使用Riemann在clojure中转换浮点字符串

Question

I am processing streams in Riemann and all the fields are strings. However I'd like to perform some numeric comparisons on some fields. Therefore I tried to convert them in float.

Let's say my stream is like that :

#riemann.codec.Event{:host "myHost", :service nil, :state nil, :description "my description", :pred_score "0.156"}

I've tried to modify the riemann.conf file with something like this :

(streams
 (with :new_field (read-string :pred_score))
 prn)

However I got some error and I feel like this is not the correct way to do this. I have recently read some stuffs making me think that I should use smap or adjust but I'm not sure.

I am absolutely not familiar with clojure by the way. (In fact I discovered it with riemann).

Have you got any idea on how to tackle the problem ?

Thanks in advance,

Robin.

Answer 1

I don't know about the riemann part, but in plain clojure you could use either Java interop or the Tupelo library . Using Java interop, you'd do:

> (def x {:host "myHost", :service nil, :state nil, :description "my description", :pred_score "0.156"} )
> (Double/parseDouble (:pred_score x))
0.156

The 'tupelo.parse' namespace wraps this inside a normal clojure function, and adds the ability to specify a default value to return in the event of a malformed value (instead of throwing an exception):

> (require '[tupelo.parse :as parse])
> (parse/parse-double (:pred_score x))
0.156
> (parse/parse-double "123.4x6" :default 0)
0