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authorgdamore <gdamore@users.noreply.github.com>2024-10-27 18:55:51 +0000
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+ <ol class="chapter"><li class="chapter-item expanded affix "><a href="../copyright.html">Copyright</a></li><li class="chapter-item expanded affix "><a href="../dedication.html">Dedication</a></li><li class="chapter-item expanded affix "><a href="../preface.html">Preface</a></li><li class="chapter-item expanded "><a href="../api/index.html"><strong aria-hidden="true">1.</strong> API Reference</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../api/msg.html"><strong aria-hidden="true">1.1.</strong> Messages</a></li><li class="chapter-item expanded "><a href="../api/memory.html"><strong aria-hidden="true">1.2.</strong> Memory</a></li><li class="chapter-item expanded "><a href="../api/time.html"><strong aria-hidden="true">1.3.</strong> Time</a></li><li class="chapter-item expanded "><a href="../api/url.html"><strong aria-hidden="true">1.4.</strong> URLs</a></li><li class="chapter-item expanded "><a href="../api/aio.html"><strong aria-hidden="true">1.5.</strong> Asynchronous I/O</a></li><li class="chapter-item expanded "><a href="../api/synch.html"><strong aria-hidden="true">1.6.</strong> Synchronization</a></li><li class="chapter-item expanded "><a href="../api/thread.html"><strong aria-hidden="true">1.7.</strong> Threads</a></li><li class="chapter-item expanded "><a href="../api/logging.html"><strong aria-hidden="true">1.8.</strong> Logging</a></li><li class="chapter-item expanded "><a href="../api/stats.html" class="active"><strong aria-hidden="true">1.9.</strong> Statistics</a></li><li class="chapter-item expanded "><a href="../api/errors.html"><strong aria-hidden="true">1.10.</strong> Errors</a></li><li class="chapter-item expanded "><a href="../api/misc.html"><strong aria-hidden="true">1.11.</strong> Miscellaneous</a></li><li class="chapter-item expanded "><a href="../api/id_map.html"><strong aria-hidden="true">1.12.</strong> ID Map</a></li><li class="chapter-item expanded "><a href="../api/cmd_opts.html"><strong aria-hidden="true">1.13.</strong> Command Options</a></li></ol></li><li class="chapter-item expanded "><a href="../proto/index.html"><strong aria-hidden="true">2.</strong> Protocols</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../proto/bus.html"><strong aria-hidden="true">2.1.</strong> BUS Protocol</a></li><li class="chapter-item expanded "><a href="../proto/pair.html"><strong aria-hidden="true">2.2.</strong> PAIR Protocol</a></li><li class="chapter-item expanded "><a href="../proto/pub.html"><strong aria-hidden="true">2.3.</strong> PUB Protocol</a></li><li class="chapter-item expanded "><a href="../proto/pull.html"><strong aria-hidden="true">2.4.</strong> PULL Protocol</a></li><li class="chapter-item expanded "><a href="../proto/push.html"><strong aria-hidden="true">2.5.</strong> PUSH Protocol</a></li><li class="chapter-item expanded "><a href="../proto/rep.html"><strong aria-hidden="true">2.6.</strong> REP Protocol</a></li><li class="chapter-item expanded "><a href="../proto/req.html"><strong aria-hidden="true">2.7.</strong> REQ Protocol</a></li><li class="chapter-item expanded "><a href="../proto/respondent.html"><strong aria-hidden="true">2.8.</strong> RESPONDENT Protocol</a></li><li class="chapter-item expanded "><a href="../proto/sub.html"><strong aria-hidden="true">2.9.</strong> SUB Protocol</a></li><li class="chapter-item expanded "><a href="../proto/surveyor.html"><strong aria-hidden="true">2.10.</strong> SURVEYOR Protocol</a></li></ol></li><li class="chapter-item expanded "><a href="../tran/index.html"><strong aria-hidden="true">3.</strong> Transports</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../tran/inproc.html"><strong aria-hidden="true">3.1.</strong> Intra-Process Transport</a></li><li class="chapter-item expanded "><a href="../tran/ipc.html"><strong aria-hidden="true">3.2.</strong> Inter-Process Transport</a></li><li class="chapter-item expanded "><a href="../tran/socket.html"><strong aria-hidden="true">3.3.</strong> BSD Socket (Experimental)</a></li><li class="chapter-item expanded "><a href="../tran/udp.html"><strong aria-hidden="true">3.4.