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<h1>Source code for certbot.error_handler</h1><div class="highlight"><pre>
<span></span><span class="sd">"""Registers functions to be called if an exception or signal occurs."""</span>
<span class="kn">import</span> <span class="nn">functools</span>
<span class="kn">import</span> <span class="nn">logging</span>
<span class="kn">import</span> <span class="nn">os</span>
<span class="kn">import</span> <span class="nn">signal</span>
<span class="kn">import</span> <span class="nn">traceback</span>
<span class="kn">from</span> <span class="nn">certbot</span> <span class="k">import</span> <span class="n">errors</span>
<span class="n">logger</span> <span class="o">=</span> <span class="n">logging</span><span class="o">.</span><span class="n">getLogger</span><span class="p">(</span><span class="n">__name__</span><span class="p">)</span>
<span class="c1"># _SIGNALS stores the signals that will be handled by the ErrorHandler. These</span>
<span class="c1"># signals were chosen as their default handler terminates the process and could</span>
<span class="c1"># potentially occur from inside Python. Signals such as SIGILL were not</span>
<span class="c1"># included as they could be a sign of something devious and we should terminate</span>
<span class="c1"># immediately.</span>
<span class="n">_SIGNALS</span> <span class="o">=</span> <span class="p">[</span><span class="n">signal</span><span class="o">.</span><span class="n">SIGTERM</span><span class="p">]</span>
<span class="k">if</span> <span class="n">os</span><span class="o">.</span><span class="n">name</span> <span class="o">!=</span> <span class="s2">"nt"</span><span class="p">:</span>
<span class="k">for</span> <span class="n">signal_code</span> <span class="ow">in</span> <span class="p">[</span><span class="n">signal</span><span class="o">.</span><span class="n">SIGHUP</span><span class="p">,</span> <span class="n">signal</span><span class="o">.</span><span class="n">SIGQUIT</span><span class="p">,</span>
<span class="n">signal</span><span class="o">.</span><span class="n">SIGXCPU</span><span class="p">,</span> <span class="n">signal</span><span class="o">.</span><span class="n">SIGXFSZ</span><span class="p">]:</span>
<span class="c1"># Adding only those signals that their default action is not Ignore.</span>
<span class="c1"># This is platform-dependent, so we check it dynamically.</span>
<span class="k">if</span> <span class="n">signal</span><span class="o">.</span><span class="n">getsignal</span><span class="p">(</span><span class="n">signal_code</span><span class="p">)</span> <span class="o">!=</span> <span class="n">signal</span><span class="o">.</span><span class="n">SIG_IGN</span><span class="p">:</span>
<span class="n">_SIGNALS</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">signal_code</span><span class="p">)</span>
<div class="viewcode-block" id="ErrorHandler"><a class="viewcode-back" href="../../api/error_handler.html#certbot.error_handler.ErrorHandler">[docs]</a><span class="k">class</span> <span class="nc">ErrorHandler</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
<span class="sd">"""Context manager for running code that must be cleaned up on failure.</span>
<span class="sd"> The context manager allows you to register functions that will be called</span>
<span class="sd"> when an exception (excluding SystemExit) or signal is encountered.</span>
<span class="sd"> Usage::</span>
<span class="sd"> handler = ErrorHandler(cleanup1_func, *cleanup1_args, **cleanup1_kwargs)</span>
<span class="sd"> handler.register(cleanup2_func, *cleanup2_args, **cleanup2_kwargs)</span>
<span class="sd"> with handler:</span>
<span class="sd"> do_something()</span>
<span class="sd"> Or for one cleanup function::</span>
<span class="sd"> with ErrorHandler(func, args, kwargs):</span>
<span class="sd"> do_something()</span>
<span class="sd"> If an exception is raised out of do_something, the cleanup functions will</span>
<span class="sd"> be called in last in first out order. Then the exception is raised.</span>
<span class="sd"> Similarly, if a signal is encountered, the cleanup functions are called</span>
<span class="sd"> followed by the previously received signal handler.</span>
<span class="sd"> Each registered cleanup function is called exactly once. If a registered</span>
<span class="sd"> function raises an exception, it is logged and the next function is called.</span>
<span class="sd"> Signals received while the registered functions are executing are</span>
<span class="sd"> deferred until they finish.</span>
<span class="sd"> """</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">func</span><span class="o">=</span><span class="kc">None</span><span class="p">,</span> <span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">body_executed</span> <span class="o">=</span> <span class="kc">False</span>
<span class="bp">self</span><span class="o">.</span><span class="n">funcs</span> <span class="o">=</span> <span class="p">[]</span>
<span class="bp">self</span><span class="o">.</span><span class="n">prev_handlers</span> <span class="o">=</span> <span class="p">{}</span>
<span class="bp">self</span><span class="o">.</span><span class="n">received_signals</span> <span class="o">=</span> <span class="p">[]</span>
