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janosmeszarosJanos MeszarosJanos Meszaros
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Add ability to handle async Ring requests (#19)
* Making instrumentation async ready * Handling async requests on exposing metrics * Simplifying handler invocation * Handling sync exceptions for async handler * Adding note about async ring support. --------- Co-authored-by: Janos Meszaros <jmeszaros@whitepages.com> Co-authored-by: Janos Meszaros <jmeszaros@ekata.com>
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‎README.md‎

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@@ -30,7 +30,7 @@ tasks.
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- [Standalone HTTP Server](#standalone-http-server)
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- [History](#history)
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- [License](#license)
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## Basic Usage <a name="basic-usage"></a>
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@@ -324,6 +324,8 @@ These are, purposefully, compatible with the metrics produced by
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[prometheus-clj](https://github.com/soundcloud/prometheus-clj), as to allow a
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smooth migration.
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Ring supports sync and async [handlers](https://github.com/ring-clojure/ring/wiki/Concepts#handlers), metrics are collected for both by `iapetos.collector.ring` ns.
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#### Exception Handling <a name="exception-handling"></a>
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By default, if your ring handler throws an exception, only the `http_exceptions_total` counter would be incremented.
@@ -332,12 +334,12 @@ This means that if you respond with a 500 error code on exceptions:
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1. These responses won't be counted on `http_requests_total`
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2. Their latencies won't be observed on `http_request_latency_seconds`
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To overcome this, you can use the optional `:exception-status` to define a status code to be reported
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To overcome this, you can use the optional `:exception-status` to define a status code to be reported
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on both metrics, for example:
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```clojure
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(def app
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(-> (fn [_] (throw (Exception.)))
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(-> (fn [_] (throw (Exception.)))
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(ring/wrap-metrics registry {:path "/metrics" :exception-status 500})))
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```
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‎src/iapetos/collector/ring.clj‎

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@@ -30,24 +30,24 @@
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(defn- make-latency-collector
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[labels buckets]
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(prometheus/histogram
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:http/request-latency-seconds
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{:description "the response latency for HTTP requests."
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:labels (concat [:method :status :statusClass :path] labels)
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:buckets buckets}))
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:http/request-latency-seconds
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{:description "the response latency for HTTP requests."
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:labels (concat [:method :status :statusClass :path] labels)
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:buckets buckets}))
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(defn- make-count-collector
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[labels]
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(prometheus/counter
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:http/requests-total
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{:description "the total number of HTTP requests processed."
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:labels (concat [:method :status :statusClass :path] labels)}))
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:http/requests-total
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{:description "the total number of HTTP requests processed."
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:labels (concat [:method :status :statusClass :path] labels)}))
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(defn- make-exception-collector
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[labels]
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(ex/exception-counter
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:http/exceptions-total
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{:description "the total number of exceptions encountered during HTTP processing."
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:labels (concat [:method :path] labels)}))
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:http/exceptions-total
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{:description "the total number of exceptions encountered during HTTP processing."
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:labels (concat [:method :path] labels)}))
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(defn initialize
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"Initialize all collectors for Ring handler instrumentation. This includes:
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& [{:keys [latency-histogram-buckets labels]
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:or {latency-histogram-buckets [0.001 0.005 0.01 0.02 0.05 0.1 0.2 0.3 0.5 0.75 1 5]}}]]
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(prometheus/register
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registry
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(make-latency-collector labels latency-histogram-buckets)
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(make-count-collector labels)
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(make-exception-collector labels)))
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registry
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(make-latency-collector labels latency-histogram-buckets)
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(make-count-collector labels)
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(make-exception-collector labels)))
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;; ## Response
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(defn- record-metrics!
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[{:keys [registry] :as options} delta request response]
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(let [labels (merge
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{:status (status response)
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:statusClass (status-class response)}
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(labels-for options request response))
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{:status (status response)
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:statusClass (status-class response)}
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(labels-for options request response))
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delta-in-seconds (/ delta 1e9)]
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(-> registry
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(prometheus/inc :http/requests-total labels)
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(f)))
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(defn- run-instrumented
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[{:keys [handler exception-status] :as options} request]
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(ex/with-exceptions (exception-counter-for options request)
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(let [start-time (System/nanoTime)
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response (safe exception-status #(handler request))
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delta (- (System/nanoTime) start-time)]
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(->> (ensure-response-map response exception-status)
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(record-metrics! options delta request))
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(if-not (exception? response)
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response
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(throw response)))))
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([{:keys [handler exception-status] :as options} request]
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(ex/with-exceptions (exception-counter-for options request)
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(let [start-time (System/nanoTime)
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response (safe exception-status #(handler request))
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delta (- (System/nanoTime) start-time)]
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(->> exception-status
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(ensure-response-map response)
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(record-metrics! options delta request))
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(if-not (exception? response)
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response
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(throw response)))))
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([{:keys [handler exception-status] :as options} request respond raise]
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(let [start-time (System/nanoTime)
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ex-counter (exception-counter-for options request)
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respond-fn #(let [delta (- (System/nanoTime) start-time)
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_ (->> exception-status
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(ensure-response-map %)
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(record-metrics! options delta request))]
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(respond %))
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raise-fn #(let [delta (- (System/nanoTime) start-time)]
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(when exception-status
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(->> exception-status
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(ensure-response-map %)
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(record-metrics! options delta request)))
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(ex/record-exception! ex-counter %)
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(raise %))]
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(try
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(handler request respond-fn raise-fn)
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(catch Throwable t
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(ex/record-exception! ex-counter t)
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(raise t))))))
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(defn- run-expose
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([{:keys [path on-request registry handler] :as options}
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{:keys [request-method uri] :as request}]
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(if (= uri path)
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(if (= request-method :get)
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(do
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(on-request registry)
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(metrics-response registry))
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{:status 405})
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(handler request)))
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([{:keys [path on-request registry handler] :as options}
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{:keys [request-method uri] :as request}
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respond
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raise]
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(if (= uri path)
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(if (= request-method :get)
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(do
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(on-request registry)
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(respond (metrics-response registry)))
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(respond {:status 405}))
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(handler request respond raise))))
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(defn ring-fn [f options]
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(fn
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([request] (f options request))
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([request respond raise] (f options request respond raise))))
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(defn wrap-instrumentation
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"Wrap the given Ring handler to write metrics to the given registry:
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[[initialize]]."
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[handler registry
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& [{:keys [path-fn label-fn]
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:or {path-fn :uri
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label-fn (constantly {})}
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:as options}]]
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:or {path-fn :uri
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label-fn (constantly {})}
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:as options}]]
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(let [options (assoc options
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:path-fn path-fn
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:label-fn label-fn
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:registry registry
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:handler handler)]
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#(run-instrumented options %)))
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(ring-fn run-instrumented options)))
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;; ### Metrics Endpoint
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the Prometheus scraper as a trigger for metrics collection."
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[handler registry
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& [{:keys [path on-request]
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:or {path "/metrics"
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on-request identity}}]]
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(fn [{:keys [request-method uri] :as request}]
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(if (= uri path)
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(if (= request-method :get)
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(do
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(on-request registry)
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(metrics-response registry))
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{:status 405})
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(handler request))))
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:or {path "/metrics"
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on-request identity}
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:as options}]]
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(let [options (assoc options
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:path path
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:on-request on-request
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:registry registry
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:handler handler)]
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(ring-fn run-expose options)))
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;; ### Compound Middleware
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