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<div class="section" id="cluster-management">
<span id="id1"></span><h1>Cluster Management<a class="headerlink" href="#cluster-management" title="Permalink to this headline">¶</a></h1>
<p>py-postgresql provides cluster management tools in order to give the user
fine-grained control over a PostgreSQL cluster and access to information about an
installation of PostgreSQL.</p>
<div class="section" id="installations">
<span id="installation"></span><h2>Installations<a class="headerlink" href="#installations" title="Permalink to this headline">¶</a></h2>
<p><cite>postgresql.installation.Installation</cite> objects are primarily used to
access PostgreSQL installation information. Normally, they are created using a
dictionary constructed from the output of the <a class="reference external" href="http://www.postgresql.org/docs/current/static/app-pgconfig.html">pg_config</a> executable:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">postgresql.installation</span> <span class="kn">import</span> <span class="n">Installation</span><span class="p">,</span> <span class="n">pg_config_dictionary</span>
<span class="n">pg_install</span> <span class="o">=</span> <span class="n">Installation</span><span class="p">(</span><span class="n">pg_config_dictionary</span><span class="p">(</span><span class="s">'/usr/local/pgsql/bin/pg_config'</span><span class="p">))</span>
</pre></div>
</div>
<p>The extraction of <a class="reference external" href="http://www.postgresql.org/docs/current/static/app-pgconfig.html">pg_config</a> information is isolated from Installation
instantiation in order to allow Installations to be created from arbitrary
dictionaries. This can be useful in cases where the installation layout is
inconsistent with the standard PostgreSQL installation layout, or if a faux
Installation needs to be created for testing purposes.</p>
<div class="section" id="installation-interface-points">
<h3>Installation Interface Points<a class="headerlink" href="#installation-interface-points" title="Permalink to this headline">¶</a></h3>
<blockquote>
<div><dl class="docutils">
<dt><tt class="docutils literal"><span class="pre">Installation(info)</span></tt></dt>
<dd><p class="first">Instantiate an Installation using the given information. Normally, this
information is extracted from a <a class="reference external" href="http://www.postgresql.org/docs/current/static/app-pgconfig.html">pg_config</a> executable using
<cite>postgresql.installation.pg_config_dictionary</cite>:</p>
<div class="last highlight-python"><div class="highlight"><pre><span class="n">info</span> <span class="o">=</span> <span class="n">pg_config_dictionary</span><span class="p">(</span><span class="s">'/usr/local/pgsql/bin/pg_config'</span><span class="p">)</span>
<span class="n">pg_install</span> <span class="o">=</span> <span class="n">Installation</span><span class="p">(</span><span class="n">info</span><span class="p">)</span>
</pre></div>
</div>
</dd>
<dt><tt class="docutils literal"><span class="pre">Installation.version</span></tt></dt>
<dd><p class="first">The installation’s version string:</p>
<div class="last highlight-python"><div class="highlight"><pre><span class="n">pg_install</span><span class="o">.</span><span class="n">version</span>
<span class="s">'PostgreSQL 9.0devel'</span>
</pre></div>
</div>
</dd>
<dt><tt class="docutils literal"><span class="pre">Installation.version_info</span></tt></dt>
<dd><p class="first">A tuple containing the version’s <tt class="docutils literal"><span class="pre">(major,</span> <span class="pre">minor,</span> <span class="pre">patch,</span> <span class="pre">state,</span> <span class="pre">level)</span></tt>.
