add custom linkedlist-impl

packages/unleash-api/lib/client-metrics/list.js

@@ -0,0 +1,132 @@
+'use strict';
+
+const { EventEmitter } = require('events');
+
+class Node {
+    constructor (value) {
+        this.value = value;
+        this.next = null;
+    }
+
+    link (next) {
+        this.next = next;
+        next.prev = this;
+    }
+}
+
+
+/*
+    * linked list
+    * ranged list, assumes start to end(tail) is a known order
+        * remove() is only implemented in reverse order for the usecase
+    * emits events on eviction
+*/
+module.exports = class List extends EventEmitter {
+    constructor () {
+        super();
+        this.start = null;
+        this.tail = null;
+    }
+
+    add (obj) {
+        const node = new Node(obj);
+        if (this.tail) {
+            this.tail.link(node);
+            this.tail = node;
+        } else {
+            this.start = node;
+            this.tail = node;
+        }
+        return node;
+    }
+
+    iterate (fn) {
+        if (!this.start) {
+            return;
+        }
+        let cursor = this.start;
+        while (cursor) {
+            const result = fn(cursor);
+            if (result === false) {
+                cursor = null;
+            } else {
+                cursor = cursor.next;
+            }
+        }
+    }
+
+    iterateReverse (fn) {
+        if (!this.tail) {
+            return;
+        }
+        let cursor = this.tail;
+        while (cursor) {
+            const result = fn(cursor);
+            if (result === false) {
+                cursor = null;
+            } else {
+                cursor = cursor.prev;
+            }
+        }
+    }
+
+    reverseRemoveUntilTrue (fn) {
+        if (!this.tail) {
+            return;
+        }
+
+        let cursor = this.tail;
+        while (cursor) {
+            const result = fn(cursor);
+            if (result === false && cursor === this.start) {
+                // whole list is removed
+                this.emit('evicted', cursor.value);
+                this.start = null;
+                this.tail  = null;
+                // stop iteration
+                cursor = null;
+            } else if (result === true) {
+                // when TRUE, set match as new tail
+                if (cursor !== this.tail) {
+                    this.tail = cursor;
+                    cursor.next = null;
+                }
+                // stop iteration
+                cursor = null;
+            } else {
+                // evicted
+                this.emit('evicted', cursor.value);
+                // iterate to next
+                cursor = cursor.prev;
+            }
+        }
+    }
+
+    toArray () {
+        const result = [];
+
+        if (this.start) {
+            let cursor = this.start;
+            while (cursor) {
+                result.push(cursor.value);
+                cursor = cursor.next;
+            }
+        }
+
+        return result;
+    }
+
+    toArrayReverse () {
+        const result = [];
+
+        if (this.tail) {
+            let cursor = this.tail;
+            while (cursor) {
+                result.push(cursor.value);
+                cursor = cursor.prev;
+            }
+        }
+
+        return result;
+    }
+};

packages/unleash-api/lib/client-metrics/list.test.js

@@ -0,0 +1,107 @@
+'use strict';
+
+const test = require('ava');
+const List = require('./list');
+
+function getList () {
+    const list = new List();
+    list.add(1);
+    list.add(2);
+    list.add(3);
+    list.add(4);
+    list.add(5);
+    list.add(6);
+    list.add(7);
+    return list;
+}
+
+test('should emit "evicted" events for objects leaving list', (t) => {
+    const list = getList();
+    const evictedList = [];
+    list.on('evicted', (value) => {
+        evictedList.push(value);
+    });
+
+    t.true(evictedList.length === 0);
+
+    list.reverseRemoveUntilTrue(({ value }) => {
+        if (value === 4) {
+            return true;
+        }
+        return false;
+    });
+
+    t.true(evictedList.length === 3);
+
+    list.reverseRemoveUntilTrue(() => false);
+
+    t.true(evictedList.length === 7);
+
+    list.add(1);
+    list.reverseRemoveUntilTrue(() => false);
+
+    t.true(evictedList.length === 8);
+});
+
+test('list should be able remove until given value', (t) => {
+    const list = getList();
+
+    t.true(list.toArray().length === 7);
+
+    list.reverseRemoveUntilTrue(({ value }) => value === 4);
+    t.true(list.toArray().length === 4);
+
+    list.reverseRemoveUntilTrue(({ value }) => value === 3);
+    t.true(list.toArray().length === 3);
+
+    list.reverseRemoveUntilTrue(({ value }) => value === 3);
+    t.true(list.toArray().length === 3);
+});
+
+test('list can be cleared and re-add entries', (t) => {
+    const list = getList();
+
+    list.add(8);
+    list.add(9);
+
+    t.true(list.toArray().length === 9);
+
+    list.reverseRemoveUntilTrue(() => false);
+
+    t.true(list.toArray().length === 0);
+
+    list.add(1);
+    list.add(2);
+    list.add(3);
+
+    t.true(list.toArray().length === 3);
+});
+
+
+test('should iterate', (t) => {
+    const list = getList();
+
+    let iterateCount = 0;
+    list.iterate(({ value }) => {
+        iterateCount++;
+        if (value === 4) {
+            return false;
+        }
+        return true;
+    });
+    t.true(iterateCount === 4);
+});
+
+test('should reverse iterate', (t) => {
+    const list = getList();
+
+    let iterateCount = 0;
+    list.iterateReverse(({ value }) => {
+        iterateCount++;
+        if (value === 3) {
+            return false;
+        }
+        return true;
+    });
+    t.true(iterateCount === 5);
+});

