Configuration

Environment variables

To configure QuantumLeap you can use the following environment variables:

Variable	Description
`CRATE_HOST`	CrateDB Host
`CRATE_PORT`	CrateDB Port
`DEFAULT_LIMIT`	Max number of rows a query can retrieve
`KEEP_RAW_ENTITY`	Whether to store original entity data
`POSTGRES_HOST`	PostgreSQL Host
`POSTGRES_PORT`	PostgreSQL Port
`POSTGRES_DB_NAME`	PostgreSQL default db
`POSTGRES_DB_USER`	PostgreSQL user
`POSTGRES_DB_PASS`	PostgreSQL password
`POSTGRES_USE_SSL`	`t` or `f` enable SSL
`REDIS_HOST`	Redis Host
`REDIS_PORT`	Redis Port
`USE_GEOCODING`	`True` or `False` enable or disable geocoding
`CACHE_GEOCODING`	`True` or `False` enable or disable caching for geocoding
`CACHE_QUERIES`	`True` or `False` enable or disable caching for queries
`DEFAULT_CACHE_TTL`	Time to live of metadata cache, default: 60 (seconds)
`QL_CONFIG`	Pathname for tenant configuration
`QL_DEFAULT_DB`	Default backend: `timescale` or `crate`
`CRATE_WAIT_ACTIVE_SHARDS`	Specifies the number of shard copies that need to be active for write operations to proceed. Default `1`. See related crate documentation.
`USE_FLASK`	`True` or `False` to use flask server (only for Dev) or gunicorn. Default to `False`
`LOGLEVEL`	Define the log level for all services (`DEBUG`, `INFO`, `WARNING` , `ERROR`)

NOTE * DEFAULT_LIMIT. This variable specifies the upper limit L of rows a query operation is allowed to fetch from the database and return to client. The actual number of rows will be the least of L and the client-specified limit or L if the client didn't specify a limit. If not set through this variable, L defaults to 10,000. This variable is read in on each API call to query endpoints so it can be set dynamically and it will affect every subsequent query operation. The variable string value you set should be convertible to an integer, if not, the default value of 10,000 will be used instead. * KEEP_RAW_ENTITY. If true, then each notified entity will be stored in its entirety as JSON in an additional column of the corresponding entity table. (This may result in the table needing up to 10x more storage.) If false, the JSON will only be stored (as detailed earlier) in case the conversion from JSON to tabular fails---typically this happens when the notified entity contains a previously notified attribute whose type is now different than it used to be in the past. This variable is read in on each API call to the notify endpoint so it can be set dynamically and it will affect every subsequent insert operation. Any of the following (case insensitive) values will be interpreted as true: 'true', 'yes', '1', 't', 'y'. Anything else counts for false, which is also the default value if the variable is not set.

Database selection per different tenant

QuantumLeap can use different time series databases to persist and query NGSI data. Currently both CrateDB and Timescale are supported as back ends, even though query functionality is not yet available for Timescale.

If no configuration is provided QuantumLeap assumes CrateDB is the back end to use and will store all incoming NGSI data in it. However, different back ends can be configured for specific tenants through a YAML configuration file. To use this feature, you have to set the environment variable below:

QL_CONFIG: absolute pathname of the QuantumLeap YAML configuration file. If not set, the default configuration will be used where only the Crate back end is available.

The YAML configuration file specifies what back end to use for which tenant as well as the default back end to use for any other tenant not explicitly mentioned in the file. Here's an example YAML configuration:

tenants:
    t1:
        backend: Timescale
    t2:
        backend: Crate
    t3:
        backend: Timescale

default-backend: Crate

With this configuration, any NGSI entity coming in for tenant t1 or t3 will be stored in Timescale whereas tenant t2 will use Crate. Any tenant other than t1, t2, or t3 gets the default Crate back end.