</strong> UDP Transport (Experimental)</a></li></ol></li><li class="chapter-item expanded "><a href="../migrate/index.html"><strong aria-hidden="true">4.</strong> Migration Guides</a><a class="toggle"><div>❱</div></a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../migrate/nng1.html"><strong aria-hidden="true">4.1.</strong> Migrating from NNG 1.x</a></li><li class="chapter-item expanded "><a href="../migrate/nanomsg.html"><strong aria-hidden="true">4.2.</strong> Migrating from libnanomsg</a></li></ol></li><li class="chapter-item expanded "><a href="../indexing.html">Index</a></li></ol>
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+
+</style>
+<h1 id="statistics"><a class="header" href="#statistics">Statistics</a></h1>
+<p>To facilitate debugging and support situations, the <em>NNG</em> library
+provides for collection and reporting of numerous <a name="a001"></a>statistics.</p>
+<p>These statistics are organized in a tree, and include both values,
+and metadata describing the statistics. In order to be efficient and
+minimize the impact of maintaining statistics, an explicit snapshot
+of statistics must be taken, and that snapshot can then be processed.</p>
+<div class="mdbook-alerts mdbook-alerts-note">
+<p class="mdbook-alerts-title">
+ <span class="mdbook-alerts-icon"></span>
+ note
+</p>
+<p>Statistics may be disabled by build-time configuration options,
+in order to reduce program size and run-time overheads.</p>
+</div>
+<h2 id="statistic-structure"><a class="header" href="#statistic-structure">Statistic Structure</a></h2>
+<pre><code class="language-c">typedef struct nng_stat nng_stat;
+</code></pre>
+<p>The <a name="a002"></a><code>nng_stat</code> structure represents a statistic, which is a single value
+collected at a specific point in time.</p>
+<p>This structure has meta-data describing the value, the value itself, and links
+to any sibling or child statistics.</p>
+<div class="mdbook-alerts mdbook-alerts-note">
+<p class="mdbook-alerts-title">
+ <span class="mdbook-alerts-icon"></span>
+ note
+</p>
+<p>The presence, name, and semantics of any given statistic are
+subject to change at any time and without notice.</p>
+</div>
+<h2 id="collecting-a-snapshot"><a class="header" href="#collecting-a-snapshot">Collecting a Snapshot</a></h2>
+<pre><code class="language-c">int nng_stats_get(nng_stat **statsp);
+</code></pre>
+<p>The <a name="a003"></a><code>nng_stats_get</code> function takes a snapshot of the statistics for
+the system and returns it through the pointer <em>statsp</em>.
+This function may return <a href="/api/errors.html#NNG_ENOMEM"><code>NNG_ENOMEM</code></a> if memory is exhausted, or <a href="/api/errors.html#NNG_ENOTSUP"><code>NNG_ENOTSUP</code></a> if the statistics
+support is not enabled in the build, but is otherwise expected to return zero.</p>
+<h2 id="freeing-a-snapshot"><a class="header" href="#freeing-a-snapshot">Freeing a Snapshot</a></h2>
+<pre><code class="language-c">void nng_stats_free(nng_stat *stat);
+</code></pre>
+<p>The <a name="a004"></a><code>nng_stats_free</code> function deallocates the snapshot referenced by <em>stat</em>.</p>
+<div class="mdbook-alerts mdbook-alerts-important">
+<p class="mdbook-alerts-title">
+ <span class="mdbook-alerts-icon"></span>
+ important
+</p>
+<p>The <em>stat</em> must be root of the statistics tree, i.e. the value that was returned
+through <em>statsp</em> using the function <code>nng_stats_get</code>.</p>
+</div>
+<h2 id="traversing-the-tree"><a class="header" href="#traversing-the-tree">Traversing the Tree</a></h2>
+<pre><code class="language-c">const nng_stat *nng_stat_child(const nng_stat *stat);
+const nng_stat *nng_stat_next(const nng_stat *stat);
+</code></pre>
+<p>Traversing the tree of statistics is done using the <a name="a005"></a><code>nng_stat_child</code> and
+<a name="a006"></a><code>nng_stat_next</code> functions.</p>
+<p>The <code>nng_stat_child</code> function returns either the first child of <em>stat</em>,
+or <code>NULL</code> if the <em>stat</em> has no children.</p>
+<p>The <code>nng_stat_next</code> function returns the nearest sibling to the right of <em>stat</em>,