Where <tt class="docutils literal"><span class="pre">major</span></tt>, <tt class="docutils literal"><span class="pre">minor</span></tt>, <tt class="docutils literal"><span class="pre">patch</span></tt>, and <tt class="docutils literal"><span class="pre">level</span></tt> are <cite>int</cite> objects, and
<tt class="docutils literal"><span class="pre">state</span></tt> is a <cite>str</cite> object:</p>
<div class="last highlight-python"><div class="highlight"><pre><span class="n">pg_install</span><span class="o">.</span><span class="n">version_info</span>
<span class="p">(</span><span class="mi">9</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="s">'devel'</span><span class="p">,</span> <span class="mi">0</span><span class="p">)</span>
</pre></div>
</div>
</dd>
<dt><tt class="docutils literal"><span class="pre">Installation.ssl</span></tt></dt>
<dd>A <cite>bool</cite> indicating whether or not the installation has SSL support.</dd>
<dt><tt class="docutils literal"><span class="pre">Installation.configure_options</span></tt></dt>
<dd><p class="first">The options given to the <tt class="docutils literal"><span class="pre">configure</span></tt> script that built the installation. The
options are represented using a dictionary object whose keys are normalized
long option names, and whose values are the option’s argument. If the option
takes no argument, <cite>True</cite> will be used as the value.</p>
<p>The normalization of the long option names consists of removing the preceding
dashes, lowering the string, and replacing any dashes with underscores. For
instance, <tt class="docutils literal"><span class="pre">--enable-debug</span></tt> will be <tt class="docutils literal"><span class="pre">enable_debug</span></tt>:</p>
<div class="last highlight-python"><div class="highlight"><pre><span class="n">pg_install</span><span class="o">.</span><span class="n">configure_options</span>
<span class="p">{</span><span class="s">'enable_debug'</span><span class="p">:</span> <span class="bp">True</span><span class="p">,</span> <span class="s">'with_libxml'</span><span class="p">:</span> <span class="bp">True</span><span class="p">,</span>
<span class="s">'enable_cassert'</span><span class="p">:</span> <span class="bp">True</span><span class="p">,</span> <span class="s">'with_libedit_preferred'</span><span class="p">:</span> <span class="bp">True</span><span class="p">,</span>
<span class="s">'prefix'</span><span class="p">:</span> <span class="s">'/src/build/pg90'</span><span class="p">,</span> <span class="s">'with_openssl'</span><span class="p">:</span> <span class="bp">True</span><span class="p">,</span>
<span class="s">'enable_integer_datetimes'</span><span class="p">:</span> <span class="bp">True</span><span class="p">,</span> <span class="s">'enable_depend'</span><span class="p">:</span> <span class="bp">True</span><span class="p">}</span>
</pre></div>
</div>
</dd>
<dt><tt class="docutils literal"><span class="pre">Installation.paths</span></tt></dt>
<dd><p class="first">The paths of the installation as a dictionary where the keys are the path
identifiers and the values are the absolute file system paths. For instance,
<tt class="docutils literal"><span class="pre">'bindir'</span></tt> is associated with <tt class="docutils literal"><span class="pre">$PREFIX/bin</span></tt>, <tt class="docutils literal"><span class="pre">'libdir'</span></tt> is associated
with <tt class="docutils literal"><span class="pre">$PREFIX/lib</span></tt>, etc. The paths included in this dictionary are
listed on the class’ attributes: <cite>Installation.pg_directories</cite> and
<cite>Installation.pg_executables</cite>.</p>
<p>The keys that point to installation directories are: <tt class="docutils literal"><span class="pre">bindir</span></tt>, <tt class="docutils literal"><span class="pre">docdir</span></tt>,
<tt class="docutils literal"><span class="pre">includedir</span></tt>, <tt class="docutils literal"><span class="pre">pkgincludedir</span></tt>, <tt class="docutils literal"><span class="pre">includedir_server</span></tt>, <tt class="docutils literal"><span class="pre">libdir</span></tt>,
<tt class="docutils literal"><span class="pre">pkglibdir</span></tt>, <tt class="docutils literal"><span class="pre">localedir</span></tt>, <tt class="docutils literal"><span class="pre">mandir</span></tt>, <tt class="docutils literal"><span class="pre">sharedir</span></tt>, and <tt class="docutils literal"><span class="pre">sysconfdir</span></tt>.</p>
<p>The keys that point to installation executables are: <tt class="docutils literal"><span class="pre">pg_config</span></tt>, <tt class="docutils literal"><span class="pre">psql</span></tt>,
