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(PE-37592) Compress events for the same changed-path #32

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Oct 29, 2024
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(PE-37592) Compress events for the same changed-path #32

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57 changes: 52 additions & 5 deletions src/clj/puppetlabs/trapperkeeper/services/watcher/filesystem_watch_core.clj
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
(ns puppetlabs.trapperkeeper.services.watcher.filesystem-watch-core
(:require [clojure.tools.logging :as log]
(:require [clojure.set :as set]
[clojure.tools.logging :as log]
[me.raynes.fs :as fs]
[schema.core :as schema]
[puppetlabs.i18n.core :refer [trs]]
Expand Down Expand Up @@ -175,14 +176,60 @@
(= (.toPath ^File (:changed-path event)) (:file callback-entry)))))]
(filter filter-fn events)))

(defn ->tuple
"Create a tuple of the two fields we care about in an Event.
This simple element querying our sets simple."
[event]
[(:changed-path event) (:type event)])

(defn already-seen?
"Expects a set of event tuples (see ->tuple) and a full Event.
Is this a modify event for a changed-path where we've already seen a create or modify event?"
[events {:keys [changed-path type] :as _event}]
(when (= :modify type)
(or (set/subset? #{[changed-path :create]} events)
(set/subset? #{[changed-path :modify]} events))))

(defn should-overwrite?
"Expects a set of event tuples (see ->tuple) and a full Event.
Is this a create event that should supersede a previously found modify or create event?"
[events {:keys [changed-path type] :as _event}]
(when (= :create type)
(or (set/subset? #{[changed-path :modify]} events)
(set/subset? #{[changed-path :create]} events))))

(defn reducible-remove
[{:keys [tuples] :as memo} item]
(cond
;; Ignore the new item if we've already seen a value representing it
(already-seen? tuples item)
memo
;; Remove old value and replace it with the new value
(should-overwrite? tuples item)
(-> memo
(update :tuples set/difference #{[(:changed-path item) :modify]})
(update :tuples set/union #{(->tuple item)})
(update :events (fn [es] (filter #(and (= (:changed-path item) (:changed-path %))
(or
(= :modify (:type %))
(= :create (:type %))))
es)))
(update :events conj item))
;; default add the event to our tracker
:else
(-> memo
(update :tuples set/union #{(->tuple item)})
(update :events conj item))))

(schema/defn process-events!
"Process for side effects any events that occurred for watcher's watch-key"
[watcher :- (schema/protocol Watcher)
events :- [Event]]
(let [callbacks @(:callbacks watcher)]
(let [callbacks @(:callbacks watcher)
compressed-events (->> events (reduce reducible-remove {:tuples #{} :events []}) :events)]
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Would all events have the same changed-path? In other words, is a collection of events here for a single file?

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Answer is yes! We need to manage the compression per changed path.

;; avoid doing a potentially expensive walk when we aren't logging at :debug
(when (log/enabled? :debug)
(let [events-by-dir (group-by :watched-path events)]
(let [events-by-dir (group-by :watched-path compressed-events)]
(doseq [[dir events'] events-by-dir]
(log/debug (trs "Got {0} event(s) in directory {1}"
(count events') dir)))))
Expand All @@ -191,10 +238,10 @@
(when (log/enabled? :trace)
(log/tracef "%s\n%s"
(trs "Events:")
(ks/pprint-to-string events)))
(ks/pprint-to-string compressed-events)))

(doseq [callback-entry callbacks]
((:callback callback-entry) (filter-events callback-entry events)))))
((:callback callback-entry) (filter-events callback-entry compressed-events)))))

(schema/defn watch! :- Future
"Creates and returns a future. Processes events for the passed in watcher within the context of that future.
Expand Down
22 changes: 14 additions & 8 deletions test/puppetlabs/trapperkeeper/services/watcher/filesystem_watch_service_test.clj
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Original file line number Diff line number Diff line change
Expand Up @@ -23,9 +23,13 @@
(fn [events]
(swap! dest concat events)))

(defn format-events
[dest]
(set (map #(select-keys % [:changed-path :type]) @dest)))

(defn contains-events?
[dest events]
(let [select-keys-set (set (map #(select-keys % [:changed-path :type]) @dest))]
(let [select-keys-set (format-events dest)]
(set/subset? events select-keys-set)))

(defn exactly-matches-event?
Expand All @@ -47,7 +51,7 @@
(loop []
(let [elapsed-time (- (System/currentTimeMillis) start-time)]
(if (contains-events? dest events)
events
(format-events dest)
(if (< elapsed-time timeout-ms)
(do (Thread/sleep 100)
(recur))
Expand Down Expand Up @@ -100,9 +104,6 @@
(spit first-file "foo")
(let [events #{{:changed-path first-file
:type :create}}]
;; This is the first of many weird assertions like this, but it's done
;; this way on purpose to get decent reporting from failed assertions.
;; See above the docstring on wait-for-events.
(is (= events (wait-for-events results events)))))
(testing "callback invoked again when another new file is created"
(reset! results [])
Expand Down Expand Up @@ -144,6 +145,7 @@
(let [events #{{:changed-path sub-dir
:type :create}}]
(is (= events (wait-for-events results events))))
(reset! results [])
(is (fs/delete sub-dir))
(let [events #{{:changed-path sub-dir
:type :delete}}]
Expand Down Expand Up @@ -260,8 +262,8 @@
(reset! results [])
(is (fs/delete first-file))
(is (fs/delete second-file))
(let [events [{:changed-path first-file
:type :delete}]]
(let [events #{{:changed-path first-file
:type :delete}}]
(is (= events (wait-for-events results events))))))
(testing "re-creation of a deleted directory"
(reset! results [])
Expand Down Expand Up @@ -444,7 +446,7 @@
(is (fs/delete-dir intermediate-dir))
(let [events #{{:changed-path intermediate-dir
:type :delete}}]
(is (= events (wait-for-events results events)))))
(is (every? #(= :delete (:type %)) (wait-for-events results events)))))
(let [another-nested-dir (fs/file root-dir "another-nested-dir")
new-nested-file (fs/file another-nested-dir "new-nested-file")]
(testing "new nested directory"
Expand All @@ -464,6 +466,8 @@
(reset! results [])
(is (fs/delete-dir another-nested-dir))
(let [events #{{:changed-path another-nested-dir
:type :delete}
{:changed-path new-nested-file
:type :delete}}]
(is (= events (wait-for-events results events)))))))))))

Expand Down Expand Up @@ -628,6 +632,8 @@
(testing "Deletion thereof"
(is (fs/delete-dir nested-dir))
(let [events #{{:changed-path nested-dir
:type :delete}
{:changed-path test-file-nested
:type :delete}}]
(is (= events (wait-for-events results events))))
(reset! results [])
Expand Down
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