打算原有source code中静态配置为主, 一些动态配置放在配置中心为辅. 写的这个util, 项目启动时拉取一次配置, cache在内存中, 当zookeeper中当前项目的配置发生变化时可主动推送, 更新cache.

/* ******************************************************************
 * dynamic config on the basis of zookeeper config center
 ****************************************************************** */
import ZK, { Event } from 'node-zookeeper-client'
import { promisify } from 'util'
import config from '../config'

const zookeeper = ZK.createClient(config.ZOO_KEEPER)
zookeeper.once('connected', getAllConfigs)
zookeeper.connect()

const getChildren = promisify(zookeeper.getChildren).bind(zookeeper)
const getData = promisify(zookeeper.getData).bind(zookeeper)
const path = `/config/${config.API_NAME}/${process.env.NODE_ENV}`

/**
 * local config cache, change on it is only triggered by config center
 */
const dynconfig = new Map<string, string>()

/**
 * fetch keys of all config nodes
 * start watching on config nodes creation or removal
 */
async function getAllConfigs() {
    const localKeys = [...dynconfig.keys()]

    const children = await getChildren(
        path,
        (event: Event) => {
            console.log('[config center] => [%s] %s', getAllConfigs.name, event.name)
            getAllConfigs()
        },
    )
    console.log('[config center] => below are latest config items fetched')
    await Promise.all(children.sort().map((key: string) => {
        const isNewKey = !localKeys.includes(key)
        return getConfig(key, isNewKey)
    }))

    // remove deleted config node from local config cache
    localKeys.forEach(key => {
        if (!children.includes(key)) {
            dynconfig.delete(key)
        }
    })
}

/**
 * fetch value of a config node
 * start watching on config node value update
 */
async function getConfig(key: string, addWatcher?: boolean) {
    const rawValue = await getData(
        `${path}/${key}`,
        // register a watcher only once
        !addWatcher ? undefined : (event: Event) => {
            console.log('[config center] => [%s] %s', getConfig.name, event.name)
            if (event.type !== Event.NODE_DELETED) {
                getConfig(key, true)
            }
        },
    )
    const value = rawValue.toString('utf8')
    console.log('    %s: %s', key, value)
    dynconfig.set(key, value)
}

export default dynconfig

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