api_logger: Set logging function and access log format for the API

In plumber2: Easy and Powerful Web Servers

Set logging function and access log format for the API

Description

plumber2 has a build-in logging facility that takes care of logging any conditions that are caught, as well as access logs. Further it is possible to log custom messages using the log() method on the api object. However, the actual logging is handled by a customizable function that can be set. You can read more about the logging infrastructure in the fiery documentation. plumber2 reexports the loggers provided by fiery so they are immediately available to the user.

Usage

api_logger(api, logger = NULL, access_log_format = NULL)

logger_null()

logger_console(format = "{time} - {event}: {message}")

logger_file(file, format = "{time} - {event}: {message}")

logger_logger(default_level = "INFO")

logger_otel(format = "{message}")

logger_switch(..., default = logger_null())

common_log_format

combined_log_format

Arguments

api	A plumber2 api object to set the logger on
logger	A logger function. If NULL then the current logger is kept
access_log_format	A glue string giving the format for the access logs. plumber2 (through fiery) provides the predefined common_log_format and combined_log_format, but you can easily create your own. See fiery::loggers for which variables the glue string has access to.
format	A glue-like string specifying the format of the log entry. Only the variables time, event, and message are available and must be given verbatim
file	A file or connection to write to
default_level	The log level to use for events that are not request, websocket, message, warning, or error
...	A named list of loggers to use for different events. The same semantics as switch is used so it is possible to let events fall through e.g. logger_switch(error =, warning = logger_file('errors.log')).
default	A catch-all logger for use with events not defined in ...

Using annotation

Logger setup doesn't have a dedicated annotation tag, but you can set it up in a ⁠@plumber⁠ block

#* @plumber
function(api) {
  api |>
    api_logger(logger = logger_null())
}

Examples

# Use a different access log format
api() |>
  api_logger(access_log_format = combined_log_format)

# Turn off logging
api() |>
  api_logger(logger_null())

plumber2 documentation built on Jan. 20, 2026, 5:06 p.m.