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 0.6.0.

A quick example for diehard usage.

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}
  (fetch-data-from-the-moon))

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

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

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

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

A rate limiter protects your code block to run limited times per second. It will block or throw exception depends on your configuration. (:rate is a floating point number, and can be less than 1.0. Example: 0.5 is once every two seconds.)

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

(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
(dh/defbulkhead my-bh {:concurrency 10})

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

Timeouts allow you to fail an execution with TimeoutExceededException if it takes too long to complete

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

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

(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"})))

output:

"failed attempt"
"retrying..."
"failed attempt"
"retrying..."
"failed attempt"
"retrying..."
"failed attempt"
"failed..."
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.

This project uses deps.edn and build.edn for dependency management. To build the project, run

clojure -T:build install

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

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