Merge pull request #1078 from metabase/task_reloading_fix

Task/Events reloading fix

src/metabase/events.clj

 (ns metabase.events
   "Provides a very simply event bus using `core.async` to allow publishing and subscribing to intersting
-   topics happening throughout the Metabase system in a decoupled way."
+   topics happening throughout the Metabase system in a decoupled way.
+
+   ## Regarding Events Initialization:
+
+   The most appropriate way to initialize event listeners in any `metabase.events.*` namespace is to implement the
+   `events-init` function which accepts zero arguments.  This function is dynamically resolved and called exactly
+   once when the application goes through normal startup procedures.  Inside this function you can do any work
+   needed and add your events subscribers to the bus as usual via `start-event-listener`."
   (:require clojure.java.classpath
             [clojure.core.async :as async]
             [clojure.tools.logging :as log]
@@ -22,7 +29,9 @@
        set
        (map (fn [events-ns]
               (log/info "\tloading events namespace: " events-ns)
-              (require events-ns)))
+              (require events-ns)
+              ;; look for `events-init` function in the namespace and call it if it exists
+              ((ns-resolve events-ns 'events-init))))
        dorun))
 
 (defn initialize-events!

src/metabase/events/activity_feed.clj

@@ -122,7 +122,7 @@
 ;;; ## ---------------------------------------- LIFECYLE ----------------------------------------
 
 
-;; this is what actually kicks off our listener for events
-(when (config/is-prod?)
-  (log/info "Starting activity-feed events listener")
-  (events/start-event-listener activity-feed-topics activity-feed-channel process-activity-event))
+(defn events-init []
+  (when-not (config/is-test?)
+    (log/info "Starting activity-feed events listener")
+    (events/start-event-listener activity-feed-topics activity-feed-channel process-activity-event)))

src/metabase/events/revision.clj

@@ -54,7 +54,7 @@
 ;;; ## ---------------------------------------- LIFECYLE ----------------------------------------
 
 
-;; this is what actually kicks off our listener for events
-(when (config/is-prod?)
-  (log/info "Starting revision events listener")
-  (events/start-event-listener revisions-topics revisions-channel process-revision-event))
+(defn events-init []
+  (when-not (config/is-test?)
+    (log/info "Starting revision events listener")
+    (events/start-event-listener revisions-topics revisions-channel process-revision-event)))

src/metabase/events/sync_database.clj

@@ -39,7 +39,7 @@
 ;;; ## ---------------------------------------- LIFECYLE ----------------------------------------
 
 
-;; this is what actually kicks off our listener for events
-(when (config/is-prod?)
-  (log/info "Starting database sync events listener")
-  (events/start-event-listener sync-database-topics sync-database-channel process-sync-database-event))
+(defn events-init []
+  (when-not (config/is-test?)
+    (log/info "Starting database sync events listener")
+    (events/start-event-listener sync-database-topics sync-database-channel process-sync-database-event)))

src/metabase/events/view_log.clj

@@ -47,7 +47,7 @@
 ;;; ## ---------------------------------------- LIFECYLE ----------------------------------------
 
 
-;; this is what actually kicks off our listener for events
-(when (config/is-prod?)
-  (log/info "Starting view-log events listener")
-  (events/start-event-listener view-counts-topics view-counts-channel process-view-count-event))
+(defn events-init []
+  (when-not (config/is-test?)
+    (log/info "Starting view-log events listener")
+    (events/start-event-listener view-counts-topics view-counts-channel process-view-count-event)))

src/metabase/task.clj

 (ns metabase.task
-  "Background task scheduling via Quartzite.  Individual tasks are defined in `metabase.task.*`"
+  "Background task scheduling via Quartzite.  Individual tasks are defined in `metabase.task.*`.
+
+   ## Regarding Task Initialization:
+
+   The most appropriate way to initialize tasks in any `metabase.task.*` namespace is to implement the
+   `task-init` function which accepts zero arguments.  This function is dynamically resolved and called
+   exactly once when the application goes through normal startup procedures.  Inside this function you
+   can do any work needed and add your task to the scheduler as usual via `schedule-task!`."
   (:require clojure.java.classpath
             [clojure.tools.logging :as log]
             [clojure.tools.namespace.find :as ns-find]
@@ -18,7 +25,9 @@
        set
        (map (fn [events-ns]
               (log/info "\tloading tasks namespace: " events-ns)
-              (require events-ns)))
+              (require events-ns)
+              ;; look for `task-init` function in the namespace and call it if it exists
+              ((ns-resolve events-ns 'task-init))))
        dorun))
 
 (defn start-scheduler!

src/metabase/task/sync_databases.clj

@@ -27,8 +27,7 @@
         (catch Exception e
           (log/error "Error syncing database: " (:id database) e))))))
 
-;; this is what actually adds our task to the scheduler
-(when (config/is-prod?)
+(defn task-init []
   (log/info "Submitting sync-database task to scheduler")
   ;; build our job
   (reset! sync-databases-job (jobs/build