docs: Add small description for pipe backend about distributor-threads

By default distributor-threads is a small number (currently 3). For
latency-bound applications this is too small, thus it would be a correct
place to have this description in pipe backend section as well.

Signed-off-by: Donatas Abraitis <donatas.abraitis@gmail.com>

diff --git a/docs/backends/pipe.rst b/docs/backends/pipe.rst
index 870329f5284d57eb706a9eeed4f5311c28ece38d..ad1febc39787673b8635f3d2c18020149d07d07d 100644 (file)
--- a/docs/backends/pipe.rst
+++ b/docs/backends/pipe.rst
@@ -17,6 +17,11 @@ The PipeBackend allows for easy dynamic resolution based on a
 'Coprocess' which can be written in any programming language that can
 read a question on standard input and answer on standard output.
 
+The number of distributor (backend) threads (``distributor-threads``) to start
+per receiver thread is low by default. This can impact the performance if
+you have latency-bound application as backend. You should increase the
+number of ``distributor-threads`` in such cases. See :doc:`performance`.
+
 The PipeBackend is primarily meant for allowing rapid development of new
 backends without tight integration with PowerDNS. It allows end-users to
 write PowerDNS backends in any language, a perl sample is provided. The