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dns: coalesce identical concurrent lookup() requests #62599

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89 changes: 53 additions & 36 deletions lib/dns.js
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Original file line number Diff line number Diff line change
Expand Up @@ -22,14 +22,18 @@
'use strict';

const {
Array,
ArrayPrototypePush,
ObjectDefineProperties,
ObjectDefineProperty,
SafeMap,
Symbol,
} = primordials;

const cares = internalBinding('cares_wrap');
const { isIP } = require('internal/net');
const { customPromisifyArgs } = require('internal/util');
const { AsyncResource } = require('async_hooks');
const {
DNSException,
codes: {
Expand Down Expand Up @@ -105,36 +109,12 @@ const {

let promises = null; // Lazy loaded

function onlookup(err, addresses) {
if (err) {
return this.callback(new DNSException(err, 'getaddrinfo', this.hostname));
}
this.callback(null, addresses[0], this.family || isIP(addresses[0]));
if (this[kPerfHooksDnsLookupContext] && hasObserver('dns')) {
stopPerf(this, kPerfHooksDnsLookupContext, { detail: { addresses } });
}
}


function onlookupall(err, addresses) {
if (err) {
return this.callback(new DNSException(err, 'getaddrinfo', this.hostname));
}

const family = this.family;
for (let i = 0; i < addresses.length; i++) {
const addr = addresses[i];
addresses[i] = {
address: addr,
family: family || isIP(addr),
};
}

this.callback(null, addresses);
if (this[kPerfHooksDnsLookupContext] && hasObserver('dns')) {
stopPerf(this, kPerfHooksDnsLookupContext, { detail: { addresses } });
}
}
// Map of in-flight getaddrinfo requests for lookup coalescing.
// Key: `${hostname}\0${family}\0${hints}\0${order}`
// Value: Array<{ callback, all }>
// When multiple callers request the same lookup concurrently, only one
// getaddrinfo call is dispatched to the libuv threadpool.
const inflightLookups = new SafeMap();


// Easy DNS A/AAAA look up
Expand Down Expand Up @@ -213,12 +193,6 @@ function lookup(hostname, options, callback) {
return {};
}

const req = new GetAddrInfoReqWrap();
req.callback = callback;
req.family = family;
req.hostname = hostname;
req.oncomplete = all ? onlookupall : onlookup;

let order = DNS_ORDER_VERBATIM;

if (dnsOrder === 'ipv4first') {
Expand All @@ -227,10 +201,53 @@ function lookup(hostname, options, callback) {
order = DNS_ORDER_IPV6_FIRST;
}

const key = `${hostname}\0${family}\0${hints}\0${order}`;
const waiter = { callback: AsyncResource.bind(callback), all };

let inflight = inflightLookups.get(key);
if (inflight) {
// Piggyback on existing in-flight request.
ArrayPrototypePush(inflight, waiter);
return {};
}

// First request for this key - dispatch to libuv.
inflight = [waiter];
inflightLookups.set(key, inflight);

const req = new GetAddrInfoReqWrap();
req.family = family;
req.hostname = hostname;
req.oncomplete = function(errCode, addresses) {
inflightLookups.delete(key);
const waiters = inflight;
for (let i = 0; i < waiters.length; i++) {
const w = waiters[i];
if (errCode) {
w.callback(new DNSException(errCode, 'getaddrinfo', hostname));
} else if (w.all) {
const result = new Array(addresses.length);
for (let j = 0; j < addresses.length; j++) {
result[j] = {
address: addresses[j],
family: family || isIP(addresses[j]),
};
}
w.callback(null, result);
} else {
w.callback(null, addresses[0], family || isIP(addresses[0]));
}
}
if (this[kPerfHooksDnsLookupContext] && hasObserver('dns')) {
stopPerf(this, kPerfHooksDnsLookupContext, { detail: { addresses } });
}
};

const err = cares.getaddrinfo(
req, hostname, family, hints, order,
);
if (err) {
inflightLookups.delete(key);
process.nextTick(callback, new DNSException(err, 'getaddrinfo', hostname));
return {};
}
Expand Down
128 changes: 65 additions & 63 deletions lib/internal/dns/promises.js
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Open in desktop
Original file line number Diff line number Diff line change
@@ -1,9 +1,13 @@
'use strict';
const {
Array,
ArrayPrototypeMap,
FunctionPrototypeCall,
ObjectDefineProperty,
Promise,
PromiseReject,
PromiseResolve,
SafeMap,
Symbol,
} = primordials;

