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Merge pull request #9 from mtkp/custom-defaults
Custom defaults
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‎README.md‎

Lines changed: 16 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -24,9 +24,23 @@ Whenever you make an http request, add one or more of the hystrix-clj options to
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:hystrix/breaker-request-volume 20
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:hystrix/breaker-error-percent 50
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:hystrix/breaker-sleep-window-ms 5000
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:hystrix/bad-request-pred client-error?}}
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:hystrix/bad-request-pred client-error?})
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```
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Requests without any `:hystrix/...` keys won't use Hystrix. Any values not supplied will be set to their default values as above. Custom default values can also be specified when registering with `add-hook`:
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```clj
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(clj-http-hystrix.core/add-hook {:hystrix/timeout-ms 2500
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:hystrix/queue-size 12})
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;; now each request will fallback to these if not supplied
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(http/get "http://www.google.com" {:hystrix/command-key :google})
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;;=> {:hystrix/command-key :google
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;; :hystrix/timeout-ms 2500
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;; :hystrix/queue-size 12
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;; ... (rest are clj-http-hystrix defaults)
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;; }
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```
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Any values not supplied will be set to their default values as above. Requests with no Hystrix-related keys won't use Hystrix.
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## Bad requests
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‎src/clj_http_hystrix/core.clj‎

Lines changed: 94 additions & 63 deletions
Original file line numberDiff line numberDiff line change
@@ -13,23 +13,17 @@
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[com.netflix.hystrix.exception HystrixBadRequestException]
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[org.slf4j MDC]))
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16-
(def ^:private ^:const hystrix-keys
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#{:hystrix/fallback-fn
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:hystrix/group-key
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:hystrix/command-key
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:hystrix/threads
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:hystrix/queue-size
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:hystrix/timeout-ms
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:hystrix/breaker-request-volume
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:hystrix/breaker-error-percent
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:hystrix/breaker-sleep-window-ms
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:hystrix/bad-request-pred})
27-
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(defn default-fallback [req resp]
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(if (:status resp)
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resp
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{:status 503}))
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21+
(defn client-error?
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"Returns true when the response has one of the 4xx family of status
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codes"
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[req resp]
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(http/client-error? resp))
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(defn ^:private handle-exception
3428
[f req]
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(let [^Exception raw-response (try (f) (catch Exception e e))
@@ -40,6 +34,24 @@
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((http/wrap-exceptions (constantly resp)) req))
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resp))
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(def ^:private ^:const hystrix-base-configuration
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{:hystrix/command-key :default
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:hystrix/fallback-fn default-fallback
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:hystrix/group-key :default
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:hystrix/threads 10
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:hystrix/queue-size 5
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:hystrix/timeout-ms 1000
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:hystrix/breaker-request-volume 20
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:hystrix/breaker-error-percent 50
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:hystrix/breaker-sleep-window-ms 5000
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:hystrix/bad-request-pred client-error?})
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(def ^:private hystrix-keys
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(keys hystrix-base-configuration))
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(defn ^:private hystrix-defaults [defaults]
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(merge hystrix-base-configuration (select-keys defaults hystrix-keys)))
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4355
(defn ^:private group-key [s]
4456
(HystrixCommandGroupKey$Factory/asKey (name s)))
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@@ -49,13 +61,15 @@
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(defn ^:private configurator
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"Create a configurator that can configure the hystrix according to the
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declarative config (or some sensible defaults)"
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[config]
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(let [timeout (:hystrix/timeout-ms config 1000)
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group (:hystrix/group-key config :default)
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threads (:hystrix/threads config 10)
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request-volume (:hystrix/breaker-request-volume config 20)
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error-percent (:hystrix/breaker-error-percent config 50)
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sleep-window (:hystrix/breaker-sleep-window-ms config 5000)
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^HystrixCommand$Setter [config]
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(let [{group :hystrix/group-key
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command :hystrix/command-key
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timeout :hystrix/timeout-ms
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threads :hystrix/threads
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queue-size :hystrix/queue-size
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sleep-window :hystrix/breaker-sleep-window-ms
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error-percent :hystrix/breaker-error-percent
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request-volume :hystrix/breaker-request-volume} config
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command-configurator (doto (HystrixCommandProperties/Setter)
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(.withExecutionIsolationThreadTimeoutInMilliseconds timeout)
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(.withCircuitBreakerRequestVolumeThreshold request-volume)
@@ -64,10 +78,10 @@
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(.withMetricsRollingPercentileEnabled false))
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thread-pool-configurator (doto (HystrixThreadPoolProperties/Setter)
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(.withCoreSize threads)
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(.withMaxQueueSize (:hystrix/queue-size config 5))
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(.withQueueSizeRejectionThreshold (:hystrix/queue-size config 5)))]
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(.withMaxQueueSize queue-size)
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(.withQueueSizeRejectionThreshold queue-size))]
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(doto (HystrixCommand$Setter/withGroupKey (group-key group))
70-
(.andCommandKey (command-key (:hystrix/command-key config :default)))
84+
(.andCommandKey (command-key command))
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(.andCommandPropertiesDefaults command-configurator)
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(.andThreadPoolPropertiesDefaults thread-pool-configurator))))
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@@ -85,48 +99,65 @@
8599
(fn [req resp]
86100
(contains? status-codes (:status resp)))))
87101

