JSON Logging

This example demonstrates how to enable JSON logging with colors and use context binding. JSON logging is essential for modern log aggregation systems like ELK, Datadog, or CloudWatch.

Code Example

const std = @import("std");
const logly = @import("logly");

pub fn main() !void {
    // Enable ANSI colors on Windows
    _ = logly.Terminal.enableAnsiColors();

    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
    defer _ = gpa.deinit();
    const allocator = gpa.allocator();

    const logger = try logly.Logger.init(allocator);
    defer logger.deinit();

    // Enable JSON output with colors
    var config = logly.Config.default();
    config.json = true;
    config.pretty_json = true;
    config.color = true;  // Enable colors for JSON output
    logger.configure(config);

    // Bind context that will appear in all logs
    try logger.bind("app", .{ .string = "myapp" });
    try logger.bind("version", .{ .string = "1.0.0" });
    try logger.bind("environment", .{ .string = "production" });

    try logger.info("Application started", @src());
    try logger.success("All systems operational", @src());
    try logger.warn("Connection pool near capacity", @src());  // Short alias
    try logger.err("Database connection failed", @src());

    std.debug.print("\nJSON logging example completed!\n", .{});
}

JSON with Colors

JSON output now supports ANSI colors based on log level, just like console output:

• INFO - White text
• SUCCESS - Green text
• WARNING - Yellow text
• ERROR - Red text
• DEBUG - Blue text
• CRITICAL - Bright red text

To enable JSON colors:

var config = logly.Config.default();
config.json = true;
config.color = true;  // Enable colors for JSON
logger.configure(config);

Expected Output

With colors enabled, the entire JSON block will be colored based on the log level:

{
  "timestamp": "2024-01-15 10:30:45.+000",
  "level": "INFO",
  "message": "Application started",
  "app": "myapp",
  "version": "1.0.0",
  "environment": "production"
}

JSON File Output (Valid JSON Array)

When logging JSON to files, Logly automatically formats the output as a valid JSON array with proper comma separators:

// Add a JSON file sink
_ = try logger.addSink(.{
    .path = "logs/app.json",
    .json = true,
    .pretty_json = true,
});

try logger.info("First message");
try logger.warning("Second message");
try logger.err("Third message");

File output (logs/app.json):

[
{
  "timestamp": "2024-01-15 10:30:45.+000",
  "level": "INFO",
  "message": "First message"
},
{
  "timestamp": "2024-01-15 10:30:45.+001",
  "level": "WARNING",
  "message": "Second message"
},
{
  "timestamp": "2024-01-15 10:30:45.+002",
  "level": "ERROR",
  "message": "Third message"
}
]

This ensures the JSON file is always valid and can be parsed by any JSON parser.

Console vs File JSON

Feature	Console Output	File Output
Format	Individual JSON objects	JSON array [...]
Separators	Newline between objects	Comma , between objects
Colors	Supported (ANSI codes)	No colors (plain text)
Valid JSON	Each line is valid	Entire file is valid

Disable JSON Colors

To output plain JSON without ANSI codes (for file storage or log aggregation):

var config = logly.Config.default();
config.json = true;
config.color = false;  // No colors in JSON
logger.configure(config);

Custom Levels in JSON

Custom levels display their actual names and colors in JSON:

try logger.addCustomLevel("AUDIT", 35, "35");  // Magenta
try logger.custom("AUDIT", "User login event");

Output (colored in magenta):

{
  "timestamp": "2024-01-15 10:30:45.+000",
  "level": "AUDIT",
  "message": "User login event"
}