<tt class="docutils literal"><span class="pre">initdb</span></tt>, <tt class="docutils literal"><span class="pre">pg_resetxlog</span></tt>, <tt class="docutils literal"><span class="pre">pg_controldata</span></tt>, <tt class="docutils literal"><span class="pre">clusterdb</span></tt>, <tt class="docutils literal"><span class="pre">pg_ctl</span></tt>,
<tt class="docutils literal"><span class="pre">pg_dump</span></tt>, <tt class="docutils literal"><span class="pre">pg_dumpall</span></tt>, <tt class="docutils literal"><span class="pre">postgres</span></tt>, <tt class="docutils literal"><span class="pre">postmaster</span></tt>, <tt class="docutils literal"><span class="pre">reindexdb</span></tt>,
<tt class="docutils literal"><span class="pre">vacuumdb</span></tt>, <tt class="docutils literal"><span class="pre">ipcclean</span></tt>, <tt class="docutils literal"><span class="pre">createdb</span></tt>, <tt class="docutils literal"><span class="pre">ecpg</span></tt>, <tt class="docutils literal"><span class="pre">createuser</span></tt>,
<tt class="docutils literal"><span class="pre">createlang</span></tt>, <tt class="docutils literal"><span class="pre">droplang</span></tt>, <tt class="docutils literal"><span class="pre">dropuser</span></tt>, and <tt class="docutils literal"><span class="pre">pg_restore</span></tt>.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">If the executable does not exist, the value will be <cite>None</cite> instead
of an absoluate path.</p>
</div>
<p>To get the path to the <a class="reference external" href="http://www.postgresql.org/docs/current/static/app-psql.html">psql</a> executable:</p>
<div class="last highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">postgresql.installation</span> <span class="kn">import</span> <span class="n">Installation</span>
<span class="n">pg_install</span> <span class="o">=</span> <span class="n">Installation</span><span class="p">(</span><span class="s">'/usr/local/pgsql/bin/pg_config'</span><span class="p">)</span>
<span class="n">psql_path</span> <span class="o">=</span> <span class="n">pg_install</span><span class="o">.</span><span class="n">paths</span><span class="p">[</span><span class="s">'psql'</span><span class="p">]</span>
</pre></div>
</div>
</dd>
</dl>
</div></blockquote>
</div>
</div>
<div class="section" id="clusters">
<h2>Clusters<a class="headerlink" href="#clusters" title="Permalink to this headline">¶</a></h2>
<p><cite>postgresql.cluster.Cluster</cite> is the class used to manage a PostgreSQL
cluster–a data directory created by <a class="reference external" href="http://www.postgresql.org/docs/current/static/app-initdb.html">initdb</a>. A Cluster represents a data
directory with respect to a given installation of PostgreSQL, so
creating a <cite>postgresql.cluster.Cluster</cite> object requires a
<cite>postgresql.installation.Installation</cite>, and a
file system path to the data directory.</p>
<p>In part, a <cite>postgresql.cluster.Cluster</cite> is the Python programmer’s variant of
the <a class="reference external" href="http://www.postgresql.org/docs/current/static/app-pg-ctl.html">pg_ctl</a> command. However, it goes beyond the basic process control
functionality and extends into initialization and configuration as well.</p>
<p>A Cluster manages the server process using the <cite>subprocess</cite> module and
signals. The <cite>subprocess.Popen</cite> object, <tt class="docutils literal"><span class="pre">Cluster.daemon_process</span></tt>, is
retained when the Cluster starts the server process itself. This gives
the Cluster access to the result code of server process when it exits, and the
ability to redirect stderr and stdout to a parameterized file object using
subprocess features.</p>
<p>Despite its use of <cite>subprocess</cite>, Clusters can control a server process
that was <em>not</em> started by the Cluster’s <tt class="docutils literal"><span class="pre">start</span></tt> method.</p>
<div class="section" id="initializing-clusters">
<h3>Initializing Clusters<a class="headerlink" href="#initializing-clusters" title="Permalink to this headline">¶</a></h3>
<p><cite>postgresql.cluster.Cluster</cite> provides a method for initializing a
<cite>Cluster</cite>‘s data directory, <tt class="docutils literal"><span class="pre">init</span></tt>. This method provides a Python interface to
the PostgreSQL <a class="reference external" href="http://www.postgresql.org/docs/current/static/app-initdb.html">initdb</a> command.</p>
<p><tt class="docutils literal"><span class="pre">init</span></tt> is a regular method and accepts a few keyword parameters. Normally,
parameters are directly mapped to <a class="reference external" href="http://www.postgresql.org/docs/current/static/app-initdb.html">initdb</a> command options. However, <tt class="docutils literal"><span class="pre">password</span></tt>
makes use of initdb’s capability to read the superuser’s password from a file.
