terry-xiaoyu 2269967f1a Lazy evaluation when logging messages ... Formatting variables and then passing them into the logger functions leads to performance issues. i.e. ```erlang logger:debug("RECV ~s", [emqx_packet:format(Packet)]) ``` Above message will only be printed when the current log level set to `debug`, but the function emqx_packet:format/1 will always be evaluated no matter what the current log level is. OTP 21 provides a special meta-data named `report_cb`, which can be used for lazy evaluation. The fun is only evaluated if the primary/handler log level check passes, and is therefore recommended if it is expensive to generate the message.		2018-11-19 11:17:58 +08:00
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emqx.schema	Lazy evaluation when logging messages	2018-11-19 11:17:58 +08:00