Metadata

The metadata field is where Astralog provides schema-less flexibility. It allows you to attach any custom context to your events without needing to run database migrations or define indexes beforehand.

• Dynamic Extraction: Astralog natively uses ClickHouse JSON functions to query these nested fields at lightning speed.
• High Cardinality: You can safely event fields with infinite unique values (like ip_address or session_id) inside the metadata without suffering the “high cardinality explosion” that crashes systems like Prometheus.

Best Practice: Static Messages

Always keep your root message static and move variable data into the metadata object. This makes aggregations much faster and cleaner.

❌ Bad Pattern (High Cardinality Message):

{
  "message": "User 123 failed to login from IP 192.168.1.1"
}

✅ Good Pattern (Static Message + Metadata):

{
  "message": "User login failed",
  "metadata": {
    "user_id": "123",
    "ip": "192.168.1.1"
  }
}