Check mongoose connection state without creating new connection

I have some tests - namely Supertest - that load my Express app. This app creates a Mongoose connection. I would like to know how to check the status of that connection from within my test.

In app.js

mongoose.connect(...)

In test.js

console.log(mongoose.connection.readyState);

How to access the app.js connection? If I connect using the same parameters in test.js will that create a new connection or look for existing one?

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最佳答案

Since the mongoose module exports a singleton object, you don't have to connect in your test.js to check the state of the connection:

// test.js
require('./app.js'); // which executes 'mongoose.connect()'


var mongoose = require('mongoose');
console.log(mongoose.connection.readyState);

ready states being:

  • 0: disconnected
  • 1: connected
  • 2: connecting
  • 3: disconnecting
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I use this for my Express Server mongoDB status, where I use the express-healthcheck middleware

// Define server status
const mongoose = require('mongoose');
const serverStatus = () => {
return {
state: 'up',
dbState: mongoose.STATES[mongoose.connection.readyState]
}
};
//  Plug into middleware.
api.use('/api/uptime', require('express-healthcheck')({
healthy: serverStatus
}));

Gives this in a Postman request when the DB is connected.

{
"state": "up",
"dbState": "connected"
}

Gives this response when the database was shutdown.

{
"state": "up",
"dbState": "disconnected"
}

(The "up" in the responses represent my Express Server status)

Easy to read (no numbers to interpret)

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As stated before "readyState" is good. "ping" is also good admin utility for doing so as well. It will return { ok: 1 } if it can accept commands.

const mongoose = require('mongoose')


// From where ever your making your connection
const connection = await mongoose.createConnection(
CONNECT_URI,
CONNECT_OPTS
)


async function connectionIsUp(): Promise<boolean> {
try {
const adminUtil = connection.db.admin()


const result = await adminUtil.ping()


console.log('result: ', result) // { ok: 1 }
return !!result?.ok === 1
} catch(err) {
return false
}
}

Or if you you want it short.

async function connectionIsUp(): Promise<boolean> {
try {
return await connection.db.admin().ping().then(res => !!res?.ok === 1)
} catch (err) {
return false
}
}
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var dbState = [{
value: 0,
label: "disconnected"
},
{
value: 1,
label: "connected"
},
{
value: 2,
label: "connecting"
},
{
value: 3,
label: "disconnecting"
}];


mongoose.connect(CONNECTIONSTRING, {
useNewUrlParser: true
},
() => {
const state = Number(mongoose.connection.readyState);
console.log(dbState.find(f => f.value == state).label, "to db"); // connected to db
});

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