Implementing gauge as a callback about go-metrics HOT 8 CLOSED

Does embedding metrics.Gauge in your own type and metrics.Registering that struct serve your purposes? The main reason the various metrics are interface types is to allow this so we don't have to register callbacks and such.

from go-metrics.

Yes that would work.
However, in Java even the counter had a set operation and it could be implemented in go-metrics as well. At which point a gauge would not be very different from a standard counter. The pull mechanic is useful as it means the user of the library does not have to think about how often the value changes or how to setup a periodic update. Not that that is very difficult in go. As you suggest this can be done using embedding would be nice to have that hidden in go-metrics rather than application code.

from go-metrics.

I'm sorry but I still don't understand what a callback-based API would buy us.

I often embed a metrics.Gauge and override the Value() method to do something non-standard and register the embedding struct with metrics.Register. Then the pulling you describe is handled by the reporter that's iterating over the registry every once-in-a-while.

from go-metrics.

I am just proposing that, what you describe should be the standard way of using a gauge. And the counter metric be extended to give the functionality currently supported by gauges. However, this is just a minor gripe at this point as I can embed externally to go-metrics.

from go-metrics.

By your last comment it sounds like you're actually asking for an arbitrarily-valued version of metrics.Counter.Clear()?

I'm 100% not interested in a callback-based API for individual metrics and, as you agreed yourself, intervals are so easy in Go that there's barely a reason for the various emitters to even think about them.

from go-metrics.

@rcrowley I am quite new to Go. If I put all my Gauges into a map. How would I manage to retrieve new values for the map periodically?

from go-metrics.

@jhiemer were you able to resolve your question? If you have all your Gauges in a map, you can do something like this (may not actually compile, but should get you most of the way):

timer := time.NewTicker(5 * time.Second)
for {
    <- timer
    for label, gauge := range mapOfGauges {
        // do something with gauge
    }
}

Closing this issue, as it no longer appears to be an issue.

from go-metrics.

@jhiemer You can also look at the implementation of various reporters, see log.go for example.

from go-metrics.