LogEvent: Events - The Atomic Unit of Logging

Description

A LogEvent is a single unit of data that should be logged. LogEvents are usually created by a Logger, and then processed by Appenders.

Arguments

Usage

x <- LogEvent$new(logger, level = 400, timestamp = Sys.time(), caller = NA, msg
  = NA, ...)
x$clone(deep = FALSE)
x$.logger
x$caller
x$level
x$level_name
x$logger
x$msg
x$timestamp
x$values

Creating LogEvents / Fields

The arguments to LogEvent$new() directly translate to the fields stored in the LogEvent:

level: integer: the log_level / priority of the LogEvent
timestamp: POSIXct the time when then the LogEvent was created
caller: character. The name of the calling function
msg: character. A message
logger: character scalar. Name of the Logger that created the event (.logger$full_name)
user: character scalar. User as set for the Logger that created this event (.logger$user)
.logger: a Logger. A reference to the Logger that created the event
...: 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 an Appender that supports custom fields quite naturally.

Usually the above 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.

Active Bindings

LogEvents contain some some active bindings that make it easier to retrieve commonly used values.

level_name: character: the log_level / priority of the LogEvent labelled according to getOption("lgr.log_levels")
values: list: All values stored in the LogEvent (including all custom fields, but not including event$logger)
logger_name: character scalar: The name of the Logger that created this event, equivalent to event$logger$name)
logger_user: character scalar: The user of the Logger that created this event, equivalent to event$logger_user)

Examples

Run this code

# NOT RUN {
l <- Logger$new("dummy logger", appenders = NULL)
l$error("foo bar")

# The last LogEvent produced by a Logger is stored in the last_event field
l$last_event  # formatted by default
l$last_event$values  # values stored in the event

# Also contains the Logger that created it as .logger
l$last_event$logger
# equivalent to
l$last_event$.logger$name

# This is really a reference to the complete Logger, so the following is
# possible (though nonsensical)
l$last_event$.logger$last_event$msg
identical(l, l$last_event$.logger)

# }