US Patent 11108758 Reactive programming subscription context

Methods, systems, and apparatus, including computer programs encoded on computer storage media, for implementing subscription contexts in a reactive programming system. One of the methods includes receiving, by a reactive programming system comprising one or more computers, a reactive programming program defining an ordering of a plurality of operators, the plurality of operators including a subscriber context operator that writes a value to a subscription context for a particular subscriber, wherein the ordering defines an upstream subscription flow ordering from the particular subscriber to a publisher and a downstream data flow ordering from the publisher to the particular subscriber. The operators are evaluated in the upstream subscription flow ordering, including updating a subscription context of each operator with the value written by the subscriber context operator.