Setting Up A Global Logger


#1

I want to setup a global logger and write the logging messages into a file. Here is what I did for this purpose.

module Example

using Logging

function setlogger()
    io = open("/tmp/log.txt", "w+")
    logger = SimpleLogger(io)
    global_logger(logger)
    return nothing
end

function closelogger()
    close(global_logger().stream)
end

function test()
    setlogger()
    @info "Test message"
    @info "Test message"
    closelogger()
end

export setlogger, test, closelogger

end

and here is the console output when I tested logging

julia> using Example

julia> test()
[ Info: Test message
[ Info: Test message

The problem is that the logging messages are written into the console, not in the file /tmp/log.txt which is empty.
Any ideas what I am doing wrong?


#2

Your example works as expected for me:

julia> test()

shell> cat /tmp/log.txt
┌ Info: Test message
└ @ Main.Example REPL[1]:18
┌ Info: Test message
└ @ Main.Example REPL[1]:19

#3

Yes, it worked when I launched julia from terminal, using Example and calling test. But I realized that it does not work when I launch julia repl in Juno. Seems interesting to me. May be a kind of bug in Juno I think.


#4

Yeah, this is a Juno specific problem – we’re wrapping everything the user executes in a

with_logger(JunoProgressLogger(current_logger())) do 
  eval(usercode)
end

where the JunoProgressLogger delegates all log messages to the former current_logger. This means that the new global logger you set in your user code will never be used.

To solve that you could either set the global logger in an extra statement (which is obviously not a great solution) or just use with_logger in your code as well, which imho should be the preferred over messing around with global_logger anyways.


#5

Thank you for the reply. Yeah, with_logger is what I should use, though it is not a global logger, to work in Juno.
Here is the last case.

module Example

using Logging

function setlogger()
    io = open("/tmp/log.txt", "w+")
    SimpleLogger(io)
end

function test()
    logger = setlogger()
    with_logger(logger) do
        @info "Test message"
        @info "Test message"
    end
    flush(logger.stream)
end

export setlogger, test

end