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chore: Resolve DNS TXT record to instance name. Part of DNS Config.
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‎src/dns-lookup.ts‎

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// Copyright 2025 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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import dns from 'node:dns';
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import {CloudSQLConnectorError} from './errors';
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export async function resolveTxtRecord(name: string): Promise<string> {
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return new Promise((resolve, reject) => {
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dns.resolveTxt(name, (err, addresses) => {
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if (err) {
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reject(
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new CloudSQLConnectorError({
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code: 'EDOMAINNAMELOOKUPERROR',
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message: 'Error looking up TXT record for domain ' + name,
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errors: [err],
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})
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);
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return;
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}
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if (!addresses || addresses.length === 0) {
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reject(
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new CloudSQLConnectorError({
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code: 'EDOMAINNAMELOOKUPFAILED',
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message: 'No records returned for domain ' + name,
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})
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);
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return;
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}
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// Each result may be split into multiple strings. Join the strings.
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const joinedAddresses = addresses.map(strs => strs.join(''));
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// Sort the results alphabetically for consistency,
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joinedAddresses.sort((a, b) => a.localeCompare(b));
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// Return the first result.
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resolve(joinedAddresses[0]);
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});
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});
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}

‎src/parse-instance-connection-name.ts‎

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@@ -14,6 +14,29 @@
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import {InstanceConnectionInfo} from './instance-connection-info';
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import {CloudSQLConnectorError} from './errors';
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import {resolveTxtRecord} from './dns-lookup';
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export async function resolveInstanceName(
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name: string | undefined
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): Promise<InstanceConnectionInfo> {
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if (!name) {
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throw new CloudSQLConnectorError({
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message:
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'Missing instance connection name, expected: "PROJECT:REGION:INSTANCE"',
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code: 'ENOCONNECTIONNAME',
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});
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} else if (isInstanceConnectionName(name)) {
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return parseInstanceConnectionName(name);
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} else if (isValidDomainName(name)) {
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return await resolveDomainName(name);
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} else {
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throw new CloudSQLConnectorError({
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message:
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'Malformed Instance connection name, expected an instance connection name in the form "PROJECT:REGION:INSTANCE" or a valid domain name',
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code: 'EBADCONNECTIONNAME',
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});
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}
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}
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const connectionNameRegex =
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/^(?<projectId>[^:]+(:[^:]+)?):(?<regionId>[^:]+):(?<instanceId>[^:]+)$/;
@@ -33,6 +56,26 @@ export function isInstanceConnectionName(name: string): boolean {
3356
return Boolean(matches);
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}
3558

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export async function resolveDomainName(
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name: string
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): Promise<InstanceConnectionInfo> {
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const icn = await resolveTxtRecord(name);
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if (!isInstanceConnectionName(icn)) {
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throw new CloudSQLConnectorError({
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message:
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'Malformed instance connection name returned for domain ' +
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name +
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' : ' +
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icn,
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code: 'EBADDOMAINCONNECTIONNAME',
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});
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}
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const info = parseInstanceConnectionName(icn);
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info.domainName = name;
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return info;
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}
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3679
export function parseInstanceConnectionName(
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instanceConnectionName: string | undefined
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): InstanceConnectionInfo {

‎test/dns-lookup.ts‎

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// Copyright 2025 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
10+
// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
13+
// limitations under the License.
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import t from 'tap';
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t.test('lookup dns with mock responses', async t => {
18+
const {resolveTxtRecord} = t.mockRequire('../src/dns-lookup.ts', {
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'node:dns': {
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resolveTxt: (name, callback) => {
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switch (name) {
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case 'db.example.com':
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callback(null, [['my-project:region-1:instance']]);
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return;
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case 'multiple.example.com':
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callback(null, [
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['my-project:region-1:instance'],
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['another-project:region-1:instance'],
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]);
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return;
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case 'split.example.com':
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callback(null, [['my-project:', 'region-1:instance']]);
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return;
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case 'empty.example.com':
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callback(null, []);
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return;
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default:
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callback(new Error('not found'), null);
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return;
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}
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},
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},
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});
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t.same(
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await resolveTxtRecord('db.example.com'),
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'my-project:region-1:instance',
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'valid domain name'
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);
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t.same(
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await resolveTxtRecord('split.example.com'),
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'my-project:region-1:instance',
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'valid domain name'
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);
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t.same(
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await resolveTxtRecord('multiple.example.com'),
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'another-project:region-1:instance',
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'valid domain name'
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);
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t.rejects(
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async () => await resolveTxtRecord('not-found.example.com'),
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{code: 'EDOMAINNAMELOOKUPERROR'},
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'should throw type error if an extra item is provided'
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);
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t.rejects(
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async () => await resolveTxtRecord('empty.example.com'),
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{code: 'EDOMAINNAMELOOKUPFAILED'},
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'should throw type error if an extra item is provided'
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);
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});
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72+
t.test('lookup dns with real responses', async t => {
73+
const {resolveTxtRecord} = t.mockRequire('../src/dns-lookup.ts', {});
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t.same(
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await resolveTxtRecord('valid-san-test.csqlconnectortest.com'),
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'cloud-sql-connector-testing:us-central1:postgres-customer-cas-test',
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'valid domain name'
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);
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});

