Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for providing a group membership discovery service. Join requests are received from clients, including a respective group and value pair. A respective count for each received pair is updated, the count indicating a count of a join events received by servers for the pair. Notification is sent to one or more other clients that have requested such notification, wherein the notification includes a first group and value pair having a respective count that was updated for a first time. A notification is received from a server regarding a different second group and value pair received by the server and a respective count for the second group and value pair is updated.

Abstract: The umbrella lamp assembly is adapted for mounting to an umbrella stem and includes a hollow body comprising first and second light transmitting shells. The shells are coupled together by an assembly which permits opening of the shells for placing the hollow body around an umbrella stem and which urges the shells toward each other. The shells have recesses at the top and bottom thereof for receiving and accommodating the umbrella stem in a frictional manner. A lamp is mounted in the hollow body and a mounting for receiving a battery is provided in the hollow body. A switch is mounted to one shell and is electrically coupled to the lamp and to a battery mounted in the hollow body.