Issue while changing log level at runtime

[skeleton18]

Hello,
I'm trying to change log levels at runtime but it is not working as I expected.
I am using spdlog 1.9.2.

Here is what I have done :

1/ In my header file I have just define SPDLOG_ACTIVE_LEVEL to SPDLOG_LEVEL_TRACE before including spdlog/spdlog.h.

2/ Then I declare 3 loggers:

1. A default console logger spdlog::stdout_color_mt("default") set with level spdlog::level::debug
2. An error console logger spdlog::stderr_color_mt("errorLogger") set with level spdlog::level::warn
3. A file logger spdlog::basic_logger_mt("fileLogger", "logs/basic-log.txt", true) set with level spdlog::level::trace

3/ Finally I wrote a simple main to log messages for each log level (trace, debug, info, warn, error and critical) using SPDLOG_LOGGER_XXX macros.

When I run my main program setting export SPDLOG_LEVEL="*=off,default=warn" (i.e. disable all loggers but default, and change its log level to warn), it does not seem to work because I had the following output:

[2021-12-21 11:29:28.664 +01:00] [default] [Logger.h] [debug] [thread #3969739] Testing trace
[2021-12-21 11:29:28.664 +01:00] [default] [Logger.h] [info] [thread #3969739] Testing trace
[2021-12-21 11:29:28.664 +01:00] [errorLogger] [Logger.h] [warning] [thread #3969739] Testing trace
[2021-12-21 11:29:28.665 +01:00] [default] [Logger.h] [warning] [thread #3969739] Testing trace
[2021-12-21 11:29:28.665 +01:00] [errorLogger] [Logger.h] [error] [thread #3969739] Testing trace
[2021-12-21 11:29:28.665 +01:00] [default] [Logger.h] [error] [thread #3969739] Testing trace
[2021-12-21 11:29:28.665 +01:00] [errorLogger] [Logger.h] [critical] [thread #3969739] Testing trace
[2021-12-21 11:29:28.665 +01:00] [default] [Logger.h] [critical] [thread #3969739] Testing trace

What do I do wrong ?
Thanks for the help.

[tt4g]

The first *= is not necessary.

- export SPDLOG_LEVEL="*=off,default=warn"
+ export SPDLOG_LEVEL="off,default=warn"

And should call spdlog::cfg::load_env_levels() to load log level from environment variable SPDLOG_LEVEL.

[skeleton18]

Thank you for the quick answer.

Indeed, without the *= at the beginning, it works perfectly when I call the spdlog::cfg::load_env_levels() function before logging.

Just one more question, let's imagine that I set SPDLOG_LEVEL to "off,default=warn" and then I launch my service.
If I just want to change at runtime, the log level of fileLogger, Can I just set SPDLOG_LEVEL to fileLogger=info or do I need to set full configuration with off,default=warn,fileLogger=info?

[tt4g]

do I need to set full configuration with off,default=warn,fileLogger=info?

Yes. If a global level is specified in SPDLOG_LEVEL, then any logger that does not have a logger name and log level pair specified will have its global log level set.

Another thing to note is that SPDLOG_LEVEL only accepts a maximum of 512 characters: https://github.com/gabime/spdlog/blob/v1.9.2/include/spdlog/cfg/helpers-inl.h#L82-L87
This restriction makes it difficult to control the log level of many loggers with SPDLOG_LEVEL.