bondscell_results $e1be3bfb-0764-435d-872f-e073ca3c3ee8queued¤logslinemsgThis is an error messagetext/plaincell_id$e1be3bfb-0764-435d-872f-e073ca3c3ee8kwargsidMain_workspace#2_52445b6efilep/home/runner/work/JuliaWorkshopAISF/JuliaWorkshopAISF/Lesson2/logging.jl#==#e1be3bfb-0764-435d-872f-e073ca3c3ee8grouplogginglevelErrorlinemsgThis is a warn messagetext/plaincell_id$e1be3bfb-0764-435d-872f-e073ca3c3ee8kwargsidMain_workspace#2_b16ebfe9filep/home/runner/work/JuliaWorkshopAISF/JuliaWorkshopAISF/Lesson2/logging.jl#==#e1be3bfb-0764-435d-872f-e073ca3c3ee8grouplogginglevelWarnlinemsgThis is an info messagetext/plaincell_id$e1be3bfb-0764-435d-872f-e073ca3c3ee8kwargsidMain_workspace#2_6f42f2f9filep/home/runner/work/JuliaWorkshopAISF/JuliaWorkshopAISF/Lesson2/logging.jl#==#e1be3bfb-0764-435d-872f-e073ca3c3ee8grouplogginglevelInfolinemsgThis is a debug messagetext/plaincell_id$e1be3bfb-0764-435d-872f-e073ca3c3ee8kwargsidMain_workspace#2_2151730cfilep/home/runner/work/JuliaWorkshopAISF/JuliaWorkshopAISF/Lesson2/logging.jl#==#e1be3bfb-0764-435d-872f-e073ca3c3ee8grouplogginglevelDebugrunning¦outputbodymimetext/plainrootassigneelast_run_timestampAj)|persist_js_state·has_pluto_hook_features§cell_id$e1be3bfb-0764-435d-872f-e073ca3c3ee8depends_on_disabled_cells§runtime !published_object_keysdepends_on_skipped_cells§errored$9117b3c6-80af-463d-8e4d-a35bef1023acqueued¤logsrunning¦outputbodyٸTransformerLogger
This allows to transform the log received, not just the log message. A nice example is to add the time to the log message
TeeLogger
There are many Loggers defined in LoggingExtras and we probably won't have time to go through all of them. Let's start with the TeeLogger or demux, this simply reroutes the log messages to different loggers. The interface of the constructor is:
TeeLogger(loggers::AbstractLogger...)
and the log message will be passed to all the loggers passed. A possible usage of it could be to print the debug messages in a different place respect to the info messages, in this way we would have a more clean space where we have only the imporant messages, and another place where we have detailed informations about the running code.
FileLogger
This logs to a file, let's see a more complex exampl combining the previous types
julia> using LoggingExtras;
julia> demux_logger = TeeLogger(
MinLevelLogger(FileLogger("info.log"), Logging.Info),
MinLevelLogger(FileLogger("warn.log"), Logging.Warn),
);
julia> with_logger(demux_logger) do
@warn("It is bad")
@info("normal stuff")
@error("THE WORSE THING")
@debug("it is chill")
end
shell> cat warn.log
┌ Warning: It is bad
└ @ Main REPL[34]:2
┌ Error: THE WORSE THING
└ @ Main REPL[34]:4
shell> cat info.log
┌ Warning: It is bad
└ @ Main REPL[34]:2
┌ Info: normal stuff
└ @ Main REPL[34]:3
┌ Error: THE WORSE THING
└ @ Main REPL[34]:4
Note
Pluto doesn't allow to set the global logger since each cell is evaluated with a different logger, but the function global_logger([logger]) returns the current global logger, and if a logger is passed as argument, the global logger is changed.
MinLevelLogger
This is a special case of the early filtered logger that checks if the message level is above the level specified when created.
ActiveFilteredLogger
This allows to only select some log messages to show based on a filter function
EarlyFilteredLogger
This is similar to the ActiveFilteredLogger but the filter function is called before the log message is generated so the filter cannot be based on it, but it can still access:
level the level of the log
module which module called the logger
id this is a unique identifier of the message
Logging
Logging is very important when writing code, logged messages are used to track the execution of the program, also allowing to more simply identify bugs and debug them.
Julia has two main libraries for logging, the base one Logging and an extended version LoggingExtras.
The main types of logging are:
We can decide which is the minimul level to log, the important thing is that the code below that thersold will not get executed, this allows to mark as debug some expensive checks that we want to perform only when we are performing a debug.
We can also add an exception and a backtrace to the @error macro, it is important to know that the exception would not be thrown automatically. This allows to know if an error occurred by reading the log even if the error was catched.
Log a message
To log a message, we just need to use the macros @error, @warn, @info and @debug, followed by the message we wish to show
This is the usual setup I use in my own code:
using LoggingExtras, Dates
const date_format = "yyyy-mm-dd HH:MM:SS"
timestamp_logger(logger) =
TransformerLogger(logger) do log
merge(log, (; message="[$(Dates.format(now(), date_format))] $(log.message)"))
end
demux_logger(infoFileName::AbstractString, debugFileName::AbstractString) = TeeLogger(
MinLevelLogger(FileLogger("$infoFileName.info.log"; append=true), Logging.Info),
MinLevelLogger(FileLogger("$debugFileName.debug.log"; append=true), Logging.Debug),
);
demux_logger(str::AbstractString) = demux_logger(str, str)
demux_logger(joinpath(folder_name, baseFilename)) |> timestamp_logger |> global_logger
we can also add variables to it that will be shown togheter with the message, this is very useful when debugging