Fix race in AzureClient factory fetch (#16525)

* Fix race in AzureClient factory fetch

* Fixing forbidden check.

* Renaming variable.

extensions-core/azure-extensions/src/main/java/org/apache/druid/storage/azure/AzureClientFactory.java

@@ -32,8 +32,8 @@ import org.apache.druid.java.util.common.Pair;
 
 import javax.annotation.Nullable;
 import java.time.Duration;
-import java.util.HashMap;
 import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 
 /**
  * Factory class for generating BlobServiceClient objects used for deep storage.
@@ -47,7 +47,7 @@ public class AzureClientFactory
   public AzureClientFactory(AzureAccountConfig config)
   {
     this.config = config;
-    this.cachedBlobServiceClients = new HashMap<>();
+    this.cachedBlobServiceClients = new ConcurrentHashMap<>();
   }
 
   // It's okay to store clients in a map here because all the configs for specifying azure retries are static, and there are only 2 of them.

extensions-core/azure-extensions/src/test/java/org/apache/druid/storage/azure/AzureClientFactoryTest.java

@@ -24,11 +24,16 @@ import com.azure.core.http.policy.BearerTokenAuthenticationPolicy;
 import com.azure.storage.blob.BlobServiceClient;
 import com.azure.storage.common.StorageSharedKeyCredential;
 import com.google.common.collect.ImmutableMap;
+import org.apache.druid.java.util.common.concurrent.Execs;
 import org.junit.Assert;
 import org.junit.Test;
 
 import java.net.MalformedURLException;
 import java.net.URL;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicReference;
 
 public class AzureClientFactoryTest
 {
@@ -173,4 +178,51 @@ public class AzureClientFactoryTest
     BlobServiceClient blobServiceClient = azureClientFactory.getBlobServiceClient(null, ACCOUNT);
     Assert.assertEquals(expectedAccountUrl.toString(), blobServiceClient.getAccountUrl());
   }
+
+  @Test
+  public void test_concurrent_azureClientFactory_gets() throws Exception
+  {
+    for (int i = 0; i < 10; i++) {
+      concurrentAzureClientFactoryGets();
+    }
+  }
+
+  private void concurrentAzureClientFactoryGets() throws Exception
+  {
+    final int threads = 100;
+    String endpointSuffix = "core.nonDefault.windows.net";
+    String storageAccountEndpointSuffix = "ABC123.blob.storage.azure.net";
+    AzureAccountConfig config = new AzureAccountConfig();
+    config.setKey("key");
+    config.setEndpointSuffix(endpointSuffix);
+    config.setStorageAccountEndpointSuffix(storageAccountEndpointSuffix);
+    final AzureClientFactory localAzureClientFactory = new AzureClientFactory(config);
+    final URL expectedAccountUrl = new URL(
+        AzureAccountConfig.DEFAULT_PROTOCOL,
+        ACCOUNT + "." + storageAccountEndpointSuffix,
+        ""
+    );
+
+    final CountDownLatch latch = new CountDownLatch(threads);
+    ExecutorService executorService = Execs.multiThreaded(threads, "azure-client-fetcher-%d");
+    final AtomicReference<Exception> failureException = new AtomicReference<>();
+    for (int i = 0; i < threads; i++) {
+      final int retry = i % 2;
+      executorService.submit(() -> {
+        try {
+          latch.countDown();
+          latch.await();
+          BlobServiceClient blobServiceClient = localAzureClientFactory.getBlobServiceClient(retry, ACCOUNT);
+          Assert.assertEquals(expectedAccountUrl.toString(), blobServiceClient.getAccountUrl());
+        }
+        catch (Exception e) {
+          failureException.compareAndSet(null, e);
+        }
+      });
+    }
+    executorService.awaitTermination(1000, TimeUnit.MICROSECONDS);
+    if (failureException.get() != null) {
+      throw failureException.get();
+    }
+  }
 }