Riemann: longs and doubles

In the just-released riemann-java-client 0.0.6, riemann-clojure-client 0.0.6, riemann-ruby-client 0.0.8, and the upcoming riemann 0.1.4 (presently in master), Riemann will support two new types of metrics for events.


# signed 64-bit integers (variable-width-encoded) optional sint64 metric_sint64 = 13; # double-precision IEEE 754 floats optional double metric_d = 14;

Events still have only a single logical metric; this change simply allows the protocol to represent a broader range of numbers. Clients should prefer metric_sint64 for all integer values from -263 to 263 - 1, and prefer metric_d for double-precision floats. Clients should also write metric_f wherever possible and fall back to reading metric_f, for compatibility with older versions of Riemann.

Here's how the Ruby client does it. Note that Ruby's Float is actually a double.

def metric metric_d || metric_sint64 || metric_f end def metric=(m) if Integer === m and (-(2**63)...2**63) === m # Long self.metric_sint64 = m self.metric_f = m.to_f else self.metric_d = m.to_f self.metric_f = m.to_f end end

Javascript has only one numeric type: double-precision IEE754 floats (sort of). Riemann uses Cheshire and will emit JSON numbers which may exceed the scale or resolution of a JS VM, e.g.:


… which in V8 will be parsed as the number 12345678901234567000. Larger values may become +/- Infinity when parsed. Rationals are serialized as decimals.

Since most JS clients are engaged in visualization, loss of precision seems preferable to emitting JSON strings (e.g. 123 -> “123”) and forcing clients to use arbitrary-precision bignum libraries with custom operators. I'd like your feedback. :)

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