To do this, a temporary file is allocated internally by the method:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">postgresql.installation</span> <span class="kn">import</span> <span class="n">Installation</span><span class="p">,</span> <span class="n">pg_config_dictionary</span>
<span class="kn">from</span> <span class="nn">postgresql.cluster</span> <span class="kn">import</span> <span class="n">Cluster</span>
<span class="n">pg_install</span> <span class="o">=</span> <span class="n">Installation</span><span class="p">(</span><span class="n">pg_config_dictionary</span><span class="p">(</span><span class="s">'/usr/local/pgsql/bin/pg_config'</span><span class="p">))</span>
<span class="n">pg_cluster</span> <span class="o">=</span> <span class="n">Cluster</span><span class="p">(</span><span class="n">pg_install</span><span class="p">,</span> <span class="s">'pg_data'</span><span class="p">)</span>
<span class="n">pg_cluster</span><span class="o">.</span><span class="n">init</span><span class="p">(</span><span class="n">user</span> <span class="o">=</span> <span class="s">'pg'</span><span class="p">,</span> <span class="n">password</span> <span class="o">=</span> <span class="s">'secret'</span><span class="p">,</span> <span class="n">encoding</span> <span class="o">=</span> <span class="s">'utf-8'</span><span class="p">)</span>
</pre></div>
</div>
<p>The init method will block until the initdb command is complete. Once
initialized, the Cluster may be configured.</p>
</div>
<div class="section" id="configuring-clusters">
<h3>Configuring Clusters<a class="headerlink" href="#configuring-clusters" title="Permalink to this headline">¶</a></h3>
<p>A Cluster’s <a class="reference external" href="http://www.postgresql.org/docs/current/static/runtime-config.html">configuration file</a> can be manipulated using the
<cite>Cluster.settings</cite> mapping. The mapping’s methods will always access the
configuration file, so it may be desirable to cache repeat reads. Also, if
multiple settings are being applied, using the <tt class="docutils literal"><span class="pre">update()</span></tt> method may be
important to avoid writing the entire file multiple times:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">pg_cluster</span><span class="o">.</span><span class="n">settings</span><span class="o">.</span><span class="n">update</span><span class="p">({</span><span class="s">'listen_addresses'</span> <span class="p">:</span> <span class="s">'localhost'</span><span class="p">,</span> <span class="s">'port'</span> <span class="p">:</span> <span class="s">'6543'</span><span class="p">})</span>
</pre></div>
</div>
<p>Similarly, to avoid opening and reading the entire file multiple times,
<cite>Cluster.settings.getset</cite> should be used to retrieve multiple settings:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">d</span> <span class="o">=</span> <span class="n">pg_cluster</span><span class="o">.</span><span class="n">settings</span><span class="o">.</span><span class="n">getset</span><span class="p">(</span><span class="nb">set</span><span class="p">((</span><span class="s">'listen_addresses'</span><span class="p">,</span> <span class="s">'port'</span><span class="p">)))</span>
<span class="n">d</span>
<span class="p">{</span><span class="s">'listen_addresses'</span> <span class="p">:</span> <span class="s">'localhost'</span><span class="p">,</span> <span class="s">'port'</span> <span class="p">:</span> <span class="s">'6543'</span><span class="p">}</span>
</pre></div>
</div>
<p>Values contained in <tt class="docutils literal"><span class="pre">settings</span></tt> are always Python strings:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="k">assert</span> <span class="n">pg_cluster</span><span class="o">.</span><span class="n">settings</span><span class="p">[</span><span class="s">'max_connections'</span><span class="p">]</span><span class="o">.</span><span class="n">__class__</span> <span class="ow">is</span> <span class="nb">str</span>
</pre></div>
</div>
<p>The <tt class="docutils literal"><span class="pre">postgresql.conf</span></tt> file is only one part of the server configuration.
