node-cache · doc-han · Jul 6, 2021 · Nov 11, 2021
diff --git a/_src/lib/node_cache.coffee b/_src/lib/node_cache.coffee
@@ -31,6 +31,8 @@ module.exports = class NodeCache extends EventEmitter
 			enableLegacyCallbacks: false
 			# max amount of keys that are being stored
 			maxKeys: -1
+			# auto replace oldest cache when maxKeys is reached
+			replaceOldestKey: false
 		, @options )
 
 		# generate functions with callbacks (legacy)
@@ -160,8 +162,18 @@ module.exports = class NodeCache extends EventEmitter
 	set: ( key, value, ttl )=>
 		# check if cache is overflowing
 		if (@options.maxKeys > -1 && @stats.keys >= @options.maxKeys)
-			_err = @_error( "ECACHEFULL" )
-			throw _err
+			# if replaceOldest then delete the oldest key
+			if(@options.replaceOldestKey)
+				oldestDate = Date.now()
+				oldestKey
+				for _key, _val of @data
+					if _val.d <= oldestDate
+						oldestDate = _val.d
+						oldestKey = _key
+				@del(oldestKey)
+			else
+				_err = @_error( "ECACHEFULL" )
+				throw _err
 
 		# force the data to string
 		if @options.forceString and not typeof value is "string"
@@ -632,6 +644,7 @@ module.exports = class NodeCache extends EventEmitter
 		oReturn =
 			t: livetime
 			v: if asClone then clone( value ) else value
+			d: now
 
 	# ## _unwrap
 	#

diff --git a/_src/test/mocha_test.coffee b/_src/test/mocha_test.coffee
@@ -23,6 +23,11 @@ localCacheMaxKeys = new nodeCache({
 	maxKeys: 2
 })
 
+localCacheReplaceOldestKey = new nodeCache({
+	maxKeys: 2,
+	replaceOldestKey: true
+})
+
 localCacheTTL = new nodeCache({
 	stdTTL: 0.3,
 	checkperiod: 0
@@ -381,7 +386,41 @@ describe "`#{pkg.name}@#{pkg.version}` on `node@#{process.version}`", () ->
 			return
 
 		return
-
+	describe "replaceOldest: replaces oldest key when set to true", () ->
+		before () ->
+			state =
+				key1: randomString(10)
+				key2: randomString(10)
+				key3: randomString(10)
+				value1: randomString(10)
+				value2: randomString(10)
+				value3: randomString(10)
+			return
+		it "remove oldest key to allow new cache when replaceOldest is true", (done) ->
+			setTimeout(()->
+				localCacheReplaceOldestKey.set(state.key1, state.value1)
+			, 100)
+			setTimeout(()-> 
+				localCacheReplaceOldestKey.set(state.key2, state.value2)
+			, 200)
+			setTimeout(()-> 
+				localCacheReplaceOldestKey.set(state.key3, state.value3)
+			, 300)
+			setTimeout(() ->
+				# oldest key key2 from previous test should be removed
+				should([state.key2, state.key3]).eql(localCacheReplaceOldestKey.keys())
+				done()
+				return
+			, 500)
+			return
+		it "throw error when maxSize if full and replaceOldest is false", () ->
+			localCacheReplaceOldestKey.options.replaceOldestKey = false
+			(()=> localCacheReplaceOldestKey.set(state.key2, state.value2).should.throw({
+				name: "ECACHEFULL"
+				message: "Cache max keys amount exceeded"
+			}))	
+			return
+		return 
 	describe "correct and incorrect key types", () ->
 		describe "number", () ->
 			before () ->

diff --git a/index.d.ts b/index.d.ts
@@ -207,6 +207,17 @@ declare namespace NodeCache {
 		 * @memberof Options
 		 */
 		maxKeys?: number;
+
+		/**
+		 * allow replacement of oldest key
+		 * 
+		 * If `true`: set operations won't throw an error when max amount of keys is reached. It'll delete the oldest key to create space
+		 * If `false`: set operation will throw an error when max amount of keys is reached.
+		 * 
+		 * @type {boolean}
+		 * @memberof Options
+		 */
+		 replaceOldestKey?: boolean
 	}
 
 	interface Stats {