Add flight-controlled thread pool expansion for silent requests, Fixes AB#3492151 (#2865)

Fixes:
[AB#3492151](https://identitydivision.visualstudio.com/fac9d424-53d2-45c0-91b5-ef6ba7a6bf26/_workitems/edit/3492151)

Problem:
The Broker's silent token request thread pool (sSilentExecutor) is fixed
at 5 threads. Under high load scenarios with multiple concurrent ATS
requests from various client apps (Teams, Outlook, OneAuth), this can
cause request queuing, increased latency, and potential timeouts.

Solution:
Introduce a flight-controlled mechanism to expand the thread pool from 5
to 8 threads, applying ONLY to the Broker module (not MSAL client apps).

Changes:
- CommonFlight.java: Add ENABLE_EXPANDED_BROKER_SILENT_THREAD_POOL
flight (default: false)
- CommandDispatcher.java: Add initializeSilentExecutorForBroker() and
resetSilentRequestExecutorWithSize() methods with graceful executor
shutdown handling
- AndroidBrokerFlightsManager.kt: Call initializeBrokerSilentExecutor()
during Broker initialization after flights are loaded

Key design decisions:
- Uses Android process isolation: Broker runs in separate process, so
static sSilentExecutor is independent from MSAL client apps
- Broker-only initialization: AndroidBrokerFlightsManager is
Broker-specific code that MSAL apps never call
- Flight-controlled: Safe rollout via ECS with instant rollback
capability
- Graceful shutdown: Existing executor is properly terminated before
creating expanded pool

---------

Co-authored-by: prsaminathan <[email protected]>

Author: Prvnkmr337

changelog.txt

@@ -5,6 +5,7 @@ vNext
 - [MINOR] Cleanup code related to emitting ests telemetry (#2868)
 - [MINOR] Skip account aggregation when responding to AcquireTokenSilent api call for OneAuth (#2863)
 - [MINOR] Introduce locks at NameValueStorageFileManagerSimpleCacheImpl layer (#2842)
+- [MINOR] Add flight-controlled option to expand Broker CommandDispatcher silent thread pool to 8 threads (default remains 5; MSAL clients unaffected) (#2865)
 - [PATCH] Implement State-Based Timeout Classification for Silent Token Requests (#2870)
 - [MINOR] Added Authentication Constants to be used for broker version and name (#2859)
 - [PATCH] Adding WebAppsNonce to JWT request body (#2867)

common/src/androidTest/java/com/microsoft/identity/common/CommandDispatcherTest.java

@@ -33,6 +33,7 @@
 
 import com.microsoft.identity.common.components.AndroidPlatformComponentsFactory;
 import com.microsoft.identity.common.internal.commands.RefreshOnCommand;
+import com.microsoft.identity.common.java.AuthenticationConstants;
 import com.microsoft.identity.common.java.cache.CacheRecord;
 import com.microsoft.identity.common.java.cache.ICacheRecord;
 import com.microsoft.identity.common.java.commands.BaseCommand;
@@ -54,6 +55,7 @@
 import com.microsoft.identity.common.java.dto.IdTokenRecord;
 import com.microsoft.identity.common.java.dto.RefreshTokenRecord;
 import com.microsoft.identity.common.java.exception.ClientException;
+import com.microsoft.identity.common.java.exception.ErrorStrings;
 import com.microsoft.identity.common.java.exception.ServiceException;
 import com.microsoft.identity.common.java.exception.TerminalException;
 import com.microsoft.identity.common.java.providers.oauth2.AuthorizationResult;
@@ -433,6 +435,114 @@ public void testResetSilentRequestExecutor() throws Exception {
         Assert.assertEquals(TEST_RESULT_STR, result.getResult());
     }
 
