Merge pull request #2910 from vespa-engine/hmusum/document-forwarded-…

…log-message-and-how-to-configure

Document in more detail what is sent to log archive and how to config…

en/reference/logs.html

@@ -234,7 +234,8 @@ <h2 id="log-events">Log events</h2>
 <h2 id="logd">Logd</h2>
 <p>
 A small program named <em>logd</em> is responsible for rotating the
-<code>vespa.log</code> file and also forwarding it to the log server.
+<code>vespa.log</code> file and also forwarding most log messages
+(see next section for details) to the log server.
 The log file is rotated after 24 hours, or if it grows too large.
 Rotated logs are removed by logd after 30 days, or if the total size
 grows above 1000 MB.
@@ -271,8 +272,9 @@ <h2 id="log-server">Log server</h2>
 {% include note.html content="If you need to remove log files more aggressively than this to e.g. prevent
 running out of storage space, you need to add a way of purging log files no longer needed yourself."%}
 <p>
-Events are normally filtered before sending to the log archive.
-To forward, add to <em>services.xml</em>:
+Events and log messages with level <em>debug</em> and <em>spam</em> are normally filtered out
+before sending to the log archive.
+As an example, to forward events and <em>debug</em> log messages, add this to <em>services.xml</em>:
 </p>
 <pre>
 &lt;services&gt;
@@ -281,6 +283,9 @@ <h2 id="log-server">Log server</h2>
             &lt;event&gt;
                 &lt;forward&gt;true&lt;/forward&gt;
             &lt;/event&gt;
+            &lt;debug&gt;
+                &lt;forward&gt;true&lt;/forward&gt;
+            &lt;/debug&gt;
         &lt;/loglevel&gt;
     &lt;/config&gt;
 </pre>