[erlang-questions] Erlang 21 Logger Configuration

[Steve Strong]

Hi All,

Quick question regarding the handling of configuration changes for the disk_log hander in the new Logger framework, and specifically how it handles max_no_bytes.

Given a clean directory, I can do the following:

> erl
Erlang/OTP 21 [erts-10.3] [source] [64-bit] [smp:12:12] [ds:12:12:10] [async-threads:1] [hipe]

Eshell V10.3  (abort with ^G)
1> logger:add_handler(disk_log, logger_disk_log_h, #{config => #{file => "log/debug.log", type => wrap, max_no_files => 10, max_no_bytes => 10000}, level => all}).
ok
2>q().

That creates me a log folder with a debug.log.1, debug.log.idx and debug.log.siz.  If I then start a new shell and try to create the handler but with a different max_no_bytes, I get the following:

> erl
Erlang/OTP 21 [erts-10.3] [source] [64-bit] [smp:12:12] [ds:12:12:10] [async-threads:1] [hipe]

Eshell V10.3  (abort with ^G)
1> logger:add_handler(disk_log, logger_disk_log_h, #{config => #{file => "log/debug.log", type => wrap, max_no_files => 10, max_no_bytes => 15000}, level => all}).
{error,{handler_not_added,{size_mismatch,{10000,10},
                                         {15000,10}}}}
2> q().

Due to the change in the max_no_bytes parameter, the handler fails to start.  What is the recommended way to deal with adjusting config value such as this, particularly for handlers that may be added / removed dynamically?  Right now, we are needing to archive the entire log directory prior to changing values, which is a real pain.  


Cheers,

Steve
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