A feed is a real-time stream of data coming into ArcGIS Velocity. Feeds typically connect to external sources of observational data such as Internet of Things (IoT) platforms, message brokers, or third-party APIs. Feeds parse incoming tabular, point, polyline, or polygon data and expose it for analysis and visualization. A feed is also a type of stream layer and can be added to a map, allowing you to visualize information as soon as it is received.
The following feed types are available in Velocity:
- Web and Messaging:
- A transportation agency asset manager creates an Azure Event Hub feed to receive observational data from IoT sensors situated along a roadway.
- A GIS analyst creates a Feature Layer feed to ingest new features from a feature layer being edited by hundreds of users in a web application.
Polling and streaming feeds
There are two primary types of feeds in Velocity, polling feeds and streaming feeds.
A polling feed polls the specified source of data at a user-defined interval such as every 10 seconds or every minute. Examples of polling feeds include Feature Layer, HTTP Poller, and RSS. When a polling interval is set, the polling occurs on regular clock intervals as opposed to the start time of the feed. For example, if a feed is set to poll for data every 5 minutes, and the feed is started at 8:03am, the first request for data will occur at 8:05am, the next at 8:10am, and so on.
A streaming feed connects to the specified source of streaming data and remains connected. Any time the source sends additional data, the streaming feed immediately receives and processes the data into events. Examples of streaming feeds include Stream Layer, MQTT, and Kafka.
Starting and stopping a feed
A feed can be in either a started (running) or stopped state. A feed will only receive or poll its source of data when it is in a started state. When you create a feed, it will start automatically.
You can optionally choose to stop a feed if you want to discontinue ingesting features. If you edit a started feed, once the edits are saved the feed will restart.
Create a feed
To create a new feed, follow the steps below:
- Open the Velocity application.
- Click Create Feed to create a new feed.
- Choose the feed type you want to create by browsing the groups of feeds or by searching using a keyword. Feed types are grouped into several categories:
- Web and Messaging
- Select the feed type you want to create.
- Enter the feed configuration details. Note that, the configuration parameters will vary depending upon the feed type selected.
- Click Next to continue with the remaining steps including confirming the schema, identifying the key fields, and defining the polling interval (if applicable), and saving the feed.
Edit a feed
An existing feed can be edited. allowing you to update connection properties, schema configuration, key fields, and polling settings. After editing a feed, if the feed was running it will be restarted so the changes will take effect immediately.
Two options exist for editing a feed in the Velocity application:
- On the Feeds list page, click the pencil icon associated with the feed you want to edit.
- On the Feeds details page, click Edit to edit the feed.