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<h1>Source code for certbot.lock</h1><div class="highlight"><pre>
<span></span><span class="sd">"""Implements file locks for locking files and directories in UNIX."""</span>
<span class="kn">import</span> <span class="nn">errno</span>
<span class="kn">import</span> <span class="nn">fcntl</span>
<span class="kn">import</span> <span class="nn">logging</span>
<span class="kn">import</span> <span class="nn">os</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="vm">__name__</span><span class="p">)</span>
<div class="viewcode-block" id="lock_dir"><a class="viewcode-back" href="../../api/lock.html#certbot.lock.lock_dir">[docs]</a><span class="k">def</span> <span class="nf">lock_dir</span><span class="p">(</span><span class="n">dir_path</span><span class="p">):</span>
<span class="sd">"""Place a lock file on the directory at dir_path.</span>
<span class="sd"> The lock file is placed in the root of dir_path with the name</span>
<span class="sd"> .certbot.lock.</span>
<span class="sd"> :param str dir_path: path to directory</span>
<span class="sd"> :returns: the locked LockFile object</span>
<span class="sd"> :rtype: LockFile</span>
<span class="sd"> :raises errors.LockError: if unable to acquire the lock</span>
<span class="sd"> """</span>
<span class="k">return</span> <span class="n">LockFile</span><span class="p">(</span><span class="n">os</span><span class="o">.</span><span class="n">path</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">dir_path</span><span class="p">,</span> <span class="s1">'.certbot.lock'</span><span class="p">))</span></div>
<div class="viewcode-block" id="LockFile"><a class="viewcode-back" href="../../api/lock.html#certbot.lock.LockFile">[docs]</a><span class="k">class</span> <span class="nc">LockFile</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
<span class="sd">"""A UNIX lock file.</span>
<span class="sd"> This lock file is released when the locked file is closed or the</span>
<span class="sd"> process exits. It cannot be used to provide synchronization between</span>
<span class="sd"> threads. It is based on the lock_file package by Martin Horcicka.</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">path</span><span class="p">):</span>
<span class="sd">"""Initialize and acquire the lock file.</span>
<span class="sd"> :param str path: path to the file to lock</span>
<span class="sd"> :raises errors.LockError: if unable to acquire the lock</span>
<span class="sd"> """</span>
<span class="nb">super</span><span class="p">(</span><span class="n">LockFile</span><span class="p">,</span> <span class="bp">self</span><span class="p">)</span><span class="o">.</span><span class="fm">__init__</span><span class="p">()</span>
<span class="bp">self</span><span class="o">.</span><span class="n">_path</span> <span class="o">=</span> <span class="n">path</span>
<span class="bp">self</span><span class="o">.</span><span class="n">_fd</span> <span class="o">=</span> <span class="kc">None</span>
<span class="bp">self</span><span class="o">.</span><span class="n">acquire</span><span class="p">()</span>
<div class="viewcode-block" id="LockFile.acquire"><a class="viewcode-back" href="../../api/lock.html#certbot.lock.LockFile.acquire">[docs]</a> <span class="k">def</span> <span class="nf">acquire</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="sd">"""Acquire the lock file.</span>
<span class="sd"> :raises errors.LockError: if lock is already held</span>
<span class="sd"> :raises OSError: if unable to open or stat the lock file</span>
<span class="sd"> """</span>
<span class="k">while</span> <span class="bp">self</span><span class="o">.</span><span class="n">_fd</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
<span class="c1"># Open the file</span>
<span class="n">fd</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">open</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">_path</span><span class="p">,</span> <span class="n">os</span><span class="o">.</span><span class="n">O_CREAT</span> <span class="o">|</span> <span class="n">os</span><span class="o">.</span><span class="n">O_WRONLY</span><span class="p">,</span> <span class="mo">0o600</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">_try_lock</span><span class="p">(</span><span class="n">fd</span><span class="p">)</span>
<span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">_lock_success</span><span class="p">(</span><span class="n">fd</span><span class="p">):</span>
<span class="bp">self</span><span class="o">.</span><span class="n">_fd</span> <span class="o">=</span> <span class="n">fd</span>
<span class="k">finally</span><span class="p">:</span>
<span class="c1"># Close the file if it is not the required one</span>
<span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">_fd</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
<span class="n">os</span><span class="o">.</span><span class="n">close</span><span class="p">(</span><span class="n">fd</span><span class="p">)</span></div>
<div class="viewcode-block" id="LockFile._try_lock"><a class="viewcode-back" href="../../api/lock.html#certbot.lock.LockFile._try_lock">[docs]</a> <span class="k">def</span> <span class="nf">_try_lock</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">fd</span><span class="p">):</span>
<span class="sd">"""Try to acquire the lock file without blocking.</span>
<span class="sd"> :param int fd: file descriptor of the opened file to lock</span>
<span class="sd"> """</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">fcntl</span><span class="o">.</span><span class="n">lockf</span><span class="p">(</span><span class="n">fd</span><span class="p">,</span> <span class="n">fcntl</span><span class="o">.</span><span class="n">LOCK_EX</span> <span class="o">|</span> <span class="n">fcntl</span><span class="o">.</span><span class="n">LOCK_NB</span><span class="p">)</span>