Structured access and manipulation of the <a class="reference external" href="http://www.postgresql.org/docs/current/static/auth-pg-hba-conf.html">pg_hba</a> file is not
supported. Clusters only provide the file path to the <a class="reference external" href="http://www.postgresql.org/docs/current/static/auth-pg-hba-conf.html">pg_hba</a> file:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">hba</span> <span class="o">=</span> <span class="nb">open</span><span class="p">(</span><span class="n">pg_cluster</span><span class="o">.</span><span class="n">hba_file</span><span class="p">)</span>
</pre></div>
</div>
<p>If the configuration of the Cluster is altered while the server process is
running, it may be necessary to signal the process that configuration changes
have been made. This signal can be sent using the <tt class="docutils literal"><span class="pre">Cluster.reload()</span></tt> method.
<tt class="docutils literal"><span class="pre">Cluster.reload()</span></tt> will send a SIGHUP signal to the server process. However,
not all changes to configuration settings can go into effect after calling
<tt class="docutils literal"><span class="pre">Cluster.reload()</span></tt>. In those cases, the server process will need to be
shutdown and started again.</p>
</div>
<div class="section" id="controlling-clusters">
<h3>Controlling Clusters<a class="headerlink" href="#controlling-clusters" title="Permalink to this headline">¶</a></h3>
<p>The server process of a Cluster object can be controlled with the <tt class="docutils literal"><span class="pre">start()</span></tt>,
<tt class="docutils literal"><span class="pre">stop()</span></tt>, <tt class="docutils literal"><span class="pre">shutdown()</span></tt>, <tt class="docutils literal"><span class="pre">kill()</span></tt>, and <tt class="docutils literal"><span class="pre">restart()</span></tt> methods.
These methods start the server process, signal the server process, or, in the
case of restart, a combination of the two.</p>
<p>When a Cluster starts the server process, it’s ran as a subprocess. Therefore,
if the current process exits, the server process will exit as well. <tt class="docutils literal"><span class="pre">start()</span></tt>
does <em>not</em> automatically daemonize the server process.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">Under Microsoft Windows, above does not hold true. The server process
will continue running despite the exit of the parent process.</p>
</div>
<p>To terminate a server process, one of these three methods should be called:
<tt class="docutils literal"><span class="pre">stop</span></tt>, <tt class="docutils literal"><span class="pre">shutdown</span></tt>, or <tt class="docutils literal"><span class="pre">kill</span></tt>. <tt class="docutils literal"><span class="pre">stop</span></tt> is a graceful shutdown and will
<em>wait for all clients to disconnect</em> before shutting down. <tt class="docutils literal"><span class="pre">shutdown</span></tt> will
close any open connections and safely shutdown the server process.
