Logging

Logging — structured JSON logs, korelasi trace, dan integrasi observability.

Format Log

Semua log dalam format JSON struktural:

{
  "timestamp": "2024-01-15T10:30:00.123Z",
  "level": "Information",
  "message": "Order placed successfully",
  "trace_id": "abc123def456",
  "span_id": "xyz789",
  "user_id": "usr-123",
  "account_id": "acc-456",
  "order_id": "ord-789",
  "symbol": "EURUSD",
  "properties": {
    "order_type": "market",
    "lots": 0.5,
    "price": 1.0850
  }
}

Log Levels

Level	Penggunaan
Trace	Detail sangat granular (development only)
Debug	Informasi debugging
Information	Events normal (request received, order filled)
Warning	Event tidak biasa tapi tidak error
Error	Error yang butuh perhatian
Critical	Kegagalan sistem

Source-Generated Logging

Menggunakan source-generated log messages (tidak ILogger.Log langsung):

[LoggerMessage(Level = LogLevel.Information, Message = "Order {OrderId} placed for {Symbol}")]
public static partial void LogOrderPlaced(this ILogger logger, string orderId, string symbol);

// Usage
_logger.LogOrderPlaced(orderId, symbol);

Ini menghasilkan log yang di-optimasi dengan compile-time checks.

Structured Logging

Dengan Message Templates

_logger.LogInformation(
    "Order {OrderId} for {Symbol} filled at {Price} with {Pnl} P&L",
    orderId, symbol, fillPrice, pnl);

Dengan Objects

_logger.LogInformation(
    "Order completed: {OrderSummary}",
    new { orderId, symbol, fillPrice, pnl });

Trace Correlation

Automatic Propagation

trace_id dan span_id di-propagate otomatis:

// Child span
using var span = _tracer.StartActiveSpan("ProcessOrder");
span.SetAttribute("order_id", orderId);

// Log otomatis termasuk span context
_logger.LogInformation("Processing order {OrderId}", orderId);
// Output: { "trace_id": "abc123", "span_id": "child123", "order_id": "ord-456" }

Manual Correlation

// Correlate manual operation
var correlationId = Activity.Current?.TraceId.ToString() ?? Guid.NewGuid().ToString();
using (_logger.BeginScope(new Dictionary<string, object> { ["correlation_id"] = correlationId }))
{
    _logger.LogInformation("Starting correlated operation");
}

Log Sinks

Console (Development)

{
  "Logging": {
    "Console": {
      "FormatterName": "json"
    }
  }
}

File (JSON, rotation harian)

{
  "Logging": {
    "File": {
      "Path": "/logs/cmind-{Date}.json",
      "RollingInterval": "Day",
      "RetainedFileCountLimit": 30
    }
  }
}

CloudWatch (AWS)

{
  "Logging": {
    "CloudWatch": {
      "LogGroup": "/aws/cmind/app",
      "StreamName": "{InstanceId}",
      "BatchSize": 100,
      "Period": "00:00:05"
    }
  }
}

X-Ray / ADOT

Traces otomatis di-export via ADOT sidecar:

{
  "OTEL_EXPORTER_OTLP_ENDPOINT": "http://localhost:4317"
}

Query Logs

Dengan Serilog

// Di code
Log.Information("User {UserId} placed order {OrderId}", userId, orderId);

// Di query (Elasticsearch/kibana)
message: "placed order" AND userId: "usr-123"

Common Queries

# Find all errors for user
level:Error AND user_id: "usr-123"

# Find order-related logs
message: "*order*" AND trace_id: "abc123"

# Find slow requests
elapsed_ms: >5000

# Find all logs in trace
trace_id: "abc123" | sort timestamp ASC

Log Retention

Environment	Retention	Storage
Development	7 days	Local file
Staging	30 days	S3
Production	90 days	CloudWatch/S3

Best Practices

1. No sensitive data — jangan log password, token, PII.
2. Use correct level — Information untuk events normal, bukan Debug.
3. Structured always — selalu gunakan message templates, bukan string concatenation.
4. Include context — trace_id, user_id, account_id di setiap log.
5. Meaningful messages — "Order placed" bukan "Order processed".