‎test/parse-instance-connection-name.ts‎

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Original file line numberDiff line numberDiff line change
@@ -18,6 +18,7 @@ import {
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isValidDomainName,
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isInstanceConnectionName,
2020
} from '../src/parse-instance-connection-name';
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import {CloudSQLConnectorError} from '../src/errors';
2122

2223
t.throws(
2324
() => parseInstanceConnectionName(undefined),
@@ -92,6 +93,7 @@ t.same(
9293
);
9394

9495
t.same(isValidDomainName('project.example.com'), true, 'valid domain name');
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t.same(isValidDomainName('project.example.com.'), true, 'valid domain name');
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9698
t.same(isValidDomainName('google.com:PROJECT'), false, 'invalid domain name');
9799

@@ -106,3 +108,121 @@ t.same(
106108
false,
107109
'should validate domain name'
108110
);
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t.test('resolveDomainName Mock DNS', async () => {
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// mocks crypto module so that it can return a deterministic result
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// and set a standard, fast static value for cert refresh interval
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const {resolveDomainName} = t.mockRequire(
116+
'../src/parse-instance-connection-name',
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{
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'../src/dns-lookup': {
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resolveTxtRecord: async name => {
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switch (name) {
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case 'db.example.com':
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return 'my-project:region-1:my-instance';
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case 'bad.example.com':
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return 'bad-instance-name';
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default:
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throw new CloudSQLConnectorError({
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code: 'EDOMAINNAMELOOKUPERROR',
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message: 'Error looking up TXT record for domain ' + name,
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});
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}
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},
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},
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}
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);
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t.same(
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await resolveDomainName('db.example.com'),
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{
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projectId: 'my-project',
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regionId: 'region-1',
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instanceId: 'my-instance',
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domainName: 'db.example.com',
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},
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'should validate domain name'
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);
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t.rejects(
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async () => await resolveDomainName('bad.example.com'),
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{code: 'EBADDOMAINCONNECTIONNAME'},
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'should throw type error if an extra item is provided'
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);
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t.rejects(
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async () => await resolveDomainName('no-record.example.com'),
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{code: 'EDOMAINNAMELOOKUPERROR'},
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'should throw type error if an extra item is provided'
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);
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});
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t.test('resolveInstanceName Mock DNS', async () => {
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// mocks crypto module so that it can return a deterministic result
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// and set a standard, fast static value for cert refresh interval
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const {resolveInstanceName} = t.mockRequire(
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'../src/parse-instance-connection-name',
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{
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'../src/dns-lookup': {
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resolveTxtRecord: async name => {
168+
switch (name) {
169+
case 'db.example.com':
170+
return 'my-project:region-1:my-instance';
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case 'bad.example.com':
172+
return 'bad-instance-name';
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default:
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throw new CloudSQLConnectorError({
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code: 'EDOMAINNAMELOOKUPERROR',
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message: 'Error looking up TXT record for domain ' + name,
177+
});
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}
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},
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},
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}
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);
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184+
t.same(
185+
await resolveInstanceName('db.example.com'),
186+
{
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projectId: 'my-project',
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regionId: 'region-1',
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instanceId: 'my-instance',
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domainName: 'db.example.com',
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},
192+
'should use domain name'
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);
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195+
t.same(
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await resolveInstanceName('my-project:region-1:my-instance'),
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{
198+
projectId: 'my-project',
199+
regionId: 'region-1',
200+
instanceId: 'my-instance',
201+
domainName: undefined,
202+
},
203+
'should use instance name'
204+
);
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206+
t.rejects(
207+
async () => await resolveInstanceName('bad.example.com'),
208+
{code: 'EBADDOMAINCONNECTIONNAME'},
209+
'should throw type error if an extra item is provided'
210+
);
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212+
t.rejects(
213+
async () => await resolveInstanceName('no-record.example.com'),
214+
{code: 'EDOMAINNAMELOOKUPERROR'},
215+
'should throw type error if an extra item is provided'
216+
);
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218+
t.rejects(
219+
async () => await resolveInstanceName(''),
220+
{code: 'ENOCONNECTIONNAME'},
221+
'should throw type error if the connection name is empty'
222+
);
223+
t.rejects(
224+
async () => await resolveInstanceName('bad-name'),
225+
{code: 'EBADCONNECTIONNAME'},
226+
'should throw type error if the connection name is empty'
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);
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});

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