Deduplicate UserAgent other-info entries

databricks-sdk-java/src/main/java/com/databricks/sdk/core/UserAgent.java

@@ -6,6 +6,9 @@
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
+import java.util.Objects;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 
@@ -14,8 +17,8 @@ public class UserAgent {
   private static String productVersion = "0.0.0";
 
   private static class Info {
-    private String key;
-    private String value;
+    private final String key;
+    private final String value;
 
     public Info(String key, String value) {
       this.key = key;
@@ -29,9 +32,29 @@ public String getKey() {
     public String getValue() {
       return value;
     }
+
+    @Override
+    public boolean equals(Object o) {
+      if (this == o) {
+        return true;
+      }
+      if (!(o instanceof Info)) {
+        return false;
+      }
+      Info info = (Info) o;
+      return key.equals(info.key) && value.equals(info.value);
+    }
+
+    @Override
+    public int hashCode() {
+      return Objects.hash(key, value);
+    }
   }
 
-  private static final ArrayList<Info> otherInfo = new ArrayList<>();
+  // Callers such as JDBC drivers re-register the same entries on every connection, and asString()
+  // runs on every request, so entries are deduplicated and read without locking.
+  // Package-private for testing.
+  static final Set<Info> otherInfo = ConcurrentHashMap.newKeySet();
 
   // TODO: check if reading from
   // /META-INF/maven/com.databricks/databrics-sdk-java/pom.properties
@@ -96,9 +119,7 @@ public static void withPartner(String partner) {
   public static void withOtherInfo(String key, String value) {
     matchAlphanum(key);
     matchAlphanumOrSemVer(value);
-    synchronized (otherInfo) {
-      otherInfo.add(new Info(key, value));
-    }
+    otherInfo.add(new Info(key, value));
   }
 
   private static String osName() {
@@ -137,13 +158,10 @@ public static String asString() {
     if (!metaHarness.isEmpty()) {
       segments.add(String.format("meta-harness/%s", metaHarness));
     }
-    // Concurrent iteration over ArrayList must be guarded with synchronized.
-    synchronized (otherInfo) {
-      segments.addAll(
-          otherInfo.stream()
-              .map(e -> String.format("%s/%s", e.getKey(), e.getValue()))
-              .collect(Collectors.toSet()));
-    }
+    segments.addAll(
+        otherInfo.stream()
+            .map(e -> String.format("%s/%s", e.getKey(), e.getValue()))
+            .collect(Collectors.toSet()));
     return segments.stream().collect(Collectors.joining(" "));
   }
 

databricks-sdk-java/src/test/java/com/databricks/sdk/core/UserAgentLoadTest.java

@@ -21,12 +21,13 @@ public void testAsStringConcurrent() throws InterruptedException, ExecutionExcep
     List<Future<Boolean>> futures = new ArrayList<>();
     int successCount = 0;
     int failureCount = 0;
+    int otherInfoSizeBefore = UserAgent.otherInfo.size();
 
     // Add some user agent info
     Callable<Boolean> task =
         () -> {
           try {
-            UserAgent.withOtherInfo("key1", "value1");
+            UserAgent.withOtherInfo("load-test", "1.0.0");
             UserAgent.asString();
             return true;
           } catch (Exception e) {
@@ -60,5 +61,7 @@ public void testAsStringConcurrent() throws InterruptedException, ExecutionExcep
 
     // Optionally, you can assert that there were no failures
     assertEquals(0, failureCount);
+    // Concurrent registrations of the same entry add it once.
+    assertEquals(otherInfoSizeBefore + 1, UserAgent.otherInfo.size());
   }
 }

databricks-sdk-java/src/test/java/com/databricks/sdk/core/UserAgentTest.java

@@ -57,6 +57,23 @@ public void testUserAgentWithOtherInfo() {
     Assertions.assertTrue(userAgent.contains("key2/value2"));
   }
 
+  @Test
+  public void testUserAgentWithOtherInfoDeduplicated() {
+    int sizeBefore = UserAgent.otherInfo.size();
+    for (int i = 0; i < 1000; i++) {
+      UserAgent.withOtherInfo("dedup", "1.0.0");
+    }
+    Assertions.assertEquals(sizeBefore + 1, UserAgent.otherInfo.size());
+
+    // Same key with a different value is a separate entry.
+    UserAgent.withOtherInfo("dedup", "2.0.0");
+    Assertions.assertEquals(sizeBefore + 2, UserAgent.otherInfo.size());
+
+    String userAgent = UserAgent.asString();
+    Assertions.assertTrue(userAgent.contains("dedup/1.0.0"));
+    Assertions.assertTrue(userAgent.contains("dedup/2.0.0"));
+  }
+
   @Test
   public void testUserAgentWithInvalidKey() {
     Assertions.assertThrows(