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feat: support more loadbalance algorithm (#7)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,40 @@ | ||
| 'use strict'; | ||
|
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| const Base = require('sdk-base'); | ||
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| class LoadBalancer extends Base { | ||
| constructor(addressGroup) { | ||
| super(); | ||
| this.addressGroup = addressGroup; | ||
| this.reset(); | ||
| this.ready(true); | ||
| } | ||
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| get size() { | ||
| return this.addressGroup._choosedSize; | ||
| } | ||
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| get addressList() { | ||
| return this.addressGroup.addressList; | ||
| } | ||
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| select(request) { | ||
| if (this.size === 0) return null; | ||
| if (this.size === 1) return this.addressList[0]; | ||
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| return this._doSelect(request, this.addressList); | ||
| } | ||
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| reset() {} | ||
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| /* istanbul ignore next */ | ||
| _doSelect() { | ||
| throw new Error('not implement'); | ||
| } | ||
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| getWeight(address) { | ||
| return this.addressGroup.getWeight(address); | ||
| } | ||
| } | ||
|
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| module.exports = LoadBalancer; |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,66 @@ | ||
| 'use strict'; | ||
|
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| const utils = require('../utils'); | ||
| const LoadBalancer = require('./base'); | ||
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| const NUM = 128; | ||
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| class ConsistentHashLoadBalancer extends LoadBalancer { | ||
| reset() { | ||
| this._virtualNodes = new Map(); | ||
| if (this.addressList) { | ||
| for (const address of this.addressList) { | ||
| for (let i = 0; i < NUM / 4; i++) { | ||
| const digest = this._messageDigest(`${address.host}${i}`); | ||
| for (let h = 0; h < 4; h++) { | ||
| const m = this._hash(digest, h); | ||
| this._virtualNodes.set(m, address); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| this._sortKeys = Array.from(this._virtualNodes.keys()).sort(); | ||
| } | ||
|
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| /* eslint-disable no-bitwise */ | ||
| _hash(digest, index) { | ||
| const f = ((digest[3 + index * 4] & 0xFF) << 24) | | ||
| ((digest[2 + index * 4] & 0xFF) << 16) | | ||
| ((digest[1 + index * 4] & 0xFF) << 8) | | ||
| (digest[index * 4] & 0xFF); | ||
| return f & 0xFFFFFFFF; | ||
| } | ||
| /* eslint-enable no-bitwise */ | ||
|
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| _messageDigest(value) { | ||
| return utils.md5(value); | ||
| } | ||
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| _selectForKey(hash) { | ||
| const len = this._sortKeys.length; | ||
| let key = this._sortKeys[0]; | ||
| if (this._sortKeys[len - 1] >= hash) { | ||
| for (let i = len - 1; i >= 0; i--) { | ||
| if (this._sortKeys[i] < hash) { | ||
| key = this._sortKeys[i + 1]; | ||
| break; | ||
| } | ||
| } | ||
| } | ||
| return this._virtualNodes.get(key); | ||
| } | ||
|
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| _buildKeyOfHash(request) { | ||
| const args = request.args; | ||
| if (!args.length) return ''; | ||
| return JSON.stringify(args[0]); | ||
| } | ||
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| _doSelect(request) { | ||
| const key = this._buildKeyOfHash(request); | ||
| const digest = this._messageDigest(key); | ||
| return this._selectForKey(this._hash(digest, 0)); | ||
| } | ||
| } | ||
|
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| module.exports = ConsistentHashLoadBalancer; |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,24 @@ | ||
| 'use strict'; | ||
|
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| const assert = require('assert'); | ||
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| const buildinLoadBalancers = { | ||
| get random() { | ||
| return require('./random'); | ||
| }, | ||
| get roundRobin() { | ||
| return require('./weight_rr'); | ||
| }, | ||
| get consistentHash() { | ||
| return require('./consistent_hash'); | ||
| }, | ||
| }; | ||
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| module.exports = addressGroup => { | ||
| let loadbalancerClass = addressGroup.loadbalancerClass; | ||
| if (typeof loadbalancerClass === 'string') { | ||
| loadbalancerClass = buildinLoadBalancers[loadbalancerClass]; | ||
| } | ||
| assert(typeof loadbalancerClass === 'function', `loadbalancerClass:${addressGroup.loadbalancerClass} invalid`); | ||
| return new loadbalancerClass(addressGroup); | ||
| }; |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,39 @@ | ||
| 'use strict'; | ||
|
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| const utility = require('utility'); | ||
| const LoadBalancer = require('./base'); | ||
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| // 负载均衡随机算法:全部列表按权重随机选择 | ||
| class RandomLoadBalancer extends LoadBalancer { | ||
| _doSelect(request, addressList) { | ||
| const len = addressList.length; | ||
| let totalWeight = 0; | ||
| let isWeightSame = true; | ||
| let address; | ||
| for (let i = 0; i < len; i++) { | ||
| const weigit = this.getWeight(addressList[i]); | ||
| totalWeight += weigit; | ||
| if (isWeightSame && i > 0 && weigit !== this.getWeight(addressList[i - 1])) { | ||
| isWeightSame = false; | ||
| } | ||
| } | ||
| if (totalWeight > 0 && !isWeightSame) { | ||
| // 如果权重不相同且权重大于0则按总权重数随机 | ||
| let offset = utility.random(totalWeight); | ||
| for (let i = 0; i < len; i++) { | ||
| // 并确定随机值落在哪个片断上 | ||
| offset -= this.getWeight(addressList[i]); | ||
| if (offset < 0) { | ||
| address = addressList[i]; | ||
| break; | ||
| } | ||
| } | ||
| } else { | ||
| const index = utility.random(len); // math.randomInt(len); | ||
| address = addressList[index]; | ||
| } | ||
| return address; | ||
| } | ||
| } | ||
|
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| module.exports = RandomLoadBalancer; |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,38 @@ | ||
| 'use strict'; | ||
|
|
||
| const utility = require('utility'); | ||
| const LoadBalancer = require('./base'); | ||
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| const DEFAULT_WEIGHT = 100; | ||
|
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| // 带权重的 Round Robin 算法 | ||
| class WeightRoundRobinLoadBalancer extends LoadBalancer { | ||
| reset() { | ||
| this._offset = utility.random(this.size); | ||
| } | ||
|
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| _rr(request, addressList) { | ||
| const address = addressList[this._offset]; | ||
| this._offset = (this._offset + 1) % this.size; | ||
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| const weight = this.getWeight(address); | ||
| if (weight === DEFAULT_WEIGHT) return address; | ||
| if (weight === 0) return null; | ||
|
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| const randNum = utility.random(DEFAULT_WEIGHT); | ||
| return weight >= randNum ? address : null; | ||
| } | ||
|
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| _doSelect(request, addressList) { | ||
| let address; | ||
| let count = this.size; | ||
| while (count--) { | ||
| address = this._rr(request, addressList); | ||
| if (address) return address; | ||
| } | ||
| // 直接返回兜底 | ||
| return addressList[this._offset]; | ||
| } | ||
| } | ||
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| module.exports = WeightRoundRobinLoadBalancer; |
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