joelittlejohn / clj-http-hystrix Goto Github PK

We use prometheus together with prometheus-hystrix in order to gather data for our Grafana dashboards and to trigger alarms in case something weird happens. Lately we also added some alarm triggers for our clojure projects that use clj-http-hystrix underneath.

As we use standard REST calls, HTTP status codes like 404 appear quite regularly. We noticed though that our clojure services (in opposite to the java services) trigger certain hystrix events ("bad_request" and "exception_thrown") that caused our Grafana dashboards to look quite bad:

I figured out that these Hystrix events are triggered due to HystrixBadRequestExceptions that are thrown here in case http/client-error? returns false. I believe this is a wrong behaviour though, as the javdoc states:

NOTE: This should only be used when an error is due to user input such as IllegalArgumentException otherwise it defeats the purpose of fault-tolerance and fallback behavior.

Also there is a test in the hystrix' core library that indicates that this exception should be used for different purposes.

Add support for user-defined defaults. This would let users, for example, set a default timeout that will be the fallback if the value is not supplied, making global configuration much easier.

The defaults could be an optional argument when adding the hook:

;; specify different defaults for threads and timeout, via optional argument to add-hook
(clj-http-hystrix.core/add-hook {:hystrix/threads 8
                                 :hystrix/timeout-ms 2500})

(clj-http/get "example.com" {:hystrix/command-key "example"})
;;=> {:hystrix/command-key "example"
;;    :hystrix/threads 8
;;    :hystrix/timeout-ms 2500
;;    ... rest are clj-http-hystrix defaults... }

;; or instead, use clj-http-hytrix defaults (unchanged)
(clj-http-hystrix.core/add-hook)

@joelittlejohn I'm happy to tackle this if you think its a reasonable feature to add.