packages/unleash-api/lib/client-metrics/ttl-list.js

@@ -1,47 +1,44 @@
 'use strict';
 
 const { EventEmitter } = require('events');
-const yallist = require('yallist');
+const List = require('./list');
 const moment = require('moment');
 
-// this list must have entires with sorted ttl range
-module.exports = class TTLList extends EventEmitter {
-    constructor () {
+// this list must have entries with sorted ttl range
+module.exports = class FIFOTTLList extends EventEmitter {
+    constructor ({
+        interval = 1000,
+        expireAmount = 1,
+        expireType = 'hours',
+    } = {}) {
         super();
-        this.cache = yallist.create();
-        setInterval(() => {
+        this.expireAmount = expireAmount;
+        this.expireType = expireType;
+
+        this.list = new List();
+
+        this.list.on('evicted', ({ value, ttl }) => {
+            this.emit('expire', value, ttl);
+        });
+
+        this.timer = setInterval(() => {
             this.timedCheck();
-        }, 1000);
+        }, interval);
     }
 
-    expire (entry) {
-        this.emit('expire', entry.value);
-    }
-
-    add (value, timestamp) {
-        const ttl = moment(timestamp).add(1, 'hour');
-        this.cache.push({ ttl, value });
+    add (value, timestamp = new Date()) {
+        const ttl = moment(timestamp).add(this.expireAmount, this.expireType);
+        this.list.add({ ttl, value });
     }
 
     timedCheck () {
         const now = moment(new Date());
-        // find index to remove
-        let done = false;
-        // TODO: might use internal linkedlist
-        this.cache.forEachReverse((entry, index) => {
-            if (done) {
-                return;
-            } else if (now.isBefore(entry.ttl)) {
-                // When we hit a valid ttl, remove next items in list (iteration is reversed)
-                this.cache = this.cache.slice(0, index + 1);
-                done = true;
-            } else if (index === 0) {
-                this.expire(entry);
-                // if rest of list has timed out, let it DIE!
-                this.cache = yallist.create(); // empty=
-            } else {
-                this.expire(entry);
+        this.list.reverseRemoveUntilTrue(({ value }) => now.isBefore(value.ttl));
     }
-        });
+
+    destroy () {
+        clearTimeout(this.timer);
+        delete this.timer;
+        this.list = null;
     }
 };

packages/unleash-api/lib/client-metrics/ttl-list.test.js

@@ -0,0 +1,63 @@
+'use strict';
+
+const test = require('ava');
+const TTLList = require('./ttl-list');
+const moment = require('moment');
+
+test.cb('should emit expire', (t) => {
+    const list = new TTLList({
+        interval: 20,
+        expireAmount: 10,
+        expireType: 'milliseconds',
+    });
+
+    list.on('expire', (entry) => {
+        list.destroy();
+        t.true(entry.n === 1);
+        t.end();
+    });
+
+    list.add({ n: 1 });
+});
+
+test.cb('should slice off list', (t) => {
+    const list = new TTLList({
+        interval: 10,
+        expireAmount: 10,
+        expireType: 'milliseconds',
+    });
+
+    // console.time('4');
+    list.add({ n: '4' }, moment().add(300, 'milliseconds'));
+
+    // console.time('3');
+    list.add({ n: '3' }, moment().add(200, 'milliseconds'));
+
+    // console.time('2');
+    list.add({ n: '2' }, moment().add(50, 'milliseconds'));
+
+    // console.time('1');
+    list.add({ n: '1' }, moment().add(1, 'milliseconds'));
+
+    const expired = [];
+
+    list.on('expire', (entry) => {
+        // console.timeEnd(entry.n);
+        expired.push(entry);
+    });
+
+    setTimeout(() => {
+        t.true(expired.length === 1);
+    }, 30);
+    setTimeout(() => {
+        t.true(expired.length === 2);
+    }, 71);
+    setTimeout(() => {
+        t.true(expired.length === 3);
+    }, 221);
+    setTimeout(() => {
+        t.true(expired.length === 4);
+        list.destroy();
+        t.end();
+    }, 330);
+});

packages/unleash-api/package.json

@@ -65,6 +65,7 @@
   },
   "devDependencies": {
     "bluebird": "^3.4.6",
+    "ava": "^0.16.0",
     "coveralls": "^2.11.12",
     "istanbul": "^0.4.5",
     "mocha": "^3.0.2",