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<title>tipidee: the tipidee-config program</title>
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<p>
<a href="index.html">tipidee</a><br />
<a href="//skarnet.org/software/">Software</a><br />
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<h1> The <tt>tipidee-config</tt> program </h1>
<p>
<tt>tipidee-config</tt> is a tool that compiles a text configuration file
into a binary cdb file that is used by the <a href="tipideed.html">tipideed</a>
web server.
</p>
<h2> Interface </h2>
<pre>
tipidee-config [ -i <em>textfile</em> ] [ -o <em>cdbfile</em> ] [ -m <em>mode</em> ]
</pre>
<ul>
<li> tipidee-config reads the <a href="tipidee.conf.html">/etc/tipidee.conf</a>
configuration file, parses it, and outputs a cdb file to <tt>/etc/tipidee.conf.cdb</tt>.
(The <tt>/etc</tt> default can be changed at build time with the <tt>--sysconfdir</tt>
option to configure.) </li>
<li> It then exits 0. </li>
</ul>
<h2> Exit codes </h2>
<dl>
<dt> 0 </dt> <dd> success </dd>
<dt> 1 </dt> <dd> syntax error </dd>
<dt> 2 </dt> <dd> invalid inclusion (cycle or unauthorized duplicate) </dd>
<dt> 100 </dt> <dd> wrong usage </dd>
<dt> 111 </dt> <dd> system call failed </dd>
<dt> 129+ </dt> <dd> <a href="tipidee-config-preprocess.html">tipidee-config-preprocess</a> was killed </dd>
</dl>
<h2> Options </h2>
<dl>
<dt> -i <em>textfile</em> </dt>
<dd> Use <em>textfile</em> as input instead of <tt>/etc/tipidee.conf</tt> </dd>
<dt> -o <em>cdbfile</em> </dt>
<dd> Use <em>cdbfile</em> as output instead of <tt>/etc/tipidee.conf.cdb</tt>.
You can then use the <tt>-f <em>cdbfile</em> option to
<a href="tipideed.html">tipideed</>. </dd>
<dt> -m <em>mode</em> </dt>
<dd> Create the output file with permissions <em>mode</em> (given in octal).
Default is <strong>0644</strong>. Note that the output file should be readable
by the user <a href="tipideed.html">tipideed</a> is started as. If
<a href="tipideed.html">tipideed</a> is started as root and drops its privileges
itself, the file can be made private. </dd>
</dl>
<h2> Detailed operation </h2>
<ul>
<li> tipidee-config spawns a
<a href="tipidee-config-preprocess.html">tipidee-config-preprocess</a> helper
that reads <tt>/etc/tipidee.conf</tt>, takes care of all the inclusions, and
feeds it a single stream of data. If
<a href="tipidee-config-preprocess.html">tipidee-config-preprocess</a> dies
with a nonzero exit code at any point, tipidee-config exits with the same
error code, or 128 plus the signal number if
<a href="tipidee-config-preprocess.html">tipidee-config-preprocess</a> was
killed by a signal. </li>
<li> It reads the data and parses it, expecting it to follow the
<a href="tipidee.conf.html">/etc/tipidee.conf file format</a>. </li>
</li> On failure, it exits nonzero with an error message. </li>
<li> It supplies sane defaults for configuration values that have not
been provided. </li>
<li> It writes the data as a <a href="https://cr.yp.to/cdb/cdb.txt">cdb file</a>,
<tt>/etc/tipidee.conf.cdb</tt>. A previously existing file is replaced
atomically. </li>
<li> Running instances of <a href="tipideed.html">tipideed</a> will keep
using the old <tt>/etc/tipidee.conf.cdb</tt> data until their connection is closed;
new instances will use the new one. </li>
</ul>
<h2> Notes </h2>
<ul>
<li> It is by design that tipidee uses this unconventional "compile the
configuration file" approach. There are several benefits to it:
<ul>
<li> Parsing a configuration file is not very efficient. Every instance of
<a href="tipideed.html">tipideed</a> would have to do it on startup, and
there is an instance of <a href="tipideed.html">tipideed</a> for every
HTTP connection. Pre-parsing the configuration makes the initial server
response faster. </li>
<li> Data parsed by <a href="tipideed.html">tipideed</a> needs to use
<em>private dirty</em> memory for every instance, even if the data is
static — and that means incompressible RAM. By contrast, a cdb file
is mapped read-only, so its pages are <em>shared clean</em>, which means it's
essentially free. </li>
<li> <a href="tipideed.html">tipideed</a> is exposed to the network. You
want to its attack surface to be as small as possible. Taking the parsing code
out of it goes a long way — admittedly, having to parse HTTP in the
first place is more attack surface than a simple config file can ever hope
to be, but every little bit helps. </li>
<li> Run time is the worst time to detect errors. Nobody wants their
service to go down because Bob edited the live config file and made a typo.
Having the parsing done <em>offline</em> prevents that: tipidee-config
doubles as a syntax checker, and when it runs successfully, you know the
service will pick up the new config and be fine. </li>
<li> In general, decoupling the <em>live configuration</em>, which is
the one used by live services (here, <tt>/etc/tipidee.conf.cdb</tt>), from
the <em>working configuration</em>, which is the one that humans can
tinker with (here, <tt>/etc/tipidee.conf</tt>), is a good idea. Don't
touch production until you're ready to flip the switch atomically;
tipidee-config is the switch. </li>
</ul> </li>
</ul>
<p>
Just remember to run <tt>tipidee-config</tt> whenever you make
a modification to your config file. It not insurmountable.
</p>
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