GeoWebCache currently supports multiple backend servers for the same layer. It is also possible to specify the number of simultaneous requests triggered by a seeding request, but requests from clients are generally unthrottled. Bursts of requests can lead overload the backend, resulting in suboptimal performance.
A simple solution for this problem is to define each WMS server as a separate resource in the configuration. Each one is associated with a dispatcher which queues requests, and only a set number of requests are allowed to run simultaneously.
A further extension of this concept would be to prioritize requests (not preempting) and place them on different queues accordingly. For instance, you could use the ip address of the client to prioritize a request, thus ensuring better service for paying customers or employees. Similarly, seeding requests could be prioritized lower, so that you can continue seeding without delaying clients noticably.
Funding
This roadmap item is currently unfunded.
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Other Roadmap Items
Right now a seeding process can easily overload a server, especially if it is in a live environment also responding to client requests. This could be improved in several ways to queue and prioritize requests so that the GeoWebCache seeder is smart enough to not overload the server.
Seeding is the process of pre-populating the cache with tiles. Currently a seed request can only take a bounding box. One improvement we could make is to let the seeder take a polygon, which can efficiently delimit the area of interest, saving significant time and bandwidth. Another improvement to be made is depth-first seeding, for cases when the center of the seed is of the most interest.
Funded: GeoWebCache does a great job caching static datasets and these improvements help make it a more active cache.