Logger Middleware Documentation

MIDDLEWARE.md

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+# Echo Logger Middleware
+
+## Overview
+
+The Logger middleware for Echo is a powerful tool designed to log HTTP requests and responses. It's essential for debugging, monitoring application performance, and tracking user interactions with your Echo-based web services.
+
+## Features
+
+- Customizable log format
+- Support for multiple output destinations
+- Ability to skip logging for specific routes
+- Customizable timestamp format
+- Option to hide certain information (e.g., IP addresses)
+
+## Installation
+
+The Logger middleware is included in the Echo framework. To use it, you need to import Echo and its middleware package:
+
+```go
+import (
+    "github.com/labstack/echo/v4"
+    "github.com/labstack/echo/v4/middleware"
+)
+```
+
+## Basic Usage
+
+To add the Logger middleware to your Echo instance with default settings:
+
+```go
+e := echo.New()
+e.Use(middleware.Logger())
+```
+
+This will log requests and responses to the console (stdout) using the default format.
+
+## Configuration
+
+The Logger middleware can be customized using `LoggerConfig`. Here's an example of how to use it with custom settings:
+
+```go
+e.Use(middleware.LoggerWithConfig(middleware.LoggerConfig{
+    Format: "${time_custom} ${status} ${method} ${host}${path} ${latency_human}\n",
+    CustomTimeFormat: "2006-01-02 15:04:05.00000",
+}))
+```
+
+### Configuration Options
+
+- `Skipper` func(c echo.Context) bool
+  - Skipper defines a function to skip middleware execution.
+- `Format` string
+  - Format is the log format string.
+- `CustomTimeFormat` string
+  - CustomTimeFormat is the time format for ${time_custom}.
+- `Output` io.Writer
+  - Output is the writer where logs are written.
+
+### Available Format Fields
+
+- `${time_rfc3339}`
+- `${time_unix}`
+- `${time_unix_nano}`
+- `${time_custom}`
+- `${id}`
+- `${remote_ip}`
+- `${host}`
+- `${method}`
+- `${uri}`
+- `${path}`
+- `${protocol}`
+- `${referer}`
+- `${user_agent}`
+- `${status}`
+- `${error}`
+- `${latency}`
+- `${latency_human}`
+- `${bytes_in}`
+- `${bytes_out}`
+- `${header:<NAME>}`
+- `${query:<NAME>}`
+- `${form:<NAME>}`
+
+## Advanced Usage
+
+### Custom Output
+
+To log to a file instead of the console:
+
+```go
+logFile, err := os.OpenFile("server.log", os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
+if err != nil {
+    e.Logger.Fatal(err)
+}
+e.Use(middleware.LoggerWithConfig(middleware.LoggerConfig{
+    Output: logFile,
+}))
+```
+
+### Skipping Specific Routes
+
+To skip logging for certain routes:
+
+```go
+e.Use(middleware.LoggerWithConfig(middleware.LoggerConfig{
+    Skipper: func(c echo.Context) bool {
+        return c.Path() == "/health"
+    },
+}))
+```
+
+### Custom Log Format
+
+For a more detailed log format:
+
+```go
+e.Use(middleware.LoggerWithConfig(middleware.LoggerConfig{
+    Format: "${time_rfc3339_nano} ${id} ${remote_ip} ${host} ${method} ${uri} ${user_agent}" +
+        " ${status} ${error} ${latency_human}" +
+        " ${bytes_in} ${bytes_out}\n",
+}))
+```
+
+## Best Practices
+
+1. Use a custom format that includes all necessary information for your use case.
+2. Consider using a separate log file for HTTP requests to avoid cluttering your main application logs.
+3. In production environments, use a log aggregation service to centralize and analyze your logs.
+4. Be mindful of sensitive information in your logs, especially when logging headers or form data.
+
+## Performance Considerations
+
+While the Logger middleware is designed to be efficient, logging every request can impact performance in high-traffic scenarios. Consider the following:
+
+- Use sampling in production for very high-traffic services.
+- Benchmark your application with and without the Logger middleware to understand its impact.
+
+## Conclusion
+
+The Echo Logger middleware is a flexible and powerful tool for monitoring and debugging your web applications. By customizing its configuration, you can tailor the logging to your specific needs while maintaining high performance.