Document keepalive for buildbot workers may be the reason for frequent disconnects (#1221)

Co-authored-by: Ezio Melotti <ezio.melotti@gmail.com>

Author: brettcannon

testing/new-buildbot-worker.rst

@@ -195,6 +195,13 @@ by tests that fail.  Unfortunately we do not currently have a way to notify you
 only of failures on your builders, so doing periodic spot checks is also a good
 idea.
 
+.. note::
+   If your buildbot worker is disconnecting regularly, it may be a symptom of the
+   default ``keepalive`` value (``600`` for 10 minutes) being `set
+   <https://docs.buildbot.net/latest/manual/installation/worker.html#cmdoption-buildbot-worker-create-worker-keepalive>`_
+   too high. You can change it to a lower value (e.g. ``180`` for 3 minutes)
+   in the ``buildbot.tac`` file found in your build area.
+
 
 Latent workers
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