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Many service applications use actors as a programming model for the middle tier, to simplify synchronization, fault-tolerance, and scalability. However, efficient operation of such actors in multiple, geographically distant datacenters is challenging, due to the very high communication latency. Caching and replication are essential to hide latency and exploit locality; but it is not a priori clear how to combine these techniques with the actor programming model.We present Geo, an open-source geo-distributed actor system that improves performance by caching actor states in one or more datacenters, yet guarantees the existence of a single latest version by virtue of a distributed cache coherence protocol. Geo's programming model supports both volatile and persistent actors, and supports updates with a choice of linearizable and eventual consistency. Our evaluation on several workloads shows substantial performance benefits, and confirms the advantage of supporting both replicated and single-instance coherence protocols as configuration choices. For example, replication can provide fast, always-available reads and updates globally, while batching of linearizable storage accesses at a single location can boost the throughput of an order processing workload by 7x.

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The modern medical community attaches great importance to contraception. The reasons for this are: 1) the desire to eliminate the wave of abortion, 2) the desire to enable women to decide the question of maternity themselves, 3) to teach contraception where eugenic and social indications prompt it, etc. At the first meeting of maternity protection workers, the following statement was made: the duty of motherhood, although still considered as a high duty, is not compulsory for women, even if this would be to the disadvantage of the state (Kaplun). Having taken this view, we must take a closer look at existing contraceptives, study them, and recommend those that are most advisable and harmless.