querySrv ENODATA checking a Mongo SRV record using Node

The Mongo driver prefix the "hostname" with "_mongodb._tcp.".

Reference https://github.com/mongodb/node-mongodb-native/blob/e69d9925713ede3bd80d7d23a6df60c6dd4542ef/src/connection_string.ts#L78

function getMongoSrvHostnameFromDbConnectionString(dbConnectionString: string) {

const startIndex = dbConnectionString.indexOf('@') + 1;

const endIndex = dbConnectionString.indexOf('/', startIndex);

const dbHostname = dbConnectionString.substring(startIndex, endIndex);

// Ref: https://github.com/mongodb/node-mongodb-native/blob/e69d9925713ede3bd80d7d23a6df60c6dd4542ef/src/connection_string.ts#L78

return `_mongodb._tcp.${dbHostname}`;

}

async function resolveSrvHostnamesOrError(

hostname: string,

): Promise<string[] | string> {

const resolveSrv = util.promisify(dns.resolveSrv);

const lookup = util.promisify(dns.lookup);

let ipsOrError: string[] | string = null;

try {

const resolvedHostnames = await resolveSrv(hostname);

const resolvedAddresses = await Promise.all(

resolvedHostnames.map(

async (resolvedHostname) => await lookup(resolvedHostname.name),

),

);

return await Promise.all(

resolvedAddresses.map(

async (resolvedAddress) => (await resolvedAddress).address,

),

);

} catch (err) {

console.log(err);

const e: Error = err;

ipsOrError = e.message;

return ipsOrError;

}

}