bulwark exposes a macro called with-hystrix, that takes a map of Hystrix configuration and executes the body
in a Hystrix command.
(let [fallback (fn [_]
"failure")]
;; Returns "success"
(bulwark/with-hystrix {;; These three keys identify the Hystrix command
;; The group key is used to group commands together,
;; for reporting/monitoring. We suggest having a
;; single group key for all commands in your app.
:group-key "your-app"
;; The command key uniquely identifies the Hystrix command.
:command-key "foo-command"
;; The thread pool key identifies the thread pool
;; to be used to execute your Hystrix command.
;; If two commands have the same thread pool key,
;; they will share the same thread pool.
;; We suggest using different thread pools for each command.
:thread-pool-key "foo-thread-pool"
:thread-count 2
:breaker-sleep-window-ms 500
:breaker-error-threshold-percentage 20
:execution-timeout-ms 100
:fallback-fn fallback}
"success"))
(let [fallback
;; These are the keys the fallback function is passed.
(fn [{:keys [response-timed-out?
failed-execution-exception ; If an exception was thrown, it is available here
circuit-breaker-open?
semaphore-rejected? ; See https://github.com/Netflix/Hystrix/wiki/Configuration#execution.isolation.semaphore.maxConcurrentRequests
thread-pool-rejected?
]}]
"failure")]
;; Runs the fallback (because of a timeout) and evaluates to its return value, i.e. "failure"
(bulwark/with-hystrix {:group-key "your-app"
:command-key "foo-command"
:thread-pool-key "foo-thread-pool"
:thread-count 2
:breaker-sleep-window-ms 500
:breaker-error-threshold-percentage 20
:execution-timeout-ms 100
:fallback-fn fallback}
(Thread/sleep 500)
"success"))