call_out_summand

[dworkin]

A new kfun, call_out_summand has been added to DGD and Hydra.

    int call_out_summand(string function, mixed delay, float summand, mixed args...)

call_out_summand works like call_out, but the summand argument, which will be passed to the function called, has to be a float. Any followup to call_out_summand which occur in the same object while the first one is still pending, will not start a new callout but will add to the pending callout's summand argument.

    call_out_summand("foo", 3, 1.0);
    call_out_summand("foo", 3, 2.0);
    /* foo(3.0) will be called */

For followup callouts, only the summand argument is relevant. All other arguments will be ignored.

The cloud library uses this to keep track of tick resource usage. Previously, this would basically double the amount of callouts run, because each ordinary callout would also start a resource update callout. With call_out_summand, the number of such resource update callouts can be reduced.