<tt class="docutils literal"><span class="pre">kill</span></tt> will immediately terminate the server process leading to recovery upon
starting the server process again.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">Using <tt class="docutils literal"><span class="pre">kill</span></tt> may cause shared memory to be leaked.</p>
</div>
<p>Normally, <cite>Cluster.shutdown</cite> is the appropriate way to terminate a server
process.</p>
</div>
<div class="section" id="cluster-interface-points">
<h3>Cluster Interface Points<a class="headerlink" href="#cluster-interface-points" title="Permalink to this headline">¶</a></h3>
<p>Methods and properties available on <cite>postgresql.cluster.Cluster</cite> instances:</p>
<blockquote>
<div><dl class="docutils">
<dt><tt class="docutils literal"><span class="pre">Cluster(installation,</span> <span class="pre">data_directory)</span></tt></dt>
<dd><p class="first">Create a <cite>postgresql.cluster.Cluster</cite> object for the specified
<cite>postgresql.installation.Installation</cite>, and <tt class="docutils literal"><span class="pre">data_directory</span></tt>.</p>
<p class="last">The <tt class="docutils literal"><span class="pre">data_directory</span></tt> must be an absoluate file system path. The directory
does <em>not</em> need to exist. The <tt class="docutils literal"><span class="pre">init()</span></tt> method may later be used to create
the cluster.</p>
</dd>
<dt><tt class="docutils literal"><span class="pre">Cluster.installation</span></tt></dt>
<dd>The Cluster’s <cite>postgresql.installation.Installation</cite> instance.</dd>
<dt><tt class="docutils literal"><span class="pre">Cluster.data_directory</span></tt></dt>
<dd>The absolute path to the PostgreSQL data directory.
This directory may not exist.</dd>
<dt><tt class="docutils literal"><span class="pre">Cluster.init([encoding</span> <span class="pre">=</span> <span class="pre">None[,</span> <span class="pre">user</span> <span class="pre">=</span> <span class="pre">None[,</span> <span class="pre">password</span> <span class="pre">=</span> <span class="pre">None]]])</span></tt></dt>
<dd><p class="first">Run the <a class="reference external" href="http://www.postgresql.org/docs/current/static/app-initdb.html">initdb</a> executable of the configured installation to initialize the
cluster at the configured data directory, <cite>Cluster.data_directory</cite>.</p>
<p><tt class="docutils literal"><span class="pre">encoding</span></tt> is mapped to <tt class="docutils literal"><span class="pre">-E</span></tt>, the default database encoding. By default,
the encoding is determined from the environment’s locale.</p>
<p><tt class="docutils literal"><span class="pre">user</span></tt> is mapped to <tt class="docutils literal"><span class="pre">-U</span></tt>, the database superuser name. By default, the
current user’s name.</p>
<p><tt class="docutils literal"><span class="pre">password</span></tt> is ultimately mapped to <tt class="docutils literal"><span class="pre">--pwfile</span></tt>. The argument given to the
long option is actually a path to the temporary file that holds the given
password.</p>
<p>Raises <cite>postgresql.cluster.InitDBError</cite> when <a class="reference external" href="http://www.postgresql.org/docs/current/static/app-initdb.html">initdb</a> returns a non-zero result
code.</p>
<p class="last">Raises <cite>postgresql.cluster.ClusterInitializationError</cite> when there is no
<a class="reference external" href="http://www.postgresql.org/docs/current/static/app-initdb.html">initdb</a> in the Installation.</p>
</dd>
<dt><tt class="docutils literal"><span class="pre">Cluster.initialized()</span></tt></dt>
<dd>Whether or not the data directory exists, <em>and</em> if it looks like a PostgreSQL
data directory. Meaning, the directory must contain a <tt class="docutils literal"><span class="pre">postgresql.conf</span></tt> file
and a <tt class="docutils literal"><span class="pre">base</span></tt> directory.</dd>
<dt><tt class="docutils literal"><span class="pre">Cluster.drop()</span></tt></dt>
<dd>Shutdown the Cluster’s server process and completely remove the
<cite>Cluster.data_directory</cite> from the file system.</dd>
<dt><tt class="docutils literal"><span class="pre">Cluster.pid()</span></tt></dt>
<dd>The server’s process identifier as a Python <cite>int</cite>. <cite>None</cite> if there is no
server process running.
