Resolving the ruleno / ruleset confusion

[Loic Dachary <loic@dachary.org>]

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Hi,

As you noticed, there are places where ruleset and ruleno / ruleid are used interchangeably although they are not. This is a source of subtle bugs that can be hard to trace. By default ruleid and ruleset are the same, but dumping a crush map including

rule data {
        ruleset 0
        type replicated
        min_size 1
        max_size 10
        step take default
        step chooseleaf firstn 0 type host
        step emit
}
rule metadata {
        ruleset 1
        type replicated
        min_size 1
        max_size 10
        step take default
        step chooseleaf firstn 0 type host
        step emit
}

and swapping the rules as follows

rule metadata {
        ruleset 1
        type replicated
        min_size 1
        max_size 10
        step take default
        step chooseleaf firstn 0 type host
        step emit
}

rule data {
        ruleset 0
        type replicated
        min_size 1
        max_size 10
        step take default
        step chooseleaf firstn 0 type host
        step emit
}

will have ruleset 1 with rule id 0 and ruleset 0 with rule id 1

Since the ruleset is the only reliable number, from the user point of view, we could simply change CrushWrapper.h to never return the rule id and assume only ruleset are given in argument, even where it currently claims to be a rule id.

The downside is that looking up the ruleset implies iterating over all the rules, but that's probably not an issue.

What do you think ?

Cheers
-- 
Loïc Dachary, Artisan Logiciel Libre


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