fix(auth): debounce getToken() function (#6282)

## Problem:

The Identity team noticed a large spike in token refreshes for specific
users. One user would trigger refresh over 50 times within a few
seconds.

Ticket: `P180886632`

## Solution:

The telemetry showed that `getChatAuthState()` was being called many
times in a short period. This eventually triggered the token refresh
logic many times, if the token was expired.

The solution is to add a debounce to `getToken()` which calls the
refresh logic.
- `debounce()` only accepts functions without any args, the refresh
logic requires args
- `getToken()` will also load from disk is the token is not expired, so
debouncing here saves disk I/O as well.

The current debounce interval is 100 milliseconds, which based on
telemetry should be enough to capture the barrage of calls. With some
manual testing it does not feel like UX is impacted in any noticeable
way.

---

- Treat all work as PUBLIC. Private `feature/x` branches will not be
squash-merged at release time.
- Your code changes must meet the guidelines in
[CONTRIBUTING.md](https://github.com/aws/aws-toolkit-vscode/blob/master/CONTRIBUTING.md#guidelines).
- License: I confirm that my contribution is made under the terms of the
Apache 2.0 license.

---------

Signed-off-by: nkomonen-amazon <nkomonen@amazon.com>

packages/core/src/auth/sso/ssoAccessTokenProvider.ts

@@ -33,7 +33,7 @@ import { randomUUID } from '../../shared/crypto'
 import { getExtRuntimeContext } from '../../shared/vscode/env'
 import { showInputBox } from '../../shared/ui/inputPrompter'
 import { AmazonQPromptSettings, DevSettings, PromptSettings, ToolkitPromptSettings } from '../../shared/settings'
-import { onceChanged } from '../../shared/utilities/functionUtils'
+import { debounce, onceChanged } from '../../shared/utilities/functionUtils'
 import { NestedMap } from '../../shared/utilities/map'
 import { asStringifiedStack } from '../../shared/telemetry/spans'
 import { showViewLogsMessage } from '../../shared/utilities/messages'
@@ -97,7 +97,20 @@ export abstract class SsoAccessTokenProvider {
         this.reAuthState.set(this.profile, { reAuthReason: `invalidate():${reason}` })
     }
 
+    /**
+     * Sometimes we get many calls at once and this
+     * can trigger redundant disk reads, or token refreshes.
+     * We debounce to avoid this.
+     *
+     * NOTE: The property {@link getTokenDebounced()} does not work with being stubbed for tests, so
+     * this redundant function was created to work around that.
+     */
     public async getToken(): Promise<SsoToken | undefined> {
+        return this.getTokenDebounced()
+    }
+    private getTokenDebounced = debounce(() => this._getToken(), 50)
+    /** Exposed for testing purposes only */
+    public async _getToken(): Promise<SsoToken | undefined> {
         const data = await this.cache.token.load(this.tokenCacheKey)
         SsoAccessTokenProvider.logIfChanged(
             indent(

packages/core/src/test/credentials/provider/sharedCredentialsProvider.test.ts

@@ -4,13 +4,11 @@
  */
 
 import assert from 'assert'
-import * as FakeTimers from '@sinonjs/fake-timers'
 import * as sinon from 'sinon'
 import { SharedCredentialsProvider } from '../../../auth/providers/sharedCredentialsProvider'
 import { stripUndefined } from '../../../shared/utilities/collectionUtils'
 import * as process from '@aws-sdk/credential-provider-process'
 import { ParsedIniData } from '@smithy/shared-ini-file-loader'
-import { installFakeClock } from '../../testUtil'
 import { SsoClient } from '../../../auth/sso/clients'
 import { stub } from '../../utilities/stubber'
 import { SsoAccessTokenProvider } from '../../../auth/sso/ssoAccessTokenProvider'
@@ -19,20 +17,13 @@ import { createTestSections } from '../testUtil'
 const missingPropertiesFragment = 'missing properties'
 
 describe('SharedCredentialsProvider', async function () {
-    let clock: FakeTimers.InstalledClock
     let sandbox: sinon.SinonSandbox
 
     before(function () {
         sandbox = sinon.createSandbox()
-        clock = installFakeClock()
-    })
-
-    after(function () {
-        clock.uninstall()
     })
 
     afterEach(function () {
-        clock.reset()
         sandbox.restore()
     })
 

