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tweaks to hopefully remove any potential concurrency issues

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trying to reduce the number of times i de-reference session-atom, as
well as reduce the number of bits of data i obtain from it before/after
a call to swap! within the same function. was able to cut out a few
here which i think should be pretty good. :-)
This commit is contained in:
Gered 2022-01-04 19:51:30 -05:00
parent 52dd71f26b
commit 6550dc4450
1 changed files with 12 additions and 10 deletions
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22
src/aging_session/core.clj
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@ -83,15 +83,17 @@
SessionStore SessionStore
(read-session [_ key] (read-session [_ key]
(when-let [existing-entry (get @session-atom key)] (when (contains? @session-atom key)
(let [session-map (swap! session-atom process-read-entry ttl key refresh-on-read)] (let [[previous current] (swap-vals! session-atom process-read-entry ttl key refresh-on-read)]
; if the entry we were about to read had expired, session-map will not have it anymore at this point ; if the entry we were about to read had expired, session-map will not have it anymore at this point
(if (contains? session-map key) (if (contains? current key)
(-> session-map ; note: performs faster than get-in (-> current ; note: performs faster than get-in
(get key) (get key)
(get :value)) (get :value))
(when on-removal (when (and on-removal
(on-removal key (:value existing-entry) :expired) ; just in case there was a last second change by other concurrently running actions ...
(contains? previous key))
(on-removal key (-> previous (get key) :value) :expired)
nil))))) nil)))))
(write-session [_ key data] (write-session [_ key data]
@ -99,13 +101,13 @@
(swap! op-counter inc)) (swap! op-counter inc))
(let [key (or key (unique-id))] (let [key (or key (unique-id))]
(if on-removal (if on-removal
; when we have an on-removal listener, we need to check if we are about to overwrite an entry ; when we have an on-removal listener, we need to check if we are overwriting an entry
; that has already expired, and if so, call on-removal for it ; that has already expired, and if so, call on-removal for it
; (note that if it has ALREADY expired, yes, we're about to overwrite this entry anyway, but ; (note that if it has ALREADY expired, yes, we're about to overwrite this entry anyway, but
; we DO need to treat it as an expiry, because the old value expired ...) ; we DO need to treat it as an expiry, because the old value expired ...)
(let [existing-entry (get @session-atom key) (let [[previous current] (swap-vals! session-atom process-write-entry key data refresh-on-write)
expired? (entry-expired? ttl existing-entry)] existing-entry (get previous key)
(swap! session-atom process-write-entry key data refresh-on-write) expired? (entry-expired? ttl existing-entry)]
(if expired? (if expired?
(on-removal key (:value existing-entry) :expired))) (on-removal key (:value existing-entry) :expired)))
; if there's no on-removal listener, we can simply process the write ; if there's no on-removal listener, we can simply process the write