Thread-safe circular buffer in Java

Adam Matan picture Adam Matan · Jun 18, 2012 · Viewed 20.9k times · Source

Consider a few web server instances running in parallel. Each server holds a reference to a single shared "Status keeper", whose role is keeping the last N requests from all servers.

For example (N=3):

Server a: "Request id = ABCD"        Status keeper=["ABCD"]
Server b: "Request id = XYZZ"        Status keeper=["ABCD", "XYZZ"] 
Server c: "Request id = 1234"        Status keeper=["ABCD", "XYZZ", "1234"]
Server b: "Request id = FOO"         Status keeper=["XYZZ", "1234", "FOO"]
Server a: "Request id = BAR"         Status keeper=["1234", "FOO", "BAR"]

At any point in time, the "Status keeper" might be called from a monitoring application that reads these last N requests for an SLA report.

What's the best way to implement this producer-consumer scenario in Java, giving the web servers higher priority than the SLA report?

CircularFifoBuffer seems to be the appropriate data structure to hold the requests, but I'm not sure what's the optimal way to implement efficient concurrency.

Answer

MahdeTo picture MahdeTo · Jun 21, 2012
Buffer fifo = BufferUtils.synchronizedBuffer(new CircularFifoBuffer());