How Can I Dynamically Update Log Levels with Zap Logger in Controller-Runtime?

Dynamic Log Level Updates with Zap Logger in Controller-Runtime

Context

Zap, a popular logging library in Go, allows for configurable logging behavior. In this case, the logger is initialized by the kubebuilder utility, which uses Zap as its underlying logging mechanism. The task at hand is to dynamically adjust the log level of the running application at runtime while maintaining the use of the sigs.k8s.io/controller-runtime/pkg/log/zap library.

Solution

The sigs.k8s.io/controller-runtime/pkg/log/zap library does not provide a straightforward API to update the log level at runtime. However, Zap offers a solution through its zap.NewAtomicLevel() function. This function creates an atomic level that can be dynamically set at runtime, as demonstrated in the following code snippet:

import (
    "go.uber.org/zap"
    "go.uber.org/zap/zapcore"
)

func main() {
    // Create an atomic level.
    atom := zap.NewAtomicLevel()

    // Configure the logger with the atomic level.
    logger := zap.New(zapcore.NewCore(
        zapcore.NewJSONEncoder(zapcore.NewProductionEncoderConfig()),
        zapcore.Lock(os.Stdout),
        atom,
    ))

    // Set initial log level.
    atom.SetLevel(zapcore.InfoLevel)

    // Log a message at the set level.
    logger.Info("Info message")

    // Change the log level at runtime.
    atom.SetLevel(zapcore.ErrorLevel)

    // Log another message at the new level.
    logger.Info("Info message after level change")
}

Implementation for Controller-Runtime

To implement this solution in the context of controller-runtime, replace the existing ctrl.SetLogger call with the following modified code:

// Initialize the atomic level.
atom := zap.NewAtomicLevel()

// Configure the logger with the atomic level.
logger := zap.New(zapcore.NewCore(
    zapcore.NewJSONEncoder(zapcore.NewProductionEncoderConfig()),
    zapcore.Lock(os.Stdout),
    atom,
))

// Bind the flags to the options.
opts.BindFlags(flag.CommandLine)
flag.Parse()

// Set the logger with the modified options and atomic level.
ctrl.SetLogger(logger, opts)

This modification ensures that the logger initialized by kubebuilder utilizes the atomic level, allowing you to dynamically update the log level at runtime.

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