+or <code>NULL</code> if <em>stat</em> has no more siblings to the right.</p>
+<h2 id="finding-a-statistic"><a class="header" href="#finding-a-statistic">Finding a Statistic</a></h2>
+<pre><code class="language-c">const nng_stat *nng_stat_find(const nng_stat *stat, const char *name);
+const nng_stat *nng_stat_find_dialer(const nng_stat *stat, nng_dialer dialer);
+const nng_stat *nng_stat_find_listener(const nng_stat *stat, nng_dialer listener);
+const nng_stat *nng_stat_find_socket(const nng_stat *stat, nng_dialer socket);
+</code></pre>
+<p>Sometimes it is easiest to search for a specific statistic, matching by name,
+or possibly to find the tree of statistics associated iwth a specific <a href="/TODO.html">socket</a>,
+<a href="/TODO.html">dialer</a>, or <a href="/TODO.html">listener</a>.</p>
+<p>The <code>nng_stat_find</code> functions are provided for this purpose.</p>
+<p>The <a name="a007"></a><code>nng_stat_find</code> function returns the first statistic within the subtree of
+statistics <em>stat</em>, with the given <em>name</em>. If no such statistic can be found, <code>NULL</code>
+is returned.</p>
+<p>The <a name="a008"></a><code>nng_stat_find_dialer</code>, <a name="a009"></a><code>nng_stat_find_listener</code>, and <a name="a010"></a><code>nng_stat_find_socket</code>
+return the statistics subtree for the given dialer, listener, or socket object. If no such
+statistic can be found, then they return <code>NULL</code>.
+These functions should be provided the root of the statistic tree, in order to ensure
+that they can find the desired object.</p>
+<h2 id="statistic-identification"><a class="header" href="#statistic-identification">Statistic Identification</a></h2>
+<pre><code class="language-c">const char *nng_stat_name(const nng_stat *stat);
+const char *nng_stat_desc(const nng_stat *stat);
+</code></pre>
+<p>Every statistic has a name, returned by <a name="a011"></a><code>nng_stat_name</code>, and a description, returned by
+<a name="a012"></a><code>nng_stat_desc</code>. Descriptions are human-readable text, which might be useful for display.</p>
+<h2 id="statistic-type"><a class="header" href="#statistic-type">Statistic Type</a></h2>
+<pre><code class="language-c">int nng_stat_type(const nng_stat *stat);
+</code></pre>
+<p>The function <a name="a013"></a><code>nng_stat_type</code> returns the type of the statistic.
+The type of a statistic determines the nature of the value, and which
+function can be used to obtain that value.</p>
+<ul>
+<li>
+<p><a name="a014"></a><code>NNG_STAT_SCOPE</code>: <a name="NNG_STAT_SCOPE"></a>
+The statistic does not carry any real value, but is
+used for grouping related statistics together. This is a nexus in the
+statistics tree.</p>
+</li>
+<li>
+<p><a name="a015"></a><code>NNG_STAT_COUNTER</code>: <a name="NNG_STAT_COUNTER"></a>
+The statistic is a counter that only increments.
+Usually the change in the value of the statistic is more interesting
+(as a rate) than the absolute value at any given time. The value should
+be obtained using <a href="/api/stats.html#statistic-value"><code>nng_stat_value</code></a>.
+The units will be given by the value returned from <a href="/api/stats.html#statistic-units"><code>nng_stat_unit</code></a>.</p>
+</li>
+<li>
+<p><a name="a016"></a><code>NNG_STAT_LEVEL</code>: <a name="NNG_STAT_LEVEL"></a>
+The statistic represnts a measured value which corresponds
+to a specific value at a specific time. For example, this may represent the
+number of messages currently queued for some operation, or the link speed
+of a network interface. Most often the absolute value is more interesting
+than the change in the value over time. Again the value can be obtained with
+<a href="/api/stats.html#statistic-value"><code>nng_stat_value</code></a>, and any appropriate unit of measurement
+with <a href="/api/stats.html#statistic-units"><code>nng_stat_unit</code></a>.</p>
+</li>
+<li>
+<p><a name="a017"></a><code>NNG_STAT_STRING</code>: <a name="NNG_STAT_STRING"></a>
+The statistic is a string, such as a name. The value
+of the string can be obtained with <a href="/api/stats.html#statistic-value"><code>nng_stat_string</code></a>.
