Object Metrics & Freshness

Object-level monitoring metrics and data freshness tracking

Object-level metrics collect information about tables and views as a whole — row counts, schema metadata, definition hashes, and data freshness.

monitor-chart-object

Object-Level Metrics

Key	Type	Description
metadata	bool	Collect schema information — column names, types, and table type. Enables schema change detection.
row_count	bool	Count the total number of rows via COUNT(*). Also used as a baseline for anomaly detection.
body_md5	bool	Track the MD5 hash of view or stored procedure definitions to detect code changes. Not applicable to regular tables.

objects:
  public.users:
    metadata: true
    row_count: true

  public.my_view:
    metadata: true
    body_md5: true

Alert on Change

Use alert_on_change to specify which types of changes should trigger alerts:

Change Type	Description
name	Object was renamed
type	Object type changed
timestamp	Last modified timestamp changed
size	Object size changed
body	View or procedure definition changed
count	Row count changed

objects:
  public.users:
    metadata: true
    row_count: true
    alert_on_change:
      - count
      - size
      - timestamp

Data Freshness

Freshness monitoring detects when data becomes stale. Combine freshness_column with freshness_threshold to track data age and receive alerts when tables fall behind their expected update schedule.

How It Works

When freshness_column is set, Sling queries MAX(freshness_column) to determine the timestamp of the most recent data. If the result is older than freshness_threshold, a data_stale event is fired.

If only freshness_threshold is set without freshness_column, Sling falls back to the object's metadata timestamp (last DDL or modification time). This is less precise for tables that receive INSERT operations without schema changes.

Duration Format

Thresholds use duration strings composed of one or more units:

Unit	Meaning	Example
d	Days	7d = 7 days
h	Hours	24h = 24 hours
m	Minutes	30m = 30 minutes
s	Seconds	60s = 60 seconds

Units can be combined: "1d12h" = 1 day and 12 hours, "1h30m" = 1 hour and 30 minutes.

Basic Freshness Check

objects:
  public.orders:
    freshness_column: created_at
    freshness_threshold: "12h"

  public.users:
    freshness_column: updated_at
    freshness_threshold: "24h"

Freshness in Defaults

Apply a default freshness configuration to all objects, then override per table as needed:

defaults:
  freshness_column: updated_at
  freshness_threshold: "24h"

objects:
  public.users: {}               # uses default (24h on updated_at)
  public.orders:
    freshness_column: created_at  # different column
    freshness_threshold: "6h"     # tighter SLA

For accurate freshness detection, set freshness_column to a timestamp column that is updated when new data arrives. Without it, Sling relies on metadata timestamps which may not reflect actual data changes.

Complete Example

connection: MY_POSTGRES

defaults:
  metadata: true
  row_count: true

objects:
  public.users:
    freshness_column: updated_at
    freshness_threshold: "24h"
    alert_on_change:
      - count
      - timestamp

  public.orders:
    freshness_column: created_at
    freshness_threshold: "6h"
    alert_on_change:
      - count

  public.products:
    row_count: true
    body_md5: false

  public.daily_report_view:
    metadata: true
    body_md5: true
    alert_on_change:
      - body