futile.logger

futile.logger

Log4j-style logging for R.

Basic Usage

library(futile.logger)

# Log messages
flog.trace("Trace message")
flog.debug("Debug message")
flog.info("Info message")
flog.warn("Warning message")
flog.error("Error message")
flog.fatal("Fatal message")

Formatted Messages

# Printf-style formatting
flog.info("Processing file: %s", filename)
flog.info("Completed %d of %d items", current, total)
flog.info("Value: %.2f", value)

# Multiple arguments
flog.info("User %s performed action %s at %s", user, action, time)

Log Levels

# Set threshold
flog.threshold(INFO)   # Show INFO and above
flog.threshold(DEBUG)  # Show DEBUG and above
flog.threshold(WARN)   # Show WARN and above

# Get current threshold
flog.threshold()

# Log level constants
TRACE, DEBUG, INFO, WARN, ERROR, FATAL

Named Loggers

# Create named logger
flog.threshold(DEBUG, name = "myapp")
flog.info("Message", name = "myapp")

# Hierarchical loggers
flog.threshold(INFO, name = "myapp")
flog.threshold(DEBUG, name = "myapp.database")

# Child inherits from parent unless overridden
flog.info("DB query", name = "myapp.database")

Appenders

# Console (default)
flog.appender(appender.console())

# File
flog.appender(appender.file("app.log"))

# Tee (console and file)
flog.appender(appender.tee("app.log"))

# Multiple appenders
flog.appender(appender.tee("app.log"), name = "myapp")

# Custom appender
my_appender <- function(line) {
  # Custom logic
  cat(line, "\n")
}
flog.appender(my_appender)

Layouts

# Default layout
flog.layout(layout.simple)

# With timestamp
flog.layout(layout.format('[~t] [~l] ~m'))

# Custom format
# ~l = level
# ~t = timestamp
# ~n = namespace
# ~f = calling function
# ~m = message

flog.layout(layout.format('[~t] [~l] [~n] ~m'))

# JSON layout
flog.layout(layout.json)

# Tracing layout (includes function name)
flog.layout(layout.tracing)

Conditional Logging

# Check if level is enabled
if (flog.logger()$threshold <= DEBUG) {
  # Expensive debug computation
  flog.debug("Expensive: %s", expensive_computation())
}