+    /**
+     * Tests that initializeSilentExecutorWithExpandedPool() correctly expands the thread pool
+     * when called with a valid Broker package name (Azure Authenticator).
+     */
+    @Test
+    public void testInitializeSilentExecutorWithExpandedPool_WithValidBrokerPackage() throws Exception {
+        CommandDispatcher.clearState();
+
+        // Test with Azure Authenticator package
+        CommandDispatcher.initializeSilentExecutorWithExpandedPool(
+                AuthenticationConstants.Broker.AZURE_AUTHENTICATOR_APP_PACKAGE_NAME);
+
+        // Verify executor is functional
+        verifyExecutorIsFunctional();
+
+        CommandDispatcher.clearState();
+    }
+
+    /**
+     * Tests that initializeSilentExecutorWithExpandedPool() works with all valid Broker packages.
+     */
+    @Test
+    public void testInitializeSilentExecutorWithExpandedPool_AllBrokerPackages() throws Exception {
+        final String[] brokerPackages = {
+                AuthenticationConstants.Broker.AZURE_AUTHENTICATOR_APP_PACKAGE_NAME,
+                AuthenticationConstants.Broker.LTW_APP_PACKAGE_NAME,
+                AuthenticationConstants.Broker.COMPANY_PORTAL_APP_PACKAGE_NAME
+        };
+
+        for (final String packageName : brokerPackages) {
+            CommandDispatcher.clearState();
+            CommandDispatcher.initializeSilentExecutorWithExpandedPool(packageName);
+            verifyExecutorIsFunctional();
+        }
+
+        CommandDispatcher.clearState();
+    }
+
+    /**
+     * Tests that initializeSilentExecutorWithExpandedPool() throws ClientException
+     * when called with a non-Broker package name.
+     */
+    @Test
+    public void testInitializeSilentExecutorWithExpandedPool_WithNonBrokerPackage_ThrowsException() throws Exception {
+        CommandDispatcher.clearState();
+
+        try {
+            CommandDispatcher.initializeSilentExecutorWithExpandedPool("com.some.msal.app");
+            Assert.fail("Expected ClientException to be thrown for non-Broker package");
+        } catch (final ClientException e) {
+            Assert.assertEquals(ErrorStrings.BROKER_ONLY_OPERATION, e.getErrorCode());
+            // Verify message does NOT contain the package name (no sensitive info leak)
+            Assert.assertFalse(e.getMessage().contains("com.some.msal.app"));
+        } finally {
+            CommandDispatcher.clearState();
+        }
+    }
+
+    /**
+     * Tests that initializeSilentExecutorWithExpandedPool() throws NullPointerException
+     * when called with null package name due to @NonNull annotation enforcement.
+     * Passing null is a programming error and should fail fast.
+     */
+    @Test(expected = NullPointerException.class)
+    public void testInitializeSilentExecutorWithExpandedPool_WithNullPackage_ThrowsException() throws Exception {
+        CommandDispatcher.clearState();
+        try {
+            CommandDispatcher.initializeSilentExecutorWithExpandedPool(null);
+        } finally {
+            CommandDispatcher.clearState();
+        }
+    }
+
+    /**
+     * Tests that initializeSilentExecutorWithExpandedPool() throws ClientException
+     * when called with empty package name.
+     */
+    @Test
+    public void testInitializeSilentExecutorWithExpandedPool_WithEmptyPackage_ThrowsException()  throws Exception {
+        CommandDispatcher.clearState();
+
+        try {
+            CommandDispatcher.initializeSilentExecutorWithExpandedPool("");
+            Assert.fail("Expected ClientException to be thrown for empty package");
+        } catch (final ClientException e) {
+            Assert.assertEquals(ErrorStrings.BROKER_ONLY_OPERATION, e.getErrorCode());
+        } finally {
+            CommandDispatcher.clearState();
+        }
+    }
+
+    /**
+     * Helper method to verify the silent executor is functional after initialization.
+     */
+    private void verifyExecutorIsFunctional() throws Exception {
+        final CountDownLatch testLatch = new CountDownLatch(1);
+        final TestCommand testCommand = getTestCommand(testLatch);
+
+        final FinalizableResultFuture<CommandResult> future = CommandDispatcher.submitSilentReturningFuture(testCommand);
+        testLatch.await();
+
+        final CommandResult result = future.get();
+        Assert.assertEquals(ICommandResult.ResultStatus.COMPLETED, result.getStatus());
+        Assert.assertEquals(TEST_RESULT_STR, result.getResult());
+        Assert.assertTrue(future.isDone());
+        future.isCleanedUp();
+    }
+
     private TestCommand getTestCommand(final CountDownLatch testLatch) {
         return new TestCommand(
                 getEmptyTestParams(),

common/src/main/java/com/microsoft/identity/common/internal/result/MsalBrokerResultAdapter.java