<span class="k">if</span> <span class="n">func</span> <span class="ow">is</span> <span class="ow">not</span> <span class="kc">None</span><span class="p">:</span>
<span class="bp">self</span><span class="o">.</span><span class="n">register</span><span class="p">(</span><span class="n">func</span><span class="p">,</span> <span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">__enter__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">body_executed</span> <span class="o">=</span> <span class="kc">False</span>
<span class="bp">self</span><span class="o">.</span><span class="n">_set_signal_handlers</span><span class="p">()</span>
<span class="k">def</span> <span class="nf">__exit__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">exec_type</span><span class="p">,</span> <span class="n">exec_value</span><span class="p">,</span> <span class="n">trace</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">body_executed</span> <span class="o">=</span> <span class="kc">True</span>
<span class="n">retval</span> <span class="o">=</span> <span class="kc">False</span>
<span class="c1"># SystemExit is ignored to properly handle forks that don't exec</span>
<span class="k">if</span> <span class="n">exec_type</span> <span class="ow">in</span> <span class="p">(</span><span class="kc">None</span><span class="p">,</span> <span class="ne">SystemExit</span><span class="p">):</span>
<span class="k">return</span> <span class="n">retval</span>
<span class="k">elif</span> <span class="n">exec_type</span> <span class="ow">is</span> <span class="n">errors</span><span class="o">.</span><span class="n">SignalExit</span><span class="p">:</span>
<span class="n">logger</span><span class="o">.</span><span class="n">debug</span><span class="p">(</span><span class="s2">"Encountered signals: </span><span class="si">%s</span><span class="s2">"</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">received_signals</span><span class="p">)</span>
<span class="n">retval</span> <span class="o">=</span> <span class="kc">True</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">logger</span><span class="o">.</span><span class="n">debug</span><span class="p">(</span><span class="s2">"Encountered exception:</span><span class="se">\n</span><span class="si">%s</span><span class="s2">"</span><span class="p">,</span> <span class="s2">""</span><span class="o">.</span><span class="n">join</span><span class="p">(</span>
<span class="n">traceback</span><span class="o">.</span><span class="n">format_exception</span><span class="p">(</span><span class="n">exec_type</span><span class="p">,</span> <span class="n">exec_value</span><span class="p">,</span> <span class="n">trace</span><span class="p">)))</span>
<span class="bp">self</span><span class="o">.</span><span class="n">_call_registered</span><span class="p">()</span>
<span class="bp">self</span><span class="o">.</span><span class="n">_reset_signal_handlers</span><span class="p">()</span>
<span class="bp">self</span><span class="o">.</span><span class="n">_call_signals</span><span class="p">()</span>
<span class="k">return</span> <span class="n">retval</span>
<div class="viewcode-block" id="ErrorHandler.register"><a class="viewcode-back" href="../../api/error_handler.html#certbot.error_handler.ErrorHandler.register">[docs]</a> <span class="k">def</span> <span class="nf">register</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">func</span><span class="p">,</span> <span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">):</span>
<span class="sd">"""Sets func to be run with the given arguments during cleanup.</span>
<span class="sd"> :param function func: function to be called in case of an error</span>
<span class="sd"> """</span>
<span class="bp">self</span><span class="o">.</span><span class="n">funcs</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">functools</span><span class="o">.</span><span class="n">partial</span><span class="p">(</span><span class="n">func</span><span class="p">,</span> <span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">))</span></div>
<div class="viewcode-block" id="ErrorHandler._call_registered"><a class="viewcode-back" href="../../api/error_handler.html#certbot.error_handler.ErrorHandler._call_registered">[docs]</a> <span class="k">def</span> <span class="nf">_call_registered</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="sd">"""Calls all registered functions"""</span>
<span class="n">logger</span><span class="o">.</span><span class="n">debug</span><span class="p">(</span><span class="s2">"Calling registered functions"</span><span class="p">)</span>
<span class="k">while</span> <span class="bp">self</span><span class="o">.</span><span class="n">funcs</span><span class="p">:</span>
<span class="k">try</span><span class="p">:</span>
<span class="bp">self</span><span class="o">.</span><span class="n">funcs</span><span class="p">[</span><span class="o">-</span><span class="mi">1</span><span class="p">]()</span>
<span class="k">except</span> <span class="ne">Exception</span> <span class="k">as</span> <span class="n">error</span><span class="p">:</span> <span class="c1"># pylint: disable=broad-except</span>
