+default) counter values are stored as is, i.e. as an increasing integer number.
+
+=item B<BufferSize> I<Bytes>
+
+Sets the send buffer size to I<Bytes>. By increasing this buffer, less HTTP
+requests will be generated, but more metrics will be batched / metrics are
+cached for longer before being sent, introducing additional delay until they
+are available on the server side. I<Bytes> must be at least 1024 and cannot
+exceed the size of an C<int>, i.e. 2E<nbsp>GByte.
+Defaults to C<4096>.
+
+=item B<LowSpeedLimit> I<Bytes per Second>
+
+Sets the minimal transfer rate in I<Bytes per Second> below which the
+connection with the HTTP server will be considered too slow and aborted. All
+the data submitted over this connection will probably be lost. Defaults to 0,
+which means no minimum transfer rate is enforced.
+
+=item B<Timeout> I<Timeout>
+
+Sets the maximum time in milliseconds given for HTTP POST operations to
+complete. When this limit is reached, the POST operation will be aborted, and
+all the data in the current send buffer will probably be lost. Defaults to 0,
+which means the connection never times out.
+
+=item B<LogHttpError> B<false>|B<true>
+
+Enables printing of HTTP error code to log. Turned off by default.
+
+The C<write_http> plugin regularly submits the collected values to the HTTP
+server. How frequently this happens depends on how much data you are collecting
+and the size of B<BufferSize>. The optimal value to set B<Timeout> to is
+slightly below this interval, which you can estimate by monitoring the network
+traffic between collectd and the HTTP server.
+
+=back
+
+=head2 Plugin C<write_kafka>
+
+The I<write_kafka plugin> will send values to a I<Kafka> topic, a distributed
+queue.
+Synopsis:
+
+ <Plugin "write_kafka">
+ Property "metadata.broker.list" "broker1:9092,broker2:9092"
+ <Topic "collectd">
+ Format JSON
+ </Topic>
+ </Plugin>
+
+The following options are understood by the I<write_kafka plugin>:
+
+=over 4
+
+=item E<lt>B<Topic> I<Name>E<gt>
+
+The plugin's configuration consists of one or more B<Topic> blocks. Each block
+is given a unique I<Name> and specifies one kafka producer.
+Inside the B<Topic> block, the following per-topic options are
+understood:
+
+=over 4
+
+=item B<Property> I<String> I<String>
+
+Configure the named property for the current topic. Properties are
+forwarded to the kafka producer library B<librdkafka>.
+
+=item B<Key> I<String>
+
+Use the specified string as a partioning key for the topic. Kafka breaks
+topic into partitions and guarantees that for a given topology, the same
+consumer will be used for a specific key. The special (case insensitive)
+string B<Random> can be used to specify that an arbitrary partition should
+be used.
+
+=item B<Format> B<Command>|B<JSON>|B<Graphite>
+
+Selects the format in which messages are sent to the broker. If set to
+B<Command> (the default), values are sent as C<PUTVAL> commands which are
+identical to the syntax used by the I<Exec> and I<UnixSock plugins>.
+
+If set to B<JSON>, the values are encoded in the I<JavaScript Object Notation>,
+an easy and straight forward exchange format.
+
+If set to B<Graphite>, values are encoded in the I<Graphite> format, which is
+C<E<lt>metricE<gt> E<lt>valueE<gt> E<lt>timestampE<gt>\n>.
+
+=item B<StoreRates> B<true>|B<false>
+
+Determines whether or not C<COUNTER>, C<DERIVE> and C<ABSOLUTE> data sources
+are converted to a I<rate> (i.e. a C<GAUGE> value). If set to B<false> (the
+default), no conversion is performed. Otherwise the conversion is performed
+using the internal value cache.
+
+Please note that currently this option is only used if the B<Format> option has
+been set to B<JSON>.
+
+=item B<GraphitePrefix> (B<Format>=I<Graphite> only)
+
+A prefix can be added in the metric name when outputting in the I<Graphite>
+format. It's added before the I<Host> name.
