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✨ Improve msgbus subscription handling.
This commit is contained in:
Andrey Antukh
parent
8fd37dbad5
commit
7e1ee087d3
4 changed files with 194 additions and 124 deletions
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@ -62,9 +62,14 @@
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snd-conn (.connect ^RedisClient rclient ^RedisCodec codec)
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rcv-conn (.connectPubSub ^RedisClient rclient ^RedisCodec codec)
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pub-buff (a/chan (a/dropping-buffer buffer-size))
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rcv-buff (a/chan (a/dropping-buffer buffer-size))
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sub-buff (a/chan 1)
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;; Channel used for receive publications from the application.
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pub-chan (a/chan (a/dropping-buffer buffer-size))
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;; Channel used for receive data from redis
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rcv-chan (a/chan (a/dropping-buffer buffer-size))
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;; Channel used for receive subscription requests.
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sub-chan (a/chan)
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cch (a/chan 1)]
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(.setTimeout ^StatefulRedisConnection snd-conn ^Duration (dt/duration {:seconds 10}))
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@ -73,10 +78,10 @@
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(log/debugf "initializing msgbus (uri: '%s')" (str uri))
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;; Start the sending (publishing) loop
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(impl-publish-loop snd-conn pub-buff cch)
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(impl-publish-loop snd-conn pub-chan cch)
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;; Start the receiving (subscribing) loop
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(impl-subscribe-loop rcv-conn rcv-buff sub-buff cch)
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(impl-subscribe-loop rcv-conn rcv-chan sub-chan cch)
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(with-meta
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(fn run
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@ -84,14 +89,14 @@
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([command params]
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(a/go
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(case command
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:pub (a/>! pub-buff params)
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:sub (a/>! sub-buff params)))))
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:pub (a/>! pub-chan params)
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:sub (a/>! sub-chan params)))))
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{::snd-conn snd-conn
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::rcv-conn rcv-conn
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::cch cch
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::pub-buff pub-buff
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::rcv-buff rcv-buff})))
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::pub-chan pub-chan
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::rcv-chan rcv-chan})))
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(defmethod ig/halt-key! ::msgbus
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[_ f]
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@ -99,14 +104,14 @@
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(.close ^StatefulRedisConnection (::snd-conn mdata))
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(.close ^StatefulRedisPubSubConnection (::rcv-conn mdata))
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(a/close! (::cch mdata))
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(a/close! (::pub-buff mdata))
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(a/close! (::rcv-buff mdata))))
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(a/close! (::pub-chan mdata))
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(a/close! (::rcv-chan mdata))))
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(defn- impl-publish-loop
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[conn pub-buff cch]
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[conn pub-chan cch]
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(let [rac (.async ^StatefulRedisConnection conn)]
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(a/go-loop []
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(let [[val _] (a/alts! [cch pub-buff] :priority true)]
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(let [[val _] (a/alts! [cch pub-chan] :priority true)]
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(when (some? val)
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(let [result (a/<! (impl-redis-pub rac val))]
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(when (ex/exception? result)
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@ -114,7 +119,7 @@
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(recur))))))
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(defn- impl-subscribe-loop
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[conn rcv-buff sub-buff cch]
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[conn rcv-chan sub-chan cch]
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;; Add a unique listener to connection
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(.addListener conn (reify RedisPubSubListener
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(message [it pattern topic message])
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@ -122,48 +127,96 @@
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;; There are no back pressure, so we use a slidding
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;; buffer for cases when the pubsub broker sends
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;; more messages that we can process.
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(a/>!! rcv-buff {:topic topic :message (blob/decode message)}))
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(let [val {:topic topic :message (blob/decode message)}]
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(when-not (a/offer! rcv-chan val)
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(log/warn "dropping message on subscription loop"))))
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(psubscribed [it pattern count])
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(punsubscribed [it pattern count])
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(subscribed [it topic count])
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(unsubscribed [it topic count])))
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(a/go-loop [chans {}]
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(let [[val port] (a/alts! [sub-buff cch rcv-buff] :priority true)]
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(cond
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;; Stop condition; just do nothing
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(= port cch)
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nil
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(let [chans (agent {} :error-handler #(log/error % "unexpected error on agent"))
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;; If we receive a message on sub-buff this means that a new
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;; subscription is requested by the notifications module.
