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fix: prevent event-listener leaks

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rcmerci
2025-04-18 12:09:08 +08:00
parent 7365058717
commit 2a978065f0
1 changed files with 66 additions and 48 deletions
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114
src/main/frontend/worker/shared_service.cljs
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@@ -2,20 +2,27 @@
"This allows multiple workers to share some resources (e.g. db access)"
(:require [cljs-bean.core :as bean]
[goog.object :as gobj]
[lambdaisland.glogi :as log]
[promesa.core :as p]))
;; TODO:
;; - client-channel close before re-creating new one
;; - There is a problem of duplicate event listener registrations.
;; Idea and code copied from https://github.com/Matt-TOTW/shared-service/blob/master/src/sharedService.ts
;; Related thread: https://github.com/rhashimoto/wa-sqlite/discussions/81
(defonce *master-client? (atom false))
;;; common-channel - Communication related to master-client election.
;; FIXME: but 'sync-db-changes' events are tranferred on this channel
;;; client-channel - For API request-response data communication.
(defonce *common-channel (atom nil))
(defonce *client-channel (atom nil))
;;; record channel-listener here, to able to remove old listener before we addEventListener new one
(defonce *common-channel-listener (atom nil))
;;(defonce *client-channel-listener (atom nil))
(defonce *requests-in-flight (atom {}))
;;; The unique identity of the context where `js/navigator.locks.request` is called
(defonce *client-id (atom nil))
@@ -110,70 +117,81 @@
(reset! *common-channel channel)
channel)))
(defn- listen-common-channel
[common-channel listener-fn]
(when-let [old-listener @*common-channel-listener]
(.removeEventListener common-channel "message" old-listener))
(reset! *common-channel-listener listener-fn)
(.addEventListener common-channel "message" listener-fn))
(defn- slave-registered-handler
[service-name slave-client-id event *register-finish-promise?]
(let [slave-client-id* (:slave-client-id event)]
(when (= slave-client-id slave-client-id*)
(js/navigator.locks.request service-name #js {:mode "exclusive"}
(fn [_lock]
;; The master has gone, elect the new master
(prn :debug "master has gone")
(reset! *master-client? :re-check)))
(p/resolve! @*register-finish-promise?))))
(defn- on-become-slave
[slave-client-id service-name common-channel status-ready-deferred-p]
[slave-client-id service-name common-channel status-ready-promise]
(reset! *client-channel (js/BroadcastChannel. (get-broadcast-channel-name slave-client-id service-name)))
(let [register
(fn register []
(p/create
(fn [resolve-fn _]
(letfn [(listener [event]
(let [{:keys [_master-client-id type]
slave-client-id* :slave-client-id} (bean/->clj (.-data event))]
(when (and (= slave-client-id* slave-client-id) (= type "slave-registered"))
(js/navigator.locks.request service-name #js {:mode "exclusive"}
(fn [_lock]
;; The master has gone, elect the new master
(prn :debug "master has gone")
(reset! *master-client? :re-check)))
(.removeEventListener common-channel "message" listener)
(resolve-fn nil))))]
(.addEventListener common-channel "message" listener)
(.postMessage common-channel #js {:type "slave-register" :slave-client-id slave-client-id})))))]
(.addEventListener common-channel "message"
(fn [event]
(let [{:keys [type data]} (bean/->clj (.-data event))]
(case type
"master-changed"
(p/do!
(js/console.log "master-client change detected. Re-registering...")
(register)
(when (seq @*requests-in-flight)
(js/console.log "Requests were in flight when master changed. Requeuing...")
(p/all (map
(fn [[id {:keys [method args resolve-fn reject-fn]}]]
(let [listener (get-on-request-listener id resolve-fn reject-fn)]
(when-let [channel @*client-channel]
(.addEventListener channel "message" listener)
(.postMessage channel (bean/->js {:id id
:type "request"
:method method
:args args})))))
@*requests-in-flight))))
(let [*register-finish-promise? (atom nil)
<register #(do (.postMessage common-channel #js {:type "slave-register"
:slave-client-id slave-client-id})
(reset! *register-finish-promise? (p/deferred))
@*register-finish-promise?)]
(listen-common-channel
common-channel
(fn [event]
(let [{:keys [type data] :as event*} (bean/->clj (.-data event))]
(case type
"master-changed"
(p/do!
(js/console.log "master-client change detected. Re-registering...")
(<register)
(when (seq @*requests-in-flight)
(js/console.log "Requests were in flight when master changed. Requeuing...")
(p/all (map
(fn [[id {:keys [method args resolve-fn reject-fn]}]]
(let [listener (get-on-request-listener id resolve-fn reject-fn)]
(when-let [channel @*client-channel]
(.addEventListener channel "message" listener)
(.postMessage channel (bean/->js {:id id
:type "request"
:method method
:args args})))))
@*requests-in-flight))))
"slave-registered"
(slave-registered-handler service-name slave-client-id event* *register-finish-promise?)
"sync-db-changes"
(.postMessage js/self data)
"sync-db-changes"
(.postMessage js/self data)
nil))))
"slave-register"
(log/info :ignored-event event*)))))
(->
(p/do!
(register)
(p/resolve! status-ready-deferred-p))
(p/catch (fn [error]
(js/console.error error))))))
(<register)
(p/resolve! status-ready-promise))
(p/catch (fn [e]
(js/console.error e)
(p/rejected e))))))
(defn- on-become-master
[master-client-id service-name common-channel target on-become-master-handler status-ready-deferred-p]
(prn :debug :become-master master-client-id :service service-name)
(.addEventListener
common-channel "message"
(listen-common-channel
common-channel
(fn [event]
(let [{:keys [slave-client-id type]} (bean/->clj (.-data event))]
(when (= type "slave-register")
(let [client-channel (js/BroadcastChannel. (get-broadcast-channel-name slave-client-id service-name))]
(js/navigator.locks.request slave-client-id #js {:mode "exclusive"}
(fn [_]
;; The client has gone. Clean up
;; The client has gone. Clean up
(.close client-channel)))
(.addEventListener client-channel "message"