The Feature Layer (existing) output in ArcGIS Velocity allows you to write output features to an existing Velocity layer, an existing ArcGIS Online hosted feature layer, or an existing ArcGIS Server feature layer. When using this output type, features are written to an existing feature layer, as opposed to creating a feature layer. The existing feature layer should be the same geometry type as the incoming data and contain all of the same attributes and field tags.
Examples
The following are example uses of the Feature Layer (existing) output:
- After ingesting real-time features from IoT sensors through a feed and a real-time analytic, an asset manager wants to add those observations to an existing feature layer.
- A GIS analyst performs analysis of the latest information in a big data analytic and appends the results to an existing layer that is already in use in various applications.
- A business analyst ingests a set of existing, historical observations from an external cloud store and configures a real-time analytic to process events as they occur and captures the new observations in an existing feature layer.
Usage notes
Keep the following in mind when working with the Feature Layer (existing) output:
- The selected feature layer must be hosted by Velocity, be an ArcGIS Online hosted feature layer, or an ArcGIS Server feature layer.
- The schema of the incoming data and the destination feature layer must generally match. Each should have the same geometry type and spatial reference, and the fields present in the incoming data should exist in the destination feature layer. Differences can include the following:
- The destination feature layer can have additional fields not present in the incoming data that can be used for data enrichment.
- The Map Fields tool can be used to transform the schema of the incoming data in an analytic workflow to align with the schema of the output feature layer.
- ArcGIS Server feature layers must be referenced in an ArcGIS Online portal item ID. To do this, go to your ArcGIS Online content page, and add an item referencing the layer by URL. If applicable, store credentials with this ArcGIS Online item. The Velocity feature layer existing output can then be configured to point to this ArcGIS Online portal item ID, which points to the ArcGIS Server feature layer URL.
- For Velocity layers, a data retention policy is required for all output feature layers because data grows over time. When writing to an existing feature layer and using the Add all new features option in the Data storage method parameter, the selected feature layer must have a data retention policy configured.
- When editor tracking is enabled and the Data storage method parameter is set to Add all new features, the editor name, date, and time are always the same. If the Data storage method parameter is set to Keep only latest feature for each Track ID value, a track observation that is updated has the editor name, date, and time updated after the first observation.
Parameters
The following are the parameters for the Feature Layer (existing) output:
| Parameter | Description | Data type |
|---|---|---|
Feature Service Portal Item ID | The portal item ID of the corresponding feature layer item created in ArcGIS Online. The feature layer must belong to the user creating the analytic. | String |
Data storage method | Data stored in a spatiotemporal feature layer supports high-velocity ingestion, high-volume storage over time, dynamic aggregation, and automated data retention if checked (true). This is the default.
| Boolean |
Creator or editor username | Specifies the creator or editor username for processed data. The username can be derived from a field of the incoming data or set as the analytic owner. The Creator and editor username parameter only applies and is shown when the existing feature layer already has editor tracking enabled. | String |
Considerations and limitations
The following are considerations and limitations when using the Feature Layer (existing) output:
- The selected feature layer must be hosted by Velocity, be an ArcGIS Online hosted feature layer, or an ArcGIS Server feature layer.
- Restrictions exist on the number of records written to ArcGIS Online hosted feature layer outputs using the Feature layer (existing) output, including the following:
- Real-time analytic output—When writing to an ArcGIS Online existing hosted feature layer from Velocity real-time analytics, no more than 120 events per minute can be written.
- Runs once big data analytic output—Up to 50,000 records can be written to an ArcGIS Online existing hosted feature layer output. The hosted feature layer must support the append function when writing from a runs once big data analytic.
- Scheduled/recurring big data analytic output—The number of records that can be written to an ArcGIS Online hosted feature layer output depends on the run frequency of the analytic. For each minute between each run, 120 records can be written per minute. For example, an analytic that runs every minute can write 120 output features per run, an analytic that runs every 5 minutes can write 600 output features per run, and an analytic that runs every 30 minutes can write 3,600 output features per run.
- ArcGIS Online organizations that have the premium data store can write at a higher rate depending on the premium data store plan.