fix: allows setting custom user agent in any case (#1129)

Allows setting a custom user agent in any case, instead of only in lower
case.

Author: thiagotnunes

google-cloud-spanner/src/main/java/com/google/cloud/spanner/spi/v1/GapicSpannerRpc.java

@@ -77,7 +77,6 @@
 import com.google.common.base.MoreObjects;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
-import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.util.concurrent.RateLimiter;
 import com.google.common.util.concurrent.ThreadFactoryBuilder;
@@ -161,6 +160,7 @@
 import java.net.URLDecoder;
 import java.nio.charset.StandardCharsets;
 import java.util.Comparator;
+import java.util.HashMap;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
@@ -244,6 +244,8 @@ private void awaitTermination() throws InterruptedException {
   private static final int GRPC_KEEPALIVE_SECONDS = 2 * 60;
   private static final String USER_AGENT_KEY = "user-agent";
   private static final String CLIENT_LIBRARY_LANGUAGE = "spanner-java";
+  public static final String DEFAULT_USER_AGENT =
+      CLIENT_LIBRARY_LANGUAGE + "/" + GaxProperties.getLibraryVersion(GapicSpannerRpc.class);
 
   private final ManagedInstantiatingExecutorProvider executorProvider;
   private boolean rpcIsClosed;
@@ -305,18 +307,11 @@ public GapicSpannerRpc(final SpannerOptions options) {
                 GaxGrpcProperties.getGrpcTokenName(), GaxGrpcProperties.getGrpcVersion())
             .build();
 
-    HeaderProvider mergedHeaderProvider = options.getMergedHeaderProvider(internalHeaderProvider);
-    Map<String, String> headersWithUserAgent =
-        ImmutableMap.<String, String>builder()
-            .put(
-                USER_AGENT_KEY,
-                CLIENT_LIBRARY_LANGUAGE
-                    + "/"
-                    + GaxProperties.getLibraryVersion(GapicSpannerRpc.class))
-            .putAll(mergedHeaderProvider.getHeaders())
-            .build();
+    final HeaderProvider mergedHeaderProvider =
+        options.getMergedHeaderProvider(internalHeaderProvider);
+
     final HeaderProvider headerProviderWithUserAgent =
-        FixedHeaderProvider.create(headersWithUserAgent);
+        headerProviderWithUserAgentFrom(mergedHeaderProvider);
     this.metadataProvider =
         SpannerMetadataProvider.create(
             headerProviderWithUserAgent.getHeaders(),
@@ -494,6 +489,24 @@ public <RequestT, ResponseT> UnaryCallable<RequestT, ResponseT> createUnaryCalla
     }
   }
 
+  private static HeaderProvider headerProviderWithUserAgentFrom(HeaderProvider headerProvider) {
+    final Map<String, String> headersWithUserAgent = new HashMap<>(headerProvider.getHeaders());
+    String userAgent = null;
+    for (Map.Entry<String, String> entry : headersWithUserAgent.entrySet()) {
+      if (entry.getKey().equalsIgnoreCase(USER_AGENT_KEY)) {
+        userAgent = entry.getValue();
+        headersWithUserAgent.remove(entry.getKey());
+        break;
+      }
+    }
+
+    headersWithUserAgent.put(
+        USER_AGENT_KEY,
+        userAgent == null ? DEFAULT_USER_AGENT : userAgent + " " + DEFAULT_USER_AGENT);
+
+    return FixedHeaderProvider.create(headersWithUserAgent);
+  }
+
   private static void checkEmulatorConnection(
       SpannerOptions options,
       TransportChannelProvider channelProvider,

google-cloud-spanner/src/test/java/com/google/cloud/spanner/spi/v1/GapicSpannerRpcTest.java

@@ -24,7 +24,9 @@
 import static org.junit.Assume.assumeTrue;
 
 import com.google.api.core.ApiFunction;
+import com.google.api.gax.core.GaxProperties;
 import com.google.api.gax.rpc.ApiCallContext;
+import com.google.api.gax.rpc.HeaderProvider;
 import com.google.auth.oauth2.AccessToken;
 import com.google.auth.oauth2.OAuth2Credentials;
 import com.google.cloud.spanner.DatabaseAdminClient;
@@ -151,6 +153,8 @@ public class GapicSpannerRpcTest {
   private Server server;
   private InetSocketAddress address;
   private final Map<SpannerRpc.Option, Object> optionsMap = new HashMap<>();
+  private Metadata seenHeaders;
+  private String defaultUserAgent;
 
   @BeforeClass
   public static void checkNotEmulator() {
@@ -161,6 +165,7 @@ public static void checkNotEmulator() {
 
   @Before
   public void startServer() throws IOException {
+    defaultUserAgent = "spanner-java/" + GaxProperties.getLibraryVersion(GapicSpannerRpc.class);
     mockSpanner = new MockSpannerServiceImpl();
     mockSpanner.setAbortProbability(0.0D); // We don't want any unpredictable aborted transactions.
     mockSpanner.putStatementResult(StatementResult.query(SELECT1AND2, SELECT1_RESULTSET));
@@ -183,6 +188,7 @@ public <ReqT, RespT> ServerCall.Listener<ReqT> interceptCall(
                       ServerCall<ReqT, RespT> call,
                       Metadata headers,
                       ServerCallHandler<ReqT, RespT> next) {