This is a method rather than a property as it may read the PID from a file
in cases where the server process was not started by the Cluster.</dd>
<dt><tt class="docutils literal"><span class="pre">Cluster.start([logfile</span> <span class="pre">=</span> <span class="pre">None[,</span> <span class="pre">settings</span> <span class="pre">=</span> <span class="pre">None]])</span></tt></dt>
<dd><p class="first">Start the PostgreSQL server process for the Cluster if it is not
already running. This will execute <a class="reference external" href="http://www.postgresql.org/docs/current/static/app-postgres.html">postgres</a> as a subprocess.</p>
<p>If <tt class="docutils literal"><span class="pre">logfile</span></tt>, an opened and writable file object, is given, stderr and
stdout will be redirected to that file. By default, both stderr and stdout are
closed.</p>
<p class="last">If <tt class="docutils literal"><span class="pre">settings</span></tt> is given, the mapping or sequence of pairs will be used as
long options to the subprocess. For each item, <tt class="docutils literal"><span class="pre">--{key}={value}</span></tt> will be
given as an argument to the subprocess.</p>
</dd>
<dt><tt class="docutils literal"><span class="pre">Cluster.running()</span></tt></dt>
<dd>Whether or not the cluster’s server process is running. Returns <cite>True</cite> or
<cite>False</cite>. Even if <cite>True</cite> is returned, it does <em>not</em> mean that the server
process is ready to accept connections.</dd>
<dt><tt class="docutils literal"><span class="pre">Cluster.ready_for_connections()</span></tt></dt>
<dd><p class="first">Whether or not the Cluster is ready to accept connections. Usually called
after <cite>Cluster.start</cite>.</p>
<p class="last">Returns <cite>True</cite> when the Cluster can accept connections, <cite>False</cite> when it
cannot, and <cite>None</cite> if the Cluster’s server process is not running at all.</p>
</dd>
<dt><tt class="docutils literal"><span class="pre">Cluster.wait_until_started([timeout</span> <span class="pre">=</span> <span class="pre">10[,</span> <span class="pre">delay</span> <span class="pre">=</span> <span class="pre">0.05]])</span></tt></dt>
<dd><p class="first">Blocks the process until the cluster is identified as being ready for
connections. Usually called after <tt class="docutils literal"><span class="pre">Cluster.start()</span></tt>.</p>
<p>Raises <cite>postgresql.cluster.ClusterNotRunningError</cite> if the server process is
not running at all.</p>
<p>Raises <cite>postgresql.cluster.ClusterTimeoutError</cite> if
<cite>Cluster.ready_for_connections()</cite> does not return <cite>True</cite> within the given
<cite>timeout</cite> period.</p>
<p>Raises <cite>postgresql.cluster.ClusterStartupError</cite> if the server process
terminates while polling for readiness.</p>
<p class="last"><tt class="docutils literal"><span class="pre">timeout</span></tt> and <tt class="docutils literal"><span class="pre">delay</span></tt> are both in seconds. Where <tt class="docutils literal"><span class="pre">timeout</span></tt> is the
maximum time to wait for the Cluster to be ready for connections, and
<tt class="docutils literal"><span class="pre">delay</span></tt> is the time to sleep between calls to
<cite>Cluster.ready_for_connections()</cite>.</p>
</dd>
<dt><tt class="docutils literal"><span class="pre">Cluster.stop()</span></tt></dt>
<dd>Signal the cluster to shutdown when possible. The <em>server</em> will wait for all
clients to disconnect before shutting down.</dd>
<dt><tt class="docutils literal"><span class="pre">Cluster.shutdown()</span></tt></dt>
<dd>Signal the cluster to shutdown immediately. Any open client connections will
be closed.</dd>
<dt><tt class="docutils literal"><span class="pre">Cluster.kill()</span></tt></dt>
<dd>Signal the absolute destruction of the server process(SIGKILL).