@@ -24,6 +24,7 @@
 
 import static com.microsoft.identity.common.java.AuthenticationConstants.Broker.BROKER_REQUEST_RECEIVED_TIMESTAMP;
 import static com.microsoft.identity.common.java.AuthenticationConstants.Broker.BROKER_RESPONSE_GENERATION_TIMESTAMP;
+import static com.microsoft.identity.common.java.AuthenticationConstants.Broker.BROKER_SILENT_EXECUTOR_POOL_SIZE;
 import static com.microsoft.identity.common.adal.internal.AuthenticationConstants.Broker.BROKER_ACCOUNTS;
 import static com.microsoft.identity.common.adal.internal.AuthenticationConstants.Broker.BROKER_ACCOUNTS_COMPRESSED;
 import static com.microsoft.identity.common.adal.internal.AuthenticationConstants.Broker.BROKER_ACTIVITY_NAME;
@@ -65,6 +66,7 @@
 import com.microsoft.identity.common.java.broker.BrokerPerformanceMetrics;
 import com.microsoft.identity.common.java.cache.CacheRecord;
 import com.microsoft.identity.common.java.cache.ICacheRecord;
+import com.microsoft.identity.common.java.controllers.CommandDispatcher;
 import com.microsoft.identity.common.java.commands.AcquirePrtSsoTokenBatchResult;
 import com.microsoft.identity.common.java.commands.AcquirePrtSsoTokenResult;
 import com.microsoft.identity.common.java.commands.webapps.WebAppsAccountItem;
@@ -537,11 +539,16 @@ public BrokerPerformanceMetrics getBrokerPerformanceMetricsFromBundle(@NonNull f
                 BROKER_RESPONSE_GENERATION_TIMESTAMP,
                 INVALID_TIMESTAMP
         );
+        final int silentExecutorPoolSize = resultBundle.getInt(
+                BROKER_SILENT_EXECUTOR_POOL_SIZE,
+                CommandDispatcher.getDefaultSilentExecutorPoolSize()
+        );
 
         if (brokerRequestReceivedTimestamp != INVALID_TIMESTAMP && brokerResponseGenerationTimestamp != INVALID_TIMESTAMP) {
             return new BrokerPerformanceMetrics(
                     brokerRequestReceivedTimestamp,
-                    brokerResponseGenerationTimestamp
+                    brokerResponseGenerationTimestamp,
+                    silentExecutorPoolSize
             );
         } else {
             Logger.warn(TAG, "Broker performance metrics not found in the result bundle.");

common4j/src/main/com/microsoft/identity/common/java/AuthenticationConstants.java

@@ -521,6 +521,21 @@ public static final class AAD {
     @NoArgsConstructor(access = AccessLevel.PRIVATE)
     public static final class Broker {
 
+        /**
+         * Azure Authenticator app package name.
+         */
+        public static final String AZURE_AUTHENTICATOR_APP_PACKAGE_NAME = "com.azure.authenticator";
+
+        /**
+         * Company Portal app package name.
+         */
+        public static final String COMPANY_PORTAL_APP_PACKAGE_NAME = "com.microsoft.windowsintune.companyportal";
+
+        /**
+         * Package name of the Link To Windows app.
+         */
+        public static final String LTW_APP_PACKAGE_NAME = "com.microsoft.appmanager";
+
         /**
          * Default timeout for broker tasks/futures.
          */
@@ -578,6 +593,12 @@ public static final class Broker {
          */
         public static final String BROKER_RESPONSE_GENERATION_TIMESTAMP = "broker_response_generation_timestamp";
 
+        /**
+         * Key for the silent executor pool size in broker response bundles.
+         * Used by clients (e.g., OneAuth) to recreate BrokerPerformanceMetrics.
+         */
+        public static final String BROKER_SILENT_EXECUTOR_POOL_SIZE = "broker_silent_executor_pool_size";
+
         /**
          * Broker application version name.
          */

common4j/src/main/com/microsoft/identity/common/java/broker/BrokerPerformanceMetrics.kt

@@ -22,6 +22,7 @@
 //  THE SOFTWARE.
 package com.microsoft.identity.common.java.broker
 
+import com.microsoft.identity.common.java.controllers.CommandDispatcher
 import com.microsoft.identity.common.java.logging.Logger
 
 /**
@@ -39,7 +40,14 @@ class BrokerPerformanceMetrics(
      * Timestamp when the broker generated the authentication response (epoch milliseconds).
      * Used to calculate both broker handling time and response latency.
      */
-    val brokerResponseGenerationTimestamp: Long
+    val brokerResponseGenerationTimestamp: Long,
+
+    /**
+     * The configured pool size of the silent executor at the time of the request.
+     * Helps diagnose concurrency-related performance issues.
+     * Defaults to the standard silent executor pool size.
+     */
+    val silentExecutorPoolSize: Int
 ) {
     /**
      * Time spent by broker processing the request (in milliseconds).
@@ -70,7 +78,8 @@ class BrokerPerformanceMetrics(
                 "brokerHandlingTime=$brokerHandlingTime, " +
                 "responseLatency=$responseLatency, " +
                 "brokerRequestReceivedTimestamp=$brokerRequestReceivedTimestamp, " +
-                "brokerResponseGenerationTimestamp=$brokerResponseGenerationTimestamp)"
+                "brokerResponseGenerationTimestamp=$brokerResponseGenerationTimestamp, " +
+                "silentExecutorPoolSize=$silentExecutorPoolSize)"
     }
 
     companion object {