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A Multi-site coordination (MUSIC) service in which ONAP components can maintain and access geo-distributed state. MUSIC maintains state in a highly scalable key-value store (Cassandra) but also provides a locking service (built on Zookeeper) on top of it through which the ONAP components can obtain stronger consistency on the shared state. MUSIC exports a REST API that can be used by the ONAP components.
A multi-site DB cache (mdbc) that allows ONAP components that maintain state in a database to avail the benefits of MUSIC without changing their SQL DB code. While some ONAP components may want to use MUSIC directly to maintain state, others may already maintain state in a SQL database. For such db-based ONAP components, within a site, these ONAP components can rely on existing db clustering techniques like MariaDB clustering. mdbc will intercept each of these read/write calls to the db and mirror this state to other geo-distributed sites through MUSIC. mdbc is implemented as a jdbc driver and ONAP components can simply replace their existing jdbc driver with the mdbc driver to avail its benefits of geo-redundancy.
Configurable high-availability (HAL) recipes for distributed failure-detection, failover, leader-election, and request re-distribution. HAL is expected to run as a companion daemon (for e.g. a process within the same container) to each ONAP components replica on each site in a geo-distributed set-up. The HAL daemons across the sites, working together can perform several functions: (i) detect failures in their companion ONAP component replicas and attempt to bring them back (ii) detect failures in other HAL daemons (iii) perform leader-election and failover in case of replica or entire -site failures. (iv) redistribute requests of the failed ONAP component replica to other replicas through a policy-driven optimization framework. Internally, HAL uses MUSIC to maintain its own state. HAL exports a REST API and the ONAP components can simply configure HAL according to their own needs by providing keep-alive scripts and request re-routing policies.
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