Log Format Standards — Defining Consistent Log Schemas Across Teams

// Standard log schema definition
const logSchemaDefinition = {
  $schema: 'https://json-schema.org/draft/2020-12/schema',
  type: 'object',
  required: ['timestamp', 'level', 'message', 'service'],
  properties: {
    timestamp: { type: 'string', format: 'date-time' },
    level: { type: 'string', enum: ['TRACE', 'DEBUG', 'INFO', 'WARN', 'ERROR', 'FATAL'] },
    message: { type: 'string', maxLength: 1000 },
    service: {
      type: 'object',
      properties: {
        name: { type: 'string' },
        version: { type: 'string' },
        environment: { type: 'string', enum: ['dev', 'staging', 'prod'] },
        host: { type: 'string' },
        instance: { type: 'string' }
      }
    },
    correlation: {
      type: 'object',
      properties: {
        id: { type: 'string', format: 'uuid' },
        traceId: { type: 'string' },
        spanId: { type: 'string' }
      }
    },
    user: {
      type: 'object',
      properties: {
        id: { type: 'string' },
        type: { type: 'string', enum: ['user', 'service', 'anonymous'] }
      }
    },
    request: {
      type: 'object',
      properties: {
        method: { type: 'string' },
        path: { type: 'string' },
        statusCode: { type: 'integer', minimum: 100, maximum: 599 },
        duration: { type: 'integer', minimum: 0 }
      }
    },
    error: {
      type: 'object',
      properties: {
        code: { type: 'string' },
        message: { type: 'string' },
        stack: { type: 'string' },
        fingerprint: { type: 'string' }
      }
    },
    context: { type: 'object' }
  }
};

// Schema validation middleware
function validateLogEntry(entry) {
  const ajv = new Ajv();
  const validate = ajv.compile(logSchemaDefinition);
  const valid = validate(entry);

  if (!valid) {
    console.error('Log entry failed schema validation:', validate.errors);
    return false;
  }
  return true;
}