So I have this async function where I make multiple calls to NodeJS's DNS Api. The first two calls return data but because of the third one, the catch block triggers and I don't get the data from the first two.
As it all depends on the type of query(netflix.com), some of the await operations might throw an error because of no data. But what I want is I want to get data from the other calls even if there are errors from some of them.
Here's the code:
const dnsResolve = async () => {
const query = 'netflix.com';
try{
const aRecord = await dns.resolve4(query);
const aaaaRecord = await dns.resolve6(query);
const cnameRecord = await dns.resolveCname(query);
console.log(aRecord);
console.log(aaaaRecord);
console.log(cnameRecord);
}catch(err) {
console.log(err);
}
}
dnsResolve();
The above code returns
Error: queryCname ENODATA netflix.com
at QueryReqWrap.onresolve [as oncomplete] (internal/dns/promises.js:167:17) {
errno: undefined,
code: 'ENODATA',
syscall: 'queryCname',
hostname: 'netflix.com'
}
Individual outputs from the first two queries:
aRecord: [
{ address: '51.73.1.12' },
{ address: '55.83.62.128' },
{ address: '12.12.82.118' }
]
aaaaRecord: [
{ address: '2406:da200:ff00::222c0:598a' },
{ address: '24206:da00:ff00::22c2:44203' },
{ address: '2406:da0e0:ff00::36de2:41fd' }
]
How I want to display the data:
[
{ address: '51.73.1.12' },
{ address: '55.83.62.128' },
{ address: '12.12.82.118' },
{ address: '2406:da200:ff00::222c0:598a' },
{ address: '24206:da00:ff00::22c2:44203' },
{ address: '2406:da0e0:ff00::36de2:41fd' },
{ NO CNAME RECORDS }
]
Please note that there will be around 6 calls to the DNS API. It cannot be determined which one will trigger an error because of no data. It totally depends on the query.
This is the very use case Promise.allSettled is for:
const results = await Promise.allSettled([
dns.resolve4(query),
dns.resolve6(query),
dns.resolveCname(query),
]);
for (const {status, value, reason} of results) {
if (status === "fulfilled") {
// Promise was fulfilled, use `value`...
} else {
// Promise was rejected, see `reason` for why...
}
}
Or if you only want the successful results:
const results = await Promise.allSettled([
dns.resolve4(query),
dns.resolve6(query),
dns.resolveCname(query),
]);
const values = results.filter(({status}) => status === "fulfilled")
.map(({value}) => value);
// ...use `values`...