# Dataflow V1beta3 API - Module Google::Cloud::Dataflow::V1beta3::StreamingMode (v0.17.0)

0.17.0 (latest) 0.16.0 0.15.0 0.14.1 0.13.1 0.12.1 0.11.0 0.10.0 0.9.1 0.8.2 0.7.0 0.6.0 0.5.0 0.4.0 0.3.0 0.2.0 0.1.4 Reference documentation and code samples for the Dataflow V1beta3 API module Google::Cloud::Dataflow::V1beta3::StreamingMode.

Specifies the Streaming Engine message processing guarantees. Reduces cost
and latency but might result in duplicate messages written to storage.
Designed to run simple mapping streaming ETL jobs at the lowest cost.
For example, Change Data Capture (CDC) to BigQuery is a canonical use
case. For more information, see
[Set the pipeline streaming
mode](https://cloud.google.com/dataflow/docs/guides/streaming-modes).

## Constants

### STREAMING_MODE_UNSPECIFIED

**value:** 0  
Run in the default mode.

### STREAMING_MODE_EXACTLY_ONCE

**value:** 1  
In this mode, message deduplication is performed against persistent state
to make sure each message is processed and committed to storage exactly
once.

### STREAMING_MODE_AT_LEAST_ONCE

**value:** 2  
Message deduplication is not performed. Messages might be processed
multiple times, and the results are applied multiple times.
Note: Setting this value also enables Streaming Engine and
Streaming Engine resource-based billing.