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Clojure library of flexible retry, circuit breaker and rate limiter

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Clojure library to provide safety guard to your application. Some of the functionality is wrapper over Failsafe.

Note that from 0.7 diehard uses Clojure 1.9 and spec.alpha for configuration validation. Clojure 1.8 users could stick with diehard



A quick example for diehard usage.

Retry block

A retry block will re-execute inner forms when retry criteria matches.

(require '[diehard.core :as dh])
(dh/with-retry {:retry-on TimeoutException
                :max-retries 3}

Circuit breaker

A circuit breaker will track the execution of inner block and skip execution if the open condition triggered.

(require '[diehard.core :as dh])

(defcircuitbreaker my-cb {:failure-threshold-ratio [8 10] :delay-ms 1000})

(dh/with-circuit-breaker my-cb (fetch-data-from-the-moon))

Rate limiter

A rate limiter protects your code block to run limited times per second. It will block or throw exception depends on your configuration.

(require '[diehard.core :as dh])

(defratelimiter my-rl {:rate 100})

(dh/with-rate-limiter my-rl (send-people-to-the-moon))


Bulkhead allows you to limit concurrent execution on a code block.

(require '[diehard.core :as dh])

;; at most 10 threads can run the code block concurrently (defbulkhead my-bh {:concurrency 10})

(dh/with-bulkhead my-bh (send-people-to-the-moon))


Timeouts allow you to fail an execution with

if it takes too long to complete
(require '[diehard.core :as dh])

(with-timeout {:timeout-ms 5000} (fly-me-to-the-moon))


Retry block

(dh/with-retry {:retry-on          Exception
                :max-retries       3
                :on-retry          (fn [val ex] (prn "retrying..."))
                :on-failure        (fn [_ _] (prn "failed..."))
                :on-failed-attempt (fn [_ _] (prn "failed attempt"))
                :on-success        (fn [_] (prn "did it! success!"))}
               (throw (ex-info "not good" {:not "good"})))


"failed attempt"
"failed attempt"
"failed attempt"
"failed attempt"
Execution error (ExceptionInfo) at main.user$eval27430$reify__27441/get (form-init6791465293873302710.clj:7).
not good


More options can be found in the documentation from cljdoc.


Copyright © 2016-2019 Ning Sun

Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.


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