Expand Down Expand Up @@ -82,41 +86,14 @@ const {
stopPerf,
} = require('internal/perf/observe');

function onlookup(err, addresses) {
if (err) {
this.reject(new DNSException(err, 'getaddrinfo', this.hostname));
return;
}

const family = this.family || isIP(addresses[0]);
this.resolve({ address: addresses[0], family });
if (this[kPerfHooksDnsLookupContext] && hasObserver('dns')) {
stopPerf(this, kPerfHooksDnsLookupContext, { detail: { addresses } });
}
}

function onlookupall(err, addresses) {
if (err) {
this.reject(new DNSException(err, 'getaddrinfo', this.hostname));
return;
}

const family = this.family;

for (let i = 0; i < addresses.length; i++) {
const address = addresses[i];

addresses[i] = {
address,
family: family || isIP(addresses[i]),
};
}

this.resolve(addresses);
if (this[kPerfHooksDnsLookupContext] && hasObserver('dns')) {
stopPerf(this, kPerfHooksDnsLookupContext, { detail: { addresses } });
}
}
// Map of in-flight getaddrinfo requests for lookup coalescing.
// Key: `${hostname}\0${family}\0${hints}\0${order}`
// Value: Promise<{ err: number|null, addresses: string[]|null }>
// When multiple callers request the same lookup concurrently, only one
// getaddrinfo call is dispatched to the libuv threadpool. All callers
// share the result, avoiding threadpool starvation under sustained DNS
// failure where each getaddrinfo blocks for many seconds.
const inflightLookups = new SafeMap();

/**
* Creates a promise that resolves with the IP address of the given hostname.
Expand All @@ -132,41 +109,48 @@ function onlookupall(err, addresses) {
* @property {0 | 4 | 6} family - The IP address type. 4 for IPv4 or 6 for IPv6, or 0 (for both).
*/
function createLookupPromise(family, hostname, all, hints, dnsOrder) {
return new Promise((resolve, reject) => {
if (!hostname) {
reject(new ERR_INVALID_ARG_VALUE('hostname', hostname,
'must be a non-empty string'));
return;
}
if (!hostname) {
return PromiseReject(
new ERR_INVALID_ARG_VALUE('hostname', hostname,
'must be a non-empty string'));
}

const matchedFamily = isIP(hostname);
const matchedFamily = isIP(hostname);
if (matchedFamily !== 0) {
const result = { address: hostname, family: matchedFamily };
return PromiseResolve(all ? [result] : result);
}

if (matchedFamily !== 0) {
const result = { address: hostname, family: matchedFamily };
resolve(all ? [result] : result);
return;
}
let order = DNS_ORDER_VERBATIM;
if (dnsOrder === 'ipv4first') {
order = DNS_ORDER_IPV4_FIRST;
} else if (dnsOrder === 'ipv6first') {
order = DNS_ORDER_IPV6_FIRST;
}

const req = new GetAddrInfoReqWrap();
const key = `${hostname}\0${family}\0${hints}\0${order}`;

let rawPromise = inflightLookups.get(key);
if (!rawPromise) {
let resolveRaw;
rawPromise = new Promise((resolve) => { resolveRaw = resolve; });
inflightLookups.set(key, rawPromise);

const req = new GetAddrInfoReqWrap();
req.family = family;
req.hostname = hostname;
req.oncomplete = all ? onlookupall : onlookup;
req.resolve = resolve;
req.reject = reject;

let order = DNS_ORDER_VERBATIM;

if (dnsOrder === 'ipv4first') {
order = DNS_ORDER_IPV4_FIRST;
} else if (dnsOrder === 'ipv6first') {
order = DNS_ORDER_IPV6_FIRST;
}

const err = getaddrinfo(req, hostname, family, hints, order);
req.oncomplete = function(errCode, addresses) {
inflightLookups.delete(key);
resolveRaw({ err: errCode, addresses });
if (this[kPerfHooksDnsLookupContext] && hasObserver('dns')) {
stopPerf(this, kPerfHooksDnsLookupContext, { detail: { addresses } });
}
};

if (err) {
reject(new DNSException(err, 'getaddrinfo', hostname));
const errCode = getaddrinfo(req, hostname, family, hints, order);
if (errCode) {
inflightLookups.delete(key);
resolveRaw({ err: errCode, addresses: null });
} else if (hasObserver('dns')) {
const detail = {
hostname,
Expand All @@ -177,6 +161,24 @@ function createLookupPromise(family, hostname, all, hints, dnsOrder) {
};
startPerf(req, kPerfHooksDnsLookupContext, { type: 'dns', name: 'lookup', detail });
}
}

// Each caller post-processes the shared raw result independently.
return rawPromise.then(({ err, addresses }) => {
if (err) {
throw new DNSException(err, 'getaddrinfo', hostname);
}
if (all) {
const result = new Array(addresses.length);
for (let i = 0; i < addresses.length; i++) {
result[i] = {
address: addresses[i],
family: family || isIP(addresses[i]),
};
}
return result;
}
return { address: addresses[0], family: family || isIP(addresses[0]) };
});
}

Expand Down
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