在 nodejs 中创建大量 google pubsub 订阅者的推荐方法是什么？答案

【问题标题】：What's the recommended way of creating a large no of google pubsub subscribers in nodejs?在 nodejs 中创建大量 google pubsub 订阅者的推荐方法是什么？
【发布时间】：2020-05-19 11:33:01
【问题描述】：

我需要收听大约 40 个订阅（未来几天这个数字会增加）。

如果那时只有一个订阅，我会执行以下操作，

const subName = 'mysubscription'
const pubSubClient = new PubSub()
const startVidsubscription = pubSubClient.subscription(subName)
startVidsubscription.on('message', messageHandler)

const messageHandler = async(message) => {
// do stuff

}

但是，当我有数十个订阅时，我不能这样做。所以，我正在尝试以下内容：

// the name is the name of each subscription and the variable is the variable name in which I will be holding the subscription object. 
var subscriptionDetails = [
    {'name': 'M10057-sub-cam1Api', 'variable': 'M10057Subscription'},
    {'name': 'M10058-sub-cam1Api', 'variable': 'M10058Subscription'},
    {'name': 'M10059-sub-cam1Api', 'variable': 'M10059Subscription'},
]

for(const subscription of subscriptionDetails){
        var subscription.variable = pubSubClient.subscription(subscription.name)
        subscription.variable.on('message', messageHandler)
    }

但这给了我像Unexpected token, expected ; 这样的错误。

任何人请告诉我在nodejs中收听大量订阅的推荐方法

【问题讨论】：

标签： node.js google-cloud-platform publish-subscribe google-cloud-pubsub

【解决方案1】：

您的一般方法应该有效。您在将订阅对象分配给 subscription.variable 时可能会遇到问题，该对象已被定义为字符串。

类似下面的方法会起作用：

const {PubSub} = require('@google-cloud/pubsub');

const pubSubClient = new PubSub();
const messageHandler = async(message) => {
  // ... handle message ...
};

var subscriptionDetails = [
  {'name': 'M10057-sub-cam1Api'},
  {'name': 'M10058-sub-cam1Api'},
  {'name': 'M10059-sub-cam1Api'},
];

for (const subscription of subscriptionDetails) {
  subscription.variable = pubSubClient.subscription(subscription.name);
  subscription.variable.on('message', messageHandler);
}

然后您可以使用subscriptionDetails 中的variable 字段引用订阅对象。

如果您想引用名为“M10057Subscription”的订阅对象，您可以创建订阅对象的映射：

var subscriptionDetails = [
  {'name': 'M10057-sub-cam1Api', 'variable': 'M10057Subscription'},
  {'name': 'M10058-sub-cam1Api', 'variable': 'M10058Subscription'},
  {'name': 'M10059-sub-cam1Api', 'variable': 'M10059Subscription'},
];

var subscriptionObjects = {};

for (const subscription of subscriptionDetails) {
  subscriptionObjects[subscription.variable] = pubSubClient.subscription(subscription.name);
  subscriptionObjects[subscription.variable].on('message', messageHandler);
}

// subscriptionObjects['M10057Subscription'] is a subscription object

【讨论】：