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2010-06-04Merge branch 'uw/mnesia-overload' into devErlang/OTP
* uw/mnesia-overload: Enable continuous monitoring of mnesia overload status
2010-05-09Enable continuous monitoring of mnesia overload statusUlf Wiger
Mnesia currently issues an event whenever it detects an overload condition. It recognizes two different types of overload: - whenever the message queue of mnesia_tm process grows large - when a log dump interval triggers before the previous dump is done These events could be used to trigger a load regulation mechanism to reduce the load until the condition seizes. The missing piece is that there is no facility to ask mnesia whether the overload condition still exists. This patch implements a couple of functions in mnesia_lib that can be used to sample the overload status. It has been tested in a load regulator component being developed by Erlang Solutions. No mnesia test suites have been run, since they are not available. No documentation has been updated. The functions in mnesia_lib are at any rate undocumented (as are all other functions in that module). A decision would have to be made about whether to provide a documented API on top of these functions. The internal state record of mnesia_recover has been modified. For this reason, a code change hook has been provided.
2009-11-20The R13B03 release.OTP_R13B03Erlang/OTP