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(= port sub-buff)
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(let [topic (:topic val)
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output (:chan val)
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chans (update chans topic (fnil conj #{}) output)]
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(when (= 1 (count (get chans topic)))
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(let [result (a/<! (impl-redis-sub conn topic))]
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(when (ex/exception? result)
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(log/errorf result "unexpected exception on subscribing to '%s'" topic))))
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(recur chans))
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subscribe-to-single-topic
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(fn [nsubs topic chan]
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(let [nsubs (if (nil? nsubs) #{chan} (conj nsubs chan))]
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(when (= 1 (count nsubs))
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(let [result (a/<!! (impl-redis-sub conn topic))]
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(log/tracef "opening subscription to %s" topic)
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(when (ex/exception? result)
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(log/errorf result "unexpected exception on subscribing to '%s'" topic))))
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nsubs))
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;; This means we receive data from redis and we need to
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;; forward it to the underlying subscriptions.
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(= port rcv-buff)
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(let [topic (:topic val)
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pending (loop [chans (seq (get chans topic))
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pending #{}]
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(if-let [ch (first chans)]
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(if (a/>! ch (:message val))
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(recur (rest chans) pending)
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(recur (rest chans) (conj pending ch)))
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pending))
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chans (update chans topic #(reduce disj % pending))]
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(when (empty? (get chans topic))
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(let [result (a/<! (impl-redis-unsub conn topic))]
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(when (ex/exception? result)
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(log/errorf result "unexpected exception on unsubscribing from '%s'" topic))))
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(recur chans))))))
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subscribe-to-topics
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(fn [state topics chan]
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(let [topics (into #{} (map str) topics)
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state (update state :chans assoc chan topics)]
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(reduce (fn [state topic]
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(update-in state [:topics topic] subscribe-to-single-topic topic chan))
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state
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topics)))
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unsubscribe-from-single-topic
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(fn [nsubs topic chan]
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;; (log/tracef "unsubscribe-from-single-topic %s | %s | %s" nsubs topic chan)
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(let [nsubs (disj nsubs chan)]
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(when (empty? nsubs)
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(let [result (a/<!! (impl-redis-unsub conn topic))]
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(log/tracef "closing subscription to %s" topic)
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(when (ex/exception? result)
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(log/errorf result "unexpected exception on unsubscribing from '%s'" topic))))
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nsubs))
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unsubscribe-channels
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(fn [state pending]
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;; (log/tracef "unsubscribe-channels %s" (pr-str pending))
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(reduce (fn [state ch]
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(let [topics (get-in state [:chans ch])
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state (update state :chans dissoc ch)]
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;; (log/tracef "unsubscribe-channels topics=%s" topics)
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(reduce (fn [state topic]
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(update-in state [:topics topic] unsubscribe-from-single-topic topic ch))
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state
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topics)))
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state
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pending))]
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;; Asynchronous subscription loop; terminates when sub-chan is
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;; closed.
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(a/go-loop []
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(when-let [{:keys [topics chan]} (a/<! sub-chan)]
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(send-off chans subscribe-to-topics topics chan)
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(recur)))
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(a/go-loop []
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(let [[val port] (a/alts! [cch rcv-chan])]
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(cond
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;; Stop condition; close all underlying subscriptions and
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;; exit. The close operation is performed asynchronously.
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(= port cch)
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(send-off chans (fn [state]
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(log/tracef "close")
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(->> (vals state)
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(mapcat identity)
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(filter some?)
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(run! a/close!))))
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;; This means we receive data from redis and we need to
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;; forward it to the underlying subscriptions.
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(= port rcv-chan)
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(let [topic (:topic val) ; topic is already string
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pending (loop [chans (seq (get-in @chans [:topics topic]))
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pending #{}]
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(if-let [ch (first chans)]
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(if (a/>! ch (:message val))
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(recur (rest chans) pending)
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(recur (rest chans) (conj pending ch)))
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pending))]
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;; (log/tracef "received message => pending: %s" (pr-str pending))
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(some->> (seq pending)
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(send-off chans unsubscribe-channels))
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(recur)))))))
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(defn- impl-redis-pub
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[rac {:keys [topic message]}]
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