py py-meth docutils literal"><span class="pre">formatException()</span></tt></a></dt> +<dd>called for exception formatting. It is passed an <tt class="xref py py-attr docutils literal"><span class="pre">exc_info</span></tt> +tuple and has to return a string. The default is usually fine, you +don’t have to override it.</dd> +</dl> +<p>For more information, head over to the official documentation.</p> +</div> +</div> +<div class="section" id="other-libraries"> +<h2>Other Libraries<a class="headerlink" href="#other-libraries" title="Permalink to this headline">¶</a></h2> +<p>So far we only configured the logger your application created itself. +Other libraries might log themselves as well. For example, SQLAlchemy uses +logging heavily in its core. While there is a method to configure all +loggers at once in the <a class="reference external" href="http://docs.python.org/dev/library/logging.html#logging" title="(in Python v3.3)"><tt class="xref py py-mod docutils literal"><span class="pre">logging</span></tt></a> package, I would not recommend using +it. There might be a situation in which you want to have multiple +separate applications running side by side in the same Python interpreter +and then it becomes impossible to have different logging setups for those.</p> +<p>Instead, I would recommend figuring out which loggers you are interested +in, getting the loggers with the <a class="reference external" href="http://docs.python.org/dev/library/logging.html#logging.getLogger" title="(in Python v3.3)"><tt class="xref py py-func docutils literal"><span class="pre">getLogger()</span></tt></a> function and +iterating over them to attach handlers:</p> +<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">logging</span> <span class="kn">import</span> <span class="n">getLogger</span> +<span class="n">loggers</span> <span class="o">=</span> <span class="p">[</span><span class="n">app</span><span class="o">.</span><span class="n">logger</span><span class="p">,</span> <span class="n">getLogger</span><span class="p">(</span><span class="s">'sqlalchemy'</span><span class="p">),</span> + <span class="n">getLogger</span><span class="p">(</span><span class="s">'otherlibrary'</span><span class="p">)]</span> +<span class="k">for</span> <span class="n">logger</span> <span class="ow">in</span> <span class="n">loggers</span><span class="p">:</span> + <span class="n">logger</span><span class="o">.</span><span class="n">addHandler</span><span class="p">(</span><span class="n">mail_handler</span><span class="p">)</span> + <span class="n">logger</span><span class="o">.</span><span class="n">addHandler</span><span class="p">(</span><span class="n">file_handler</span><span class="p">)</span> +</pre></div> +</div> +</div> +</div> + + + </div> + </div> + </div> + <div class="sphinxsidebar"> + <div class="sphinxsidebarwrapper"><p class="logo"><a href="index.html"> + <img class="logo" src="_static/flask.png" alt="Logo"/> +</a></p> + <h3><a href="index.html">Table Of Contents</a></h3> + <ul> +<li><a class="reference internal" href="#">Handling Application Errors</a><ul> +<li><a class="reference internal" href="#error-mails">Error Mails</a></li> +<li><a class="reference internal" href="#logging-to-a-file">Logging to a File</a></li> +<li><a class="reference internal" href="#controlling-the-log-format">Controlling the Log Format</a><ul> +<li><a class="reference internal" href="#email">Email</a></li> +<li><a class="reference internal" href="#file-logging">File logging</a></li> +<li><a class="reference internal" href="#complex-log-formatting">Complex Log Formatting</a></li> +</ul> +</li> +<li><a class="reference internal" href="#other-libraries">Other Libraries</a></li> +</ul> +</li> +</ul> +<h3>Related Topics</h3> +<ul> + <li><a href="index.html">Documentation overview</a><ul> + <li>Previous: <a href="testing.html" title="previous chapter">Testing Flask Applications</a></li> + <li>Next: <a href="config.html" title="next chapter">Configuration Handling</a></li> + </ul></li> +</ul> + <h3>This Page</h3> + <ul class="this-page-menu"> + <li><a href="_sources/errorhandling.txt" + rel="nofollow">Show Source</a></li> + </ul> +<div id="searchbox" style="display: none"> + <h3>Quick search</h3> + <form class="search" action="search.html" method="get"> + <input type="text" name="q" /> + <input type="submit" value="Go" /> + <input type="hidden" name="check_keywords" value="yes" /> + <input type="hidden" name="area" value="default" /> + </form> + <p class="searchtip" style="font-size: 90%"> + Enter search terms or a module, class or function name. + </p> +</div> +<script type="text/javascript">$('#searchbox').show(0);</script> + </div> + </div> + <div class="clearer"></div> + </div> + <div class="footer"> + © Copyright 2010, Armin Ronacher. + Created using <a href="http://sphinx.pocoo.org/">Sphinx</a>. + </div> + </body> +</html>
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