+Metric name will be
+C<E<lt>prefixE<gt>E<lt>hostE<gt>E<lt>postfixE<gt>E<lt>pluginE<gt>E<lt>typeE<gt>E<lt>nameE<gt>>
+
+=item B<GraphitePostfix> (B<Format>=I<Graphite> only)
+
+A postfix can be added in the metric name when outputting in the I<Graphite>
+format. It's added after the I<Host> name.
+Metric name will be
+C<E<lt>prefixE<gt>E<lt>hostE<gt>E<lt>postfixE<gt>E<lt>pluginE<gt>E<lt>typeE<gt>E<lt>nameE<gt>>
+
+=item B<GraphiteEscapeChar> (B<Format>=I<Graphite> only)
+
+Specify a character to replace dots (.) in the host part of the metric name.
+In I<Graphite> metric name, dots are used as separators between different
+metric parts (host, plugin, type).
+Default is C<_> (I<Underscore>).
+
+=item B<GraphiteSeparateInstances> B<false>|B<true>
+
+If set to B<true>, the plugin instance and type instance will be in their own
+path component, for example C<host.cpu.0.cpu.idle>. If set to B<false> (the
+default), the plugin and plugin instance (and likewise the type and type
+instance) are put into one component, for example C<host.cpu-0.cpu-idle>.
+
+=item B<StoreRates> B<true>|B<false>
+
+If set to B<true> (the default), convert counter values to rates. If set to
+B<false> counter values are stored as is, i.e. as an increasing integer number.
+
+This will be reflected in the C<ds_type> tag: If B<StoreRates> is enabled,
+converted values will have "rate" appended to the data source type, e.g.
+C<ds_type:derive:rate>.
+
+=back
+
+=item B<Property> I<String> I<String>
+
+Configure the kafka producer through properties, you almost always will
+want to set B<metadata.broker.list> to your Kafka broker list.
+
+=back
+
+=head2 Plugin C<write_redis>
+
+The I<write_redis plugin> submits values to I<Redis>, a data structure server.
+
+Synopsis:
+
+ <Plugin "write_redis">
+ <Node "example">
+ Host "localhost"
+ Port "6379"
+ Timeout 1000
+ Prefix "collectd/"
+ Database 1
+ </Node>
+ </Plugin>
+
+Values are submitted to I<Sorted Sets>, using the metric name as the key, and
+the timestamp as the score. Retrieving a date range can then be done using the
+C<ZRANGEBYSCORE> I<Redis> command. Additionally, all the identifiers of these
+I<Sorted Sets> are kept in a I<Set> called C<collectd/values> (or
+C<${prefix}/values> if the B<Prefix> option was specified) and can be retrieved
+using the C<SMEMBERS> I<Redis> command. You can specify the database to use
+with the B<Database> parameter (default is C<0>). See
+L<http://redis.io/commands#sorted_set> and L<http://redis.io/commands#set> for
+details.
+
+The information shown in the synopsis above is the I<default configuration>
+which is used by the plugin if no configuration is present.
+
+The plugin can send values to multiple instances of I<Redis> by specifying
+one B<Node> block for each instance. Within the B<Node> blocks, the following
+options are available:
+
+=over 4
+
+=item B<Node> I<Nodename>
+
+The B<Node> block identifies a new I<Redis> node, that is a new I<Redis>
+instance running on a specified host and port. The node name is a
+canonical identifier which is used as I<plugin instance>. It is limited to
+51E<nbsp>characters in length.
+
+=item B<Host> I<Hostname>
+
+The B<Host> option is the hostname or IP-address where the I<Redis> instance is
+running on.
+
+=item B<Port> I<Port>
+
+The B<Port> option is the TCP port on which the Redis instance accepts
+connections. Either a service name of a port number may be given. Please note
+that numerical port numbers must be given as a string, too.
+
+=item B<Timeout> I<Milliseconds>
+
+The B<Timeout> option sets the socket connection timeout, in milliseconds.
+
+=item B<Prefix> I<Prefix>
+
+Prefix used when constructing the name of the I<Sorted Sets> and the I<Set>
+containing all metrics. Defaults to C<collectd/>, so metrics will have names
+like C<collectd/cpu-0/cpu-user>. When setting this to something different, it
+is recommended but not required to include a trailing slash in I<Prefix>.
+
+=item B<Database> I<Index>
+
+This index selects the redis database to use for writing operations. Defaults to C<0>.