packages/core/src/test/credentials/sso/ssoAccessTokenProvider.test.ts

@@ -27,6 +27,7 @@ import { ToolkitError } from '../../../shared/errors'
 import * as fs from 'fs' // eslint-disable-line no-restricted-imports
 import * as path from 'path'
 import { Stub, stub } from '../../utilities/stubber'
+import { globals } from '../../../shared'
 
 const hourInMs = 3600000
 
@@ -37,14 +38,14 @@ describe('SsoAccessTokenProvider', function () {
     let oidcClient: Stub<OidcClient>
     let sut: SsoAccessTokenProvider
     let cache: ReturnType<typeof getCache>
-    let clock: FakeTimers.InstalledClock
+    let clock: FakeTimers.InstalledClock | undefined
     let tempDir: string
     let reAuthState: TestReAuthState
 
     function createToken(timeDelta: number, extras: Partial<SsoToken> = {}) {
         return {
             accessToken: 'dummyAccessToken',
-            expiresAt: new clock.Date(clock.Date.now() + timeDelta),
+            expiresAt: new globals.clock.Date(globals.clock.Date.now() + timeDelta),
             ...extras,
         }
     }
@@ -54,7 +55,7 @@ describe('SsoAccessTokenProvider', function () {
             scopes: [],
             clientId: 'dummyClientId',
             clientSecret: 'dummyClientSecret',
-            expiresAt: new clock.Date(clock.Date.now() + timeDelta),
+            expiresAt: new globals.clock.Date(globals.clock.Date.now() + timeDelta),
             startUrl,
             ...extras,
         }
@@ -66,7 +67,7 @@ describe('SsoAccessTokenProvider', function () {
             deviceCode: 'dummyCode',
             userCode: 'dummyUserCode',
             verificationUri: 'dummyLink',
-            expiresAt: new clock.Date(clock.Date.now() + timeDelta),
+            expiresAt: new globals.clock.Date(globals.clock.Date.now() + timeDelta),
         }
     }
 
@@ -77,14 +78,6 @@ describe('SsoAccessTokenProvider', function () {
         return cacheDir
     }
 
-    before(function () {
-        clock = installFakeClock()
-    })
-
-    after(function () {
-        clock.uninstall()
-    })
-
     beforeEach(async function () {
         oidcClient = stub(OidcClient)
         tempDir = await makeTemporaryTokenCacheFolder()
@@ -95,7 +88,7 @@ describe('SsoAccessTokenProvider', function () {
 
     afterEach(async function () {
         sinon.restore()
-        clock.reset()
+        clock?.uninstall()
         await tryRemoveFolder(tempDir)
     })
 
@@ -163,6 +156,20 @@ describe('SsoAccessTokenProvider', function () {
             assert.strictEqual(cachedToken, undefined)
         })
 
+        it('concurrent calls are debounced', async function () {
+            const validToken = createToken(hourInMs)
+            await cache.token.save(startUrl, { region, startUrl, token: validToken })
+            const actualGetToken = sinon.spy(sut, '_getToken')
+
+            const result = await Promise.all([sut.getToken(), sut.getToken(), sut.getToken()])
+
+            // Subsequent other calls were debounced so this was only called once
+            assert.strictEqual(actualGetToken.callCount, 1)
+            for (const r of result) {
+                assert.deepStrictEqual(r, validToken)
+            }
+        })
+
         describe('Exceptions', function () {
             it('drops expired tokens if failure was a client-fault', async function () {
                 const exception = new UnauthorizedClientException({ message: '', $metadata: {} })
@@ -267,6 +274,7 @@ describe('SsoAccessTokenProvider', function () {
         })
 
         it(`emits session duration between logins of the same startUrl`, async function () {
+            clock = installFakeClock()
             setupFlow()
             stubOpen()
 
@@ -311,6 +319,7 @@ describe('SsoAccessTokenProvider', function () {
         })
 
         it('respects the device authorization expiration time', async function () {
+            clock = installFakeClock()
             setupFlow()
             stubOpen()
             const exception = new AuthorizationPendingException({ message: '', $metadata: {} })
@@ -352,7 +361,7 @@ describe('SsoAccessTokenProvider', function () {
             const registration = {
                 clientId: 'myExpiredClientId',
                 clientSecret: 'myExpiredClientSecret',
-                expiresAt: new clock.Date(clock.Date.now() - 1), // expired date
+                expiresAt: new globals.clock.Date(globals.clock.Date.now() - 1), // expired date
                 startUrl: key.startUrl,
             }
             await cache.registration.save(key, registration)