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Streaming ingestion policy

Streaming ingestion target scenarios

Applies to: ✅ Azure Data Explorer

Streaming ingestion should be used for the following scenarios:

• Latency of less than a few seconds is required.
• To optimize operational processing of many tables where the stream of data into each table is relatively small (a few records per second), but the overall data ingestion volume is high (thousands of records per second).

If the stream of data into each table is high (over 4 GB per hour), consider using queued ingestion.

• To learn how to implement this feature and about its limitations, see streaming ingestion.
• For information about streaming ingestion management commands, see Management commands used for managing the streaming ingestion policy.

Streaming ingestion policy definition

The streaming ingestion policy contains the following properties:

• IsEnabled:
  • defines the status of streaming ingestion functionality for the table/database
  • mandatory, no default value, must explicitly be set to true or false
• HintAllocatedRate:
  • if set provides a hint on the hourly volume of data in gigabytes expected for the table. This hint helps the system adjust the amount of resources that are allocated for a table in support of streaming ingestion.
  • default value null (unset)

To enable streaming ingestion on a table, define the streaming ingestion policy with IsEnabled set to true. This definition can be set on a table itself or on the database. Defining this policy at the database level applies the same settings to all existing and future tables in the database. If the streaming ingestion policy is set at both the table and database levels, the table level setting takes precedence. This setting means that streaming ingestion can be generally enabled for the database but specifically disabled for certain tables, or the other way around.

Note

If a table doesn't get streaming ingestion directly, but only via an update policy, no streaming ingestion policy has to be defined on this table.

Set the data rate hint

The streaming ingestion policy can provide a hint about the hourly volume of data expected for the table. This hint will help the system adjust the amount of resources allocated for this table in support of streaming ingestion. Set the hint if the rate of streaming data ingress into the table will exceed 1 Gb/hour. If setting HintAllocatedRate in the streaming ingestion policy for the database, set it by the table with the highest expected data rate. It isn't recommended to set the effective hint for a table to a value much higher than the expected peak hourly data rate. This setting may have an adverse effect on the query performance.