Monitors

Monitor your data for schema changes, freshness, anomalies, and column-level statistics

Monitors in Sling observe your data assets without moving data. They track schema drift, data freshness, row counts, column-level statistics, and anomalies — giving you continuous visibility into the health and quality of your database tables and views.

monitor-charts

What Can Monitors Do?

• Schema change detection — Track when tables, columns, or types are added, dropped, or altered

• Data freshness — Alert when data falls behind its expected update schedule

• Row count tracking — Monitor table sizes and detect unexpected growth or shrinkage

• Column statistics — Collect min/max/mean, percentiles, null counts, cardinality, and more

• Value validation — Enforce regex patterns, accepted values, and rejected values on columns

• Anomaly detection — Automatically detect spikes, drops, and pattern changes using z-score analysis

Quick Start

Create a YAML file that specifies which connection to monitor and what to track:

connection: MY_POSTGRES

defaults:
  metadata: true
  row_count: true

objects:
  # monitor all objects in schemas
  marketing.*:
  salesforce.*:

  public.users:
    freshness_column: updated_at
    freshness_threshold: "24h"
    columns:
      email:
        count_distinct: true

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

On the Sling Platform, save this file in the monitors/ directory of your project and schedule it as a job.

Monitors are a Sling Platform feature available on the Advanced plan. See Pricing for details.

Configuration Overview

A monitor configuration has five top-level keys:

Key	Required	Description
connection	Yes	The connection to monitor (must match a connection in env.yaml)
defaults	No	Default settings applied to all objects. See Structure.
objects	Yes	Map of object names or patterns to their monitoring configuration. See Structure.
schemata	No	Schema change detection settings. See Schema Changes.

For the complete YAML reference, see Structure.

Running Monitors

Monitor files are stored in the monitors/ directory of your project on the Sling Platform. Once created, you can schedule them as jobs with a cron expression for automated execution. Monitor runs process objects in parallel (default 2 threads) and retry transient errors up to 3 times.

Supported Connections

Databases

Database	Table Size	Percentiles	Freshness
PostgreSQL	Yes	Yes	Yes
MySQL / MariaDB	Yes	—	Yes
Snowflake	Yes	Yes	Yes
BigQuery	Yes	Yes (approx)	Yes
ClickHouse	Yes	Yes	Yes
DuckDB	Yes	Yes	Yes
SQL Server	Yes	Yes	Yes
Oracle	Yes	Yes	Yes
Redshift	Yes	Yes	Yes
Databricks	Yes	Yes	Yes
Trino / Athena	Yes	Yes	Yes
SQLite / D1	—	—	Yes

Notifications

Notification settings are a Sling Platform feature, configured per monitor job.

monitor-notification

Each monitor job supports four notification triggers:

Setting	Fires When
On Schema Change	Tables, columns, or types are added, dropped, or altered
On Freshness	Data exceeds its freshness threshold
On Anomaly	Metric values deviate significantly from historical baseline
On Failure	Monitor execution fails

Notifications can be sent via email, Slack, Discord, or Microsoft Teams.

Learn More

Detailed documentation for each aspect of monitors:

• Structure — Complete YAML reference, wildcards, defaults, and definition order

• Object Metrics & Freshness — Object-level metrics and data staleness detection

• Column Metrics & Validation — Column statistics and value validation rules

• Anomaly Detection — Z-score analysis, configuration, and event types

• Schema Changes — Schema drift detection and change events