88-
(defn client-error?
89-
"Returns true when the response has one of the 4xx family of status
90-
codes"
91-
[req resp]
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(http/client-error? resp))
93-
94-
(defn wrap-hystrix
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"Wrap a clj-http client request with hystrix features (but only if a
96-
command-key is present in the options map)."
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[f req]
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(if (not-empty (select-keys req hystrix-keys))
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(let [bad-request-pred (:hystrix/bad-request-pred req client-error?)
100-
fallback (:hystrix/fallback-fn req default-fallback)
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wrap-bad-request (fn [resp] (if (bad-request-pred req resp)
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(throw (HystrixBadRequestException. "Ignored bad request"
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(wrap {:object resp
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:message "Bad request pred"
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:stack-trace (stack-trace)})))
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resp))
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wrap-exception-response (fn [resp] ((http/wrap-exceptions (constantly resp)) (assoc req :throw-exceptions true)))
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^HystrixCommand$Setter configurator (configurator req)
109-
logging-context (or (MDC/getCopyOfContextMap) {})
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command (proxy [HystrixCommand] [configurator]
111-
(getFallback []
112-
(MDC/setContextMap logging-context)
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(log-error (:hystrix/command-key req) this)
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(let [exception (.getFailedExecutionException ^HystrixCommand this)
115-
response (when exception (get-thrown-object exception))]
116-
(fallback req response)))
117-
(run []
118-
(MDC/setContextMap logging-context)
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(-> req
120-
(assoc :throw-exceptions false)
121-
f
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wrap-bad-request
123-
wrap-exception-response)))]
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(handle-exception #(.execute command) req))
125-
(f req)))
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(defn hystrix-wrapper
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"Create a function that wraps clj-http client requests with hystrix features
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(but only if a hystrix key is present in the options map).
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Accepts a possibly empty map of default hystrix values that will be used as
106+
fallback configuration for each hystrix request."
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[custom-defaults]
108+
(let [defaults (hystrix-defaults custom-defaults)]
109+
(fn [f req]
110+
(if (not-empty (select-keys req hystrix-keys))
111+
(let [req (merge defaults req)
112+
bad-request-pred (:hystrix/bad-request-pred req)
113+
fallback (:hystrix/fallback-fn req)
114+
wrap-bad-request (fn [resp]
115+
(if (bad-request-pred req resp)
116+
(throw
117+
(HystrixBadRequestException.
118+
"Ignored bad request"
119+
(wrap {:object resp
120+
:message "Bad request pred"
121+
:stack-trace (stack-trace)})))
122+
resp))
123+
wrap-exception-response (fn [resp]
124+
((http/wrap-exceptions (constantly resp))
125+
(assoc req :throw-exceptions true)))
126+
configurator (configurator req)
127+
logging-context (or (MDC/getCopyOfContextMap) {})
128+
command (proxy [HystrixCommand] [configurator]
129+
(getFallback []
130+
(MDC/setContextMap logging-context)
131+
(log-error (:hystrix/command-key req) this)
132+
(let [exception (.getFailedExecutionException ^HystrixCommand this)
133+
response (when exception (get-thrown-object exception))]
134+
(fallback req response)))
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(run []
136+
(MDC/setContextMap logging-context)
137+
(-> req
138+
(assoc :throw-exceptions false)
139+
f
140+
wrap-bad-request
141+
wrap-exception-response)))]
142+
(handle-exception #(.execute command) req))
143+
(f req)))))
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127145
(defn add-hook
128146
"Activate clj-http-hystrix to wrap all clj-http client requests as
129-
hystrix commands."
147+
hystrix commands.
148+
Provide custom hystrix defaults by providing an optional defaults map:
149+
150+
;; use clj-http-hystrix.core default configuration
151+
(add-hook)
152+
153+
;; 6 second timeout fallback, if not specified in request
154+
(add-hook {:hystrix/timeout-ms 6000})
155+
"
156+
([] (add-hook {}))
157+
([defaults]
158+
(hooke/add-hook #'http/request ::wrap-hystrix (hystrix-wrapper defaults))))
159+
160+
(defn remove-hook
161+
"Deactivate clj-http-hystrix."
130162
[]
131-
(when-not (some-> (meta http/request) :robert.hooke/hooks deref (contains? #'wrap-hystrix))
132-
(hooke/add-hook #'http/request #'wrap-hystrix)))
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(hooke/remove-hook #'http/request ::wrap-hystrix))