+The value of this string
+will remain valid until the snapshot is deallocated with <a href="/api/stats.html#freeing-a-snapshot"><code>nng_stats_free</code></a>.</p>
+</li>
+<li>
+<p><a name="a018"></a><code>NNG_STAT_BOOLEAN</code>: <a name="NNG_STAT_BOOLEAN"></a>
+The value of the statistic is a truth value (either <code>true</code>
+or <code>false</code>) and can be obtained with <a href="/api/stats.html#statistic-value"><code>nng_stat_bool</code></a>.</p>
+</li>
+<li>
+<p><a name="a019"></a><code>NNG_STAT_ID</code>: <a name="NNG_STAT_ID"></a>
+The value of the statistic is a numeric identifier, such as a socket
+identifier. The value can be obtained with <a href="/api/stats.html#statistic-value"><code>nng_stat_value</code></a>,
+and will be fixed for the life of the statistic.</p>
+</li>
+</ul>
+<h2 id="statistic-value"><a class="header" href="#statistic-value">Statistic Value</a></h2>
+<pre><code class="language-c">uint64_t nng_stat_value(const nng_stat *stat);
+const char *nng_stat_string(const nng_stat *stat);
+bool nng_stat_bool(const nng_stat *stat);
+</code></pre>
+<p>These functions return the value associated with the statistic.</p>
+<p>The <a name="a020"></a><code>nng_stat_value</code> function returns the the numeric value for the statistic <em>stat</em>
+of type <a href="/api/stats.html#NNG_STAT_COUNTER"><code>NNG_STAT_COUNTER</code></a>, <a href="/api/stats.html#NNG_STAT_LEVEL"><code>NNG_STAT_LEVEL</code></a>, or <a href="/api/stats.html#NNG_STAT_ID"><code>NNG_STAT_ID</code></a>.
+If <em>stat</em> is not one of these types, then it returns zero.</p>
+<p>The <a name="a021"></a><code>nng_stat_bool</code> function returns the Boolean value (either <code>true</code> or <code>false</code>) for the statistic <em>stat</em> of
+type <a href="/api/stats.html#NNG_STAT_BOOLEAN"><code>NNG_STAT_BOOLEAN</code></a>. If the statistics is not of this type, then it returns <code>false</code>.</p>
+<p>The <a name="a022"></a><code>nng_stat_string</code> function returns a pointer to a string value for the statistic <em>stat</em>,
+of type <a href="/api/stats.html#statistic-value"><code>NNG_STAT_STRING</code></a>. This string will remain valud until the snapshot that
+<em>stat</em> was collected with is deallocated with <a href="/api/stats.html#freeing-a-snapshot"><code>nng_stats_free</code></a>. If the statistic
+is not of type <code>NNG_STAT_STRING</code>, then <code>NULL</code> is returned.</p>
+<h2 id="statistic-units"><a class="header" href="#statistic-units">Statistic Units</a></h2>
+<pre><code class="language-c">int nng_stat_unit(const nng_stat *stat);
+</code></pre>
+<p>For statistics of type <a href="/api/stats.html#NNG_STAT_COUNTER"><code>NNG_STAT_COUNTER</code></a> or <a href="/api/stats.html#NNG_STAT_LEVEL"><code>NNG_STAT_LEVEL</code></a>,
+it is often useful to know what that quantity being reported measures.
+The following units may be returned from <a name="a023"></a><code>nng_stat_unit</code> for such a statistic:</p>
+<ul>
+<li><a name="a024"></a><code>NNG_UNIT_NONE</code>: No unit is known or applies.</li>
+<li><a name="a025"></a><code>NNG_UNIT_BYTES</code>: A count of bytes.</li>
+<li><a name="a026"></a><code>NNG_UNIT_MESSAGES</code>: A count of messages.</li>
+<li><a name="a027"></a><code>NNG_UNIT_MILLIS</code>: A count of milliseconds.</li>
+<li><a name="a028"></a><code>NNG_UNIT_EVENTS</code>: A count of events of some type.</li>
+</ul>
+<h2 id="statistic-timestamp"><a class="header" href="#statistic-timestamp">Statistic Timestamp</a></h2>
+<pre><code class="language-c">uint64_t nng_stat_timestamp(const nng_stat *stat);
+</code></pre>
+<p>Statistics have a timestamp indicating when the value was sampled,
+obtained via <a name="a029"></a><code>nng_stat_timestamp</code>. The timestamp is given in
+in milliseconds since a reference time, and the reference time used
+here is the same reference time used for <a href="/api/time.html#get-the-current-time"><code>nng_clock</code></a>.</p>
+<h2 id="see-also"><a class="header" href="#see-also">See Also</a></h2>
+<p><a href="/api/time.html#get-the-current-time"><code>nng_clock</code></a></p>
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