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MUSIC also provides a rich set of recipes (mdbc, prom, musicCAS, musicQ) that ONAP components can use to build multi-site active-active state-management solutions:
mdbc: The most crucial recipe is a multi-site database cache (mdbc) that enable ONAP components that maintain state in a SQLdatabase to avail the benefits of MUSIC without compromising their need to use transactional SQL DBs. These ONAP components can rely on existing db clustering techniques like MariaDB for transactionality and complex querying within a site. mdbc will intercept each of these read/write calls to the db cluster and mirror this state to other geo-distributed sites through MUSIC either synchronously or asynchronously (configurable at a table-level). For example, components like the ONAP Service Orchestrator that use MariaDB to maintain state can directly use this recipe with no change to their SQL code.
prom: MUSIC provides a recipe for policy-driven ownership management (prom) of state for ONAP components to (1) partition state across replicas during both initial placement and during failures based on their individual policies (2) ensure correct transfer of state ownership across replicas during site failures and network partitions (3) ensure that the new owner has access to the most recent version of state (if needed).
musicCAS: The distributed compare and set is a powerful primitive that will allow ONAP components to update shared state in an atomic manner. This is currently being used by the ONAP HAS (homing service) that is structured a job scheduler with multiple workers trying to pick up client-submitted jobs, while ensuring that only one of them actually performs the job.
musicQ: Implementing a geo-distributed queue is a hard problem with many performance implications when data belonging to a queue is sharded across nodes. MUSIC provides a queue API that carefully structures the data to ensure good performance. ONAP HAS (mentioned above) uses this as its job queue.
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