LogEvents - The atomic unit of logging

A LogEvent is a single unit of data that should be logged. LogEvents are usually created by a Logger, and then processed by one more Appenders. They do not need to be instantiated manually except for testing and experimentation; however, if you plan on writing your own Appenders or Layouts you need to understand LogEvents.

See also

as.data.frame.LogEvent()

Other docs relevant for extending lgr: as_LogEvent(), event_list(), standardize_threshold()

Public fields

level

integer. The log_level / priority of the LogEvent. Use the active binding level_name to get the character representation instead.

timestamp

POSIXct. The time when then the LogEvent was created.

caller

character. The name of the calling function.

msg

character. The log message.

.logger

Logger. A reference to the Logger that created the event (equivalent to get_logger(event$logger)).

Active bindings

values

list. All values stored in the LogEvent, including all custom fields, but not including event$.logger.

level_name

character. The log_level / priority of the LogEvent labelled according to getOption("lgr.log_levels")

logger

character scalar. The name of the Logger that created this event, equivalent to event$.logger$name)

Methods

Public methods

• LogEvent$new()

• LogEvent$clone()

---

Method new()

The arguments to LogEvent$new() directly translate to the fields stored in the LogEvent. Usually these values will be scalars, but (except for "logger") they can also be vectors if they are all of the same length (or scalars that will be recycled). In this case the event will be treated by the Appenders and Layouts as if several separate events.

Usage

LogEvent$new(
  logger,
  level = 400,
  timestamp = Sys.time(),
  caller = NA,
  msg = NA,
  ...
)

Arguments

logger, level, timestamp, caller, msg

see Public fields.

...

All named arguments in ... will be added to the LogEvent as custom fields. You can store arbitrary R objects in LogEvents this way, but not all Appenders will support them. See AppenderJson for

---

Method clone()

The objects of this class are cloneable with this method.

Usage

LogEvent$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

Examples

lg <- get_logger("test")
lg$error("foo bar")
#> ERROR [20:58:45.482] foo bar

# The last LogEvent produced by a Logger is stored in its `last_event` field
lg$last_event  # formatted console output
#> ERROR [2025-04-14 20:58:45] foo bar
lg$last_event$values  # values stored in the event
#> $level
#> [1] 200
#> 
#> $timestamp
#> [1] "2025-04-14 20:58:45 UTC"
#> 
#> $logger
#> [1] "test"
#> 
#> $caller
#> [1] "eval"
#> 
#> $msg
#> [1] "foo bar"
#> 

# Also contains the Logger that created it as .logger
lg$last_event$logger
#> [1] "test"
# equivalent to
lg$last_event$.logger$name
#> [1] "test"

# This is really a reference to the complete Logger, so the following is
# possible (though nonsensical)
lg$last_event$.logger$last_event$msg
#> [1] "foo bar"
identical(lg, lg$last_event$.logger)
#> [1] TRUE
lg$config(NULL)  # reset logger config
#> <Logger> [info] test
#> 
#> inherited appenders:
#>   console: <AppenderConsole> [all] -> console