<span class="k">except</span> <span class="ne">IOError</span> <span class="k">as</span> <span class="n">err</span><span class="p">:</span>
<span class="k">if</span> <span class="n">err</span><span class="o">.</span><span class="n">errno</span> <span class="ow">in</span> <span class="p">(</span><span class="n">errno</span><span class="o">.</span><span class="n">EACCES</span><span class="p">,</span> <span class="n">errno</span><span class="o">.</span><span class="n">EAGAIN</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">"A lock on </span><span class="si">%s</span><span class="s2"> is held by another process."</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">_path</span><span class="p">)</span>
<span class="k">raise</span> <span class="n">errors</span><span class="o">.</span><span class="n">LockError</span><span class="p">(</span>
<span class="s2">"Another instance of Certbot is already running."</span><span class="p">)</span>
<span class="k">raise</span></div>
<div class="viewcode-block" id="LockFile._lock_success"><a class="viewcode-back" href="../../api/lock.html#certbot.lock.LockFile._lock_success">[docs]</a> <span class="k">def</span> <span class="nf">_lock_success</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">fd</span><span class="p">):</span>
<span class="sd">"""Did we successfully grab the lock?</span>
<span class="sd"> Because this class deletes the locked file when the lock is</span>
<span class="sd"> released, it is possible another process removed and recreated</span>
<span class="sd"> the file between us opening the file and acquiring the lock.</span>
<span class="sd"> :param int fd: file descriptor of the opened file to lock</span>
<span class="sd"> :returns: True if the lock was successfully acquired</span>
<span class="sd"> :rtype: bool</span>
<span class="sd"> """</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">stat1</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">stat</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">_path</span><span class="p">)</span>
<span class="k">except</span> <span class="ne">OSError</span> <span class="k">as</span> <span class="n">err</span><span class="p">:</span>
<span class="k">if</span> <span class="n">err</span><span class="o">.</span><span class="n">errno</span> <span class="o">==</span> <span class="n">errno</span><span class="o">.</span><span class="n">ENOENT</span><span class="p">:</span>
<span class="k">return</span> <span class="kc">False</span>
<span class="k">raise</span>
<span class="n">stat2</span> <span class="o">=</span> <span class="n">os</span><span class="o">.</span><span class="n">fstat</span><span class="p">(</span><span class="n">fd</span><span class="p">)</span>
<span class="c1"># If our locked file descriptor and the file on disk refer to</span>
<span class="c1"># the same device and inode, they're the same file.</span>
<span class="k">return</span> <span class="n">stat1</span><span class="o">.</span><span class="n">st_dev</span> <span class="o">==</span> <span class="n">stat2</span><span class="o">.</span><span class="n">st_dev</span> <span class="ow">and</span> <span class="n">stat1</span><span class="o">.</span><span class="n">st_ino</span> <span class="o">==</span> <span class="n">stat2</span><span class="o">.</span><span class="n">st_ino</span></div>
<span class="k">def</span> <span class="nf">__repr__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="n">repr_str</span> <span class="o">=</span> <span class="s1">'</span><span class="si">{0}</span><span class="s1">(</span><span class="si">{1}</span><span class="s1">) <'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="vm">__class__</span><span class="o">.</span><span class="vm">__name__</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">_path</span><span class="p">)</span>
<span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">_fd</span> <span class="ow">is</span> <span class="kc">None</span><span class="p">:</span>
<span class="n">repr_str</span> <span class="o">+=</span> <span class="s1">'released>'</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">repr_str</span> <span class="o">+=</span> <span class="s1">'acquired>'</span>
<span class="k">return</span> <span class="n">repr_str</span>
<div class="viewcode-block" id="LockFile.release"><a class="viewcode-back" href="../../api/lock.html#certbot.lock.LockFile.release">[docs]</a> <span class="k">def</span> <span class="nf">release</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="sd">"""Remove, close, and release the lock file."""</span>
<span class="c1"># It is important the lock file is removed before it's released,</span>
<span class="c1"># otherwise:</span>
<span class="c1">#</span>
<span class="c1"># process A: open lock file</span>
<span class="c1"># process B: release lock file</span>
<span class="c1"># process A: lock file</span>
<span class="c1"># process A: check device and inode</span>
<span class="c1"># process B: delete file</span>
<span class="c1"># process C: open and lock a different file at the same path</span>
<span class="c1">#</span>
<span class="c1"># Calling os.remove on a file that's in use doesn't work on</span>
<span class="c1"># Windows, but neither does locking with fcntl.</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">os</span><span class="o">.</span><span class="n">remove</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">_path</span><span class="p">)</span>
<span class="k">finally</span><span class="p">:</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">os</span><span class="o">.</span><span class="n">close</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">_fd</span><span class="p">)</span>
<span class="k">finally</span><span class="p">:</span>
<span class="bp">self</span><span class="o">.</span><span class="n">_fd</span> <span class="o">=</span> <span class="kc">None</span></div></div>
</pre></div>
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