‎test/clj_http_hystrix/core_test.clj‎

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Original file line numberDiff line numberDiff line change
@@ -4,6 +4,7 @@
44
[clj-http.client :as http]
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[clojure.java.io :refer [resource]]
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[clojure.tools.logging :refer [warn error]]
7+
[robert.hooke :as hooke]
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[rest-cljer.core :refer [rest-driven]]
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[midje.sweet :refer :all])
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(:import [java.net SocketTimeoutException]
@@ -171,3 +172,41 @@
171172
(predicate {} {:status 101}) => false
172173
(predicate {} {:status 202}) => false
173174
(predicate {} {:status 299}) => false))
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176+
(defn get-hooks []
177+
(some-> http/request meta :robert.hooke/hooks deref))
178+
179+
(fact "add-hook can be safely called more than once"
180+
(count (get-hooks)) => 1
181+
(contains? (get-hooks) :clj-http-hystrix.core/wrap-hystrix) => true
182+
;call add-hook a few more times and ensure only one hook is present
183+
(add-hook), (add-hook)
184+
(count (get-hooks)) => 1
185+
(contains? (get-hooks) :clj-http-hystrix.core/wrap-hystrix) => true)
186+
187+
(fact "remove-hook removes clj-http-hystrix hook"
188+
(count (get-hooks)) => 1
189+
(contains? (get-hooks) :clj-http-hystrix.core/wrap-hystrix) => true
190+
(remove-hook)
191+
(get-hooks) => nil
192+
;can be called more than once
193+
(remove-hook), (remove-hook)
194+
(get-hooks) => nil
195+
;restore hook for additional testing
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(add-hook))
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198+
(fact "add-hook with user-defaults will override base configuration, but not call configuration"
199+
(rest-driven
200+
[{:method :GET
201+
:url "/"}
202+
{:status 500
203+
:times 3}]
204+
(make-hystrix-call {})
205+
=> (throws clojure.lang.ExceptionInfo "clj-http: status 500")
206+
;set custom default for fallback-fn
207+
(remove-hook)
208+
(add-hook {:hystrix/fallback-fn (constantly "bar")})
209+
(make-hystrix-call {}) => "bar"
210+
(make-hystrix-call {:hystrix/fallback-fn (constantly "baz")}) => "baz")
211+
(remove-hook)
212+
(add-hook))

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