Format LogEvents as JSON

A format for formatting LogEvents as jsonlines log files. This provides a nice balance between human- an machine-readability.

See also

read_json_lines(), https://jsonlines.org/

Other Layouts: Layout, LayoutFormat, LayoutGlue

Super class

lgr::Layout -> LayoutJson

Active bindings

toJSON_args

a list of values passed on to jsonlite::toJSON()

timestamp_fmt

Used by $format_event() to format timestamps.

Methods

Public methods

• LayoutJson$new()

• LayoutJson$format_event()

• LayoutJson$set_toJSON_args()

• LayoutJson$set_timestamp_fmt()

• LayoutJson$toString()

• LayoutJson$parse()

• LayoutJson$read()

• LayoutJson$clone()

---

Method new()

Usage

LayoutJson$new(toJSON_args = list(auto_unbox = TRUE), timestamp_fmt = NULL)

---

Method format_event()

Usage

LayoutJson$format_event(event)

---

Method set_toJSON_args()

Set arguments to pass on to jsonlite::toJSON()

Usage

LayoutJson$set_toJSON_args(x)

Arguments

x

a named list

---

Method set_timestamp_fmt()

Set a format that this Layout will apply to timestamps.

Usage

LayoutJson$set_timestamp_fmt(x)

Arguments

x

• NULL (the default): formatting of the timestamp is left to jsonlite::toJSON(),

• a character scalar as for format.POSIXct(), or

• a function that returns a vector of the same length as its (POSIXct) input. The returned vector can be of any type supported by jsonlite::toJSON(), but should usually be character.

---

Method toString()

Usage

LayoutJson$toString()

---

Method parse()

Usage

LayoutJson$parse(file)

---

Method read()

Usage

LayoutJson$read(file, threshold = NA_integer_, n = 20L)

---

Method clone()

The objects of this class are cloneable with this method.

Usage

LayoutJson$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

Examples

# setup a dummy LogEvent
event <- LogEvent$new(
  logger = Logger$new("dummy logger"),
  level = 200,
  timestamp = Sys.time(),
  caller = NA_character_,
  msg = "a test message",
  custom_field = "LayoutJson can handle arbitrary fields"
)

# Default settings show all event fals
lo <- LayoutJson$new()
lo$format_event(event)
#> {"level":200,"timestamp":"2025-04-14 20:58:45","logger":"dummy logger","caller":null,"msg":"a test message","custom_field":"LayoutJson can handle arbitrary fields"}