document logging

Refs #1494

docs/running-in-production.rst

@@ -0,0 +1,20 @@
+Running in production
+=====================
+
+Logging
+-------
+
+Default logging level (``main:info,state:info,*:``) should suffice for normal
+operation mode. Read `this post
+<https://blog.cosmos.network/one-of-the-exciting-new-features-in-0-10-0-release-is-smart-log-level-flag-e2506b4ab756>__`
+for details on how to configure ``log_level`` config variable. Some of the
+modules can be found `here <./how-to-read-logs.html#list-of-modules>__`.
+
+If you're trying to debug Tendermint or asked to provide logs with debug
+logging level, you can do so by running tendermint with
+``--log_level="*:debug"``.
+
+Consensus WAL
+-------------
+
+Consensus module writes every message to the WAL (write-ahead log).