| 摘要 |
An internet user visits a web site and requests to see imagery from a specified one of a plurality of video cameras. At a system associated with the web site, a load distribution server assigns the user's request to one of a plurality of image servers. The assigned image server first checks its local image cache to see whether a recent image from the specified camera is stored there. If so, the image from that local image cache is sent to the user. If the local image cache does not have a recent image from the requested camera, the assigned image server then checks its local request cache to see whether an earlier process has recently requested the same imagery. If so, then the assigned image server simply waits for the earlier process to compete instead of initiating its own new image retrieval request. If no earlier process has recently requested the same imagery, the assigned image server issues its own image retrieval request. Information in image and the request caches of each image server is replicated across all the image servers.
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