Database technology - FoundationDB

Genesis provides two database solutions built on FoundationDB.

FDB and FDB2 are equivalent in terms of configuration, but they store data using a different data model.

• FDB uses a separate key-value for each table column.
• FDB2 stores all data in a single key-value.

Each mode has implications in terms of database limitations, as FDB can only store a maximum of 10MB data per transaction and 1MB data per key-value.

Therefore, for applications using small table records, FDB2 is more efficient. For applications using large table records, FDB is more efficient.

System definitions

For FDB and FDB2 layers, there are additional system definition items that you can apply in the genesis-system-definitions.kts file:

Setting	Description
FdbClusterFile	A path to an fdb.cluster file. If this item is not defined, the default fdb.cluster file will be used. This file is located in /etc/foundationdb/fdb.cluster
DbNamespace	A name for the internal FDB directory to use.
DbThreadsMin	The minimum number of threads to be created in the FDB layer thread pool. Defaults to the minimum of 4 or the number of processing units
DbThreadsMax	The maximum number of threads to be created in the FDB layer thread pool. Defaults to the maximum of 4 or the number of processing units multiplied by 2
DbThreadKeepAliveSeconds	Sets how many seconds a thread created over the DbThreadsMin value can live. If a thread is idle for a total of DbThreadKeepAliveSeconds and it was created as an additional thread (i.e. outside the DbThreadsMin threshold), it will be destroyed. Defaults to 5 minutes
DbOptimisticConcurrencyMode	Set the Optimistic Concurrency mode. Available values: STRICT, LAX and NONE. Defaults to NONE.

Sample configurations

Min and max thread count

systemDefinition {
    global {
        ...
        item(name = "DbThreadsMin", value = "5")
        item(name = "DbThreadsMax", value = "15")
        ...
    }
    ...
}

Thread timeouts to two minutes

systemDefinition {
    global {
        ...
        item(name = "DbThreadKeepAliveSeconds", value = "120")
        ...
    }
    ...
}

Cluster file location on windows

systemDefinition {
    global {
        ...
        item(name = "FdbClusterFile", value = "C:\\Genesis\fdb\fdb.cluster")
        ...
    }
    ...
}