write_tsdb : Add a random TTL before querying the DNS again

[collectd.git] / src / collectd.conf.pod

diff --git a/src/collectd.conf.pod b/src/collectd.conf.pod
index 27c4e16..fce5903 100644 (file)
--- a/src/collectd.conf.pod
+++ b/src/collectd.conf.pod
@@ -8143,6 +8143,8 @@ packets.
 Synopsis:
 
  <Plugin write_tsdb>
+   DNS_Cache_TTL 60
+   DNS_Random_Cache_TTL 60
    <Node "example">
      Host "tsd-1.my.domain"
      Port "4242"
@@ -8151,7 +8153,34 @@ Synopsis:
  </Plugin>
 
 The configuration consists of one or more E<lt>B<Node>E<nbsp>I<Name>E<gt>
-blocks. Inside the B<Node> blocks, the following options are recognized:
+blocks and global directives.
+
+Global directives are:
+
+=over 4
+
+=item B<DNS_Cache_TTL> I<ttl>
+
+=item B<DNS_Random_Cache_TTL> I<ttl>
+
+When Collectd connects to a TSDB node, it will request the DNS. This can become
+a problem is the TSDN node is unavailable or badly configured because Collected
+will request DNS in order to reconnect for every metric, which can flood your DNS.
+So you can cache the last value for C<ttl> seconds (default: 600s e.g; 10 min).
+
+You can also define a random ttl. This prevents all your Collectd servers to
+request the DNS at the same time when the connection fails. Default value is
+15 * the write_tsdb interval (or the global interval if write_tsdb interval is not
+defined).
+
+Note : if the DNS resolution has already been successful, if the socket closes,
+the plugin will try to reconnect as soon as possible with the cached information.
+DNS is queried only when the socket is closed for a long time (DNS_Cache_TTL + 
+DNS_Random_Cache_TTL)
+
+=back
+
+Inside the B<Node> blocks, the following options are recognized:
 
 =over 4