<em>This will require recovery when the cluster is started again.</em>
<em>Shared memory may be leaked.</em></dd>
<dt><tt class="docutils literal"><span class="pre">Cluster.wait_until_stopped([timeout</span> <span class="pre">=</span> <span class="pre">10[,</span> <span class="pre">delay</span> <span class="pre">=</span> <span class="pre">0.05]])</span></tt></dt>
<dd><p class="first">Blocks the process until the cluster is identified as being shutdown. Usually
called after <cite>Cluster.stop</cite> or <cite>Cluster.shutdown</cite>.</p>
<p class="last">Raises <cite>postgresql.cluster.ClusterTimeoutError</cite> if
<cite>Cluster.ready_for_connections</cite> does not return <cite>None</cite> within the given
<cite>timeout</cite> period.</p>
</dd>
<dt><tt class="docutils literal"><span class="pre">Cluster.reload()</span></tt></dt>
<dd>Signal the server that it should reload its configuration files(SIGHUP).
Usually called after manipulating <cite>Cluster.settings</cite> or modifying the
contents of <cite>Cluster.hba_file</cite>.</dd>
<dt><tt class="docutils literal"><span class="pre">Cluster.restart([logfile</span> <span class="pre">=</span> <span class="pre">None[,</span> <span class="pre">settings</span> <span class="pre">=</span> <span class="pre">None[,</span> <span class="pre">timeout</span> <span class="pre">=</span> <span class="pre">10]]])</span></tt></dt>
<dd><p class="first">Stop the server process, wait until it is stopped, start the server
process, and wait until it has started.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">This calls <tt class="docutils literal"><span class="pre">Cluster.stop()</span></tt>, so it will wait until clients
disconnect before starting up again.</p>
</div>
<p class="last">The <tt class="docutils literal"><span class="pre">logfile</span></tt> and <tt class="docutils literal"><span class="pre">settings</span></tt> parameters will be given to <cite>Cluster.start</cite>.
<tt class="docutils literal"><span class="pre">timeout</span></tt> will be given to <cite>Cluster.wait_until_stopped</cite> and
<cite>Cluster.wait_until_started</cite>.</p>
</dd>
<dt><tt class="docutils literal"><span class="pre">Cluster.settings</span></tt></dt>
<dd><p class="first">A <cite>collections.Mapping</cite> interface to the <tt class="docutils literal"><span class="pre">postgresql.conf</span></tt> file of the
cluster.</p>
<p class="last">A notable extension to the mapping interface is the <tt class="docutils literal"><span class="pre">getset</span></tt> method. This
method will return a dictionary object containing the settings whose names
were contained in the <cite>set</cite> object given to the method.
This method should be used when multiple settings need to be retrieved from
the configuration file.</p>
</dd>
<dt><tt class="docutils literal"><span class="pre">Cluster.hba_file</span></tt></dt>
<dd>The path to the cluster’s <a class="reference external" href="http://www.postgresql.org/docs/current/static/auth-pg-hba-conf.html">pg_hba</a> file. This property respects the HBA file
location setting in <tt class="docutils literal"><span class="pre">postgresql.conf</span></tt>. Usually, <tt class="docutils literal"><span class="pre">$PGDATA/pg_hba.conf</span></tt>.</dd>
<dt><tt class="docutils literal"><span class="pre">Cluster.daemon_path</span></tt></dt>
<dd>The path to the executable to use to start the server process.</dd>
<dt><tt class="docutils literal"><span class="pre">Cluster.daemon_process</span></tt></dt>
<dd>The <cite>subprocess.Popen</cite> instance of the server process. <cite>None</cite> if the server
process was not started or was not started using the Cluster object.</dd>
</dl>
</div></blockquote>
</div>
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<h3><a href="index.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">Cluster Management</a><ul>
<li><a class="reference internal" href="#installations">Installations</a><ul>
<li><a class="reference internal" href="#installation-interface-points">Installation Interface Points</a></li>
</ul>
</li>
<li><a class="reference internal" href="#clusters">Clusters</a><ul>
<li><a class="reference internal" href="#initializing-clusters">Initializing Clusters</a></li>
<li><a class="reference internal" href="#configuring-clusters">Configuring Clusters</a></li>
<li><a class="reference internal" href="#controlling-clusters">Controlling Clusters</a></li>
<li><a class="reference internal" href="#cluster-interface-points">Cluster Interface Points</a></li>
</ul>
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