Data Streams are records that represent sets of data streamed from sensors or other real-world devices.
Each Data Stream must have a type. All Asset types have a common set of attributes and relationships. Specific Data Stream types may also add additional attributes and relationships (collectively referred to as "fields"). Data Stream types are defined by modules, and are only available if their module is enabled. The modules included with farmOS define the following Data Stream types:
- Listener (Legacy)
Each Data Stream will be assigned two unique IDs in the database: a universally unique identifier (UUID), and an internal numeric ID.
The UUID will be unique across farmOS databases. The internal ID will only be unique to a single farmOS database. Therefore, the farmOS API uses UUIDs to ensure that IDs pulled from multiple farmOS databases do not conflict. Internally, farmOS modules use the internal IDs to perform CRUD operations.
Data Streams have a number of attributes that serve to describe their meta information. All Data Stream have the same standard set of attributes. Modules can add additional attributes.
Attributes that are common to all Data Stream types include:
- Private key
Data Streams must have a name that describes them. The name is used in lists of Data Streams to easily identify them at quick glance.
A Data Stream's private key is the password used to post data to (and get data from) its API endpoint.
A Data Stream may be marked as "public" to allow read-access from the API without a private key. This is useful for loading data into public third-party apps or scripts, for graphing or other purposes. Data Streams are not public by default.
Data Streams can be related to other records in farmOS These relationships are stored as reference fields on Data Stream records.
All Data Streams have the same standard set of relationships. Modules can add additional relationships.
Relationships that are common to all Data Streams types include:
Data Streams can reference one or more Assets to indicate that the data they collect is directly relevant to them.
For example, if a soil moisture sensor that is installed in a field can be represented with a Sensor Asset (for the soil moisture sensor device itself), with a Data Stream (soil moisture data readings), that reference a Land Asset (the field it is installed in). This makes it possible for a single device to be moved/reused for monitoring multiple Assets, by moving the Sensor Asset and creating new Data Streams.
In addition to the fields that are common to all Data Stream types described above, some types add additional type-specific fields. These include:
Basic Data Streams do not define any type-specific fields.
Listener (Legacy) Data Streams have an additional "public key" attribute, which is used in the Data Stream's API endpoint for posting/getting data. This was used in farmOS 1.x to provide a unique ID for the sensor, separate from the Sensor Asset ID that housed the data. This is no longer needed in farmOS 2.x, because each Data Stream has its own UUID, which is used in the API endpoints instead. The public key is retained for Legacy (Listener) Data Streams to ensure that existing sensors can continue to push data without needing to be reconfigured.