<span class="n">logger</span><span class="o">.</span><span class="n">error</span><span class="p">(</span><span class="s2">"Encountered exception during recovery"</span><span class="p">)</span>
<span class="n">logger</span><span class="o">.</span><span class="n">exception</span><span class="p">(</span><span class="n">error</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">funcs</span><span class="o">.</span><span class="n">pop</span><span class="p">()</span></div>
<div class="viewcode-block" id="ErrorHandler._set_signal_handlers"><a class="viewcode-back" href="../../api/error_handler.html#certbot.error_handler.ErrorHandler._set_signal_handlers">[docs]</a> <span class="k">def</span> <span class="nf">_set_signal_handlers</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="sd">"""Sets signal handlers for signals in _SIGNALS."""</span>
<span class="k">for</span> <span class="n">signum</span> <span class="ow">in</span> <span class="n">_SIGNALS</span><span class="p">:</span>
<span class="n">prev_handler</span> <span class="o">=</span> <span class="n">signal</span><span class="o">.</span><span class="n">getsignal</span><span class="p">(</span><span class="n">signum</span><span class="p">)</span>
<span class="c1"># If prev_handler is None, the handler was set outside of Python</span>
<span class="k">if</span> <span class="n">prev_handler</span> <span class="ow">is</span> <span class="ow">not</span> <span class="kc">None</span><span class="p">:</span>
<span class="bp">self</span><span class="o">.</span><span class="n">prev_handlers</span><span class="p">[</span><span class="n">signum</span><span class="p">]</span> <span class="o">=</span> <span class="n">prev_handler</span>
<span class="n">signal</span><span class="o">.</span><span class="n">signal</span><span class="p">(</span><span class="n">signum</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">_signal_handler</span><span class="p">)</span></div>
<div class="viewcode-block" id="ErrorHandler._reset_signal_handlers"><a class="viewcode-back" href="../../api/error_handler.html#certbot.error_handler.ErrorHandler._reset_signal_handlers">[docs]</a> <span class="k">def</span> <span class="nf">_reset_signal_handlers</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="sd">"""Resets signal handlers for signals in _SIGNALS."""</span>
<span class="k">for</span> <span class="n">signum</span> <span class="ow">in</span> <span class="bp">self</span><span class="o">.</span><span class="n">prev_handlers</span><span class="p">:</span>
<span class="n">signal</span><span class="o">.</span><span class="n">signal</span><span class="p">(</span><span class="n">signum</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">prev_handlers</span><span class="p">[</span><span class="n">signum</span><span class="p">])</span>
<span class="bp">self</span><span class="o">.</span><span class="n">prev_handlers</span><span class="o">.</span><span class="n">clear</span><span class="p">()</span></div>
<div class="viewcode-block" id="ErrorHandler._signal_handler"><a class="viewcode-back" href="../../api/error_handler.html#certbot.error_handler.ErrorHandler._signal_handler">[docs]</a> <span class="k">def</span> <span class="nf">_signal_handler</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">signum</span><span class="p">,</span> <span class="n">unused_frame</span><span class="p">):</span>
<span class="sd">"""Replacement function for handling received signals.</span>
<span class="sd"> Store the received signal. If we are executing the code block in</span>
<span class="sd"> the body of the context manager, stop by raising signal exit.</span>
<span class="sd"> :param int signum: number of current signal</span>
<span class="sd"> """</span>
<span class="bp">self</span><span class="o">.</span><span class="n">received_signals</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">signum</span><span class="p">)</span>
<span class="k">if</span> <span class="ow">not</span> <span class="bp">self</span><span class="o">.</span><span class="n">body_executed</span><span class="p">:</span>
<span class="k">raise</span> <span class="n">errors</span><span class="o">.</span><span class="n">SignalExit</span></div>
<div class="viewcode-block" id="ErrorHandler._call_signals"><a class="viewcode-back" href="../../api/error_handler.html#certbot.error_handler.ErrorHandler._call_signals">[docs]</a> <span class="k">def</span> <span class="nf">_call_signals</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="sd">"""Finally call the deferred signals."""</span>
<span class="k">for</span> <span class="n">signum</span> <span class="ow">in</span> <span class="bp">self</span><span class="o">.</span><span class="n">received_signals</span><span class="p">:</span>
<span class="n">logger</span><span class="o">.</span><span class="n">debug</span><span class="p">(</span><span class="s2">"Calling signal </span><span class="si">%s</span><span class="s2">"</span><span class="p">,</span> <span class="n">signum</span><span class="p">)</span>
<span class="n">os</span><span class="o">.</span><span class="n">kill</span><span class="p">(</span><span class="n">os</span><span class="o">.</span><span class="n">getpid</span><span class="p">(),</span> <span class="n">signum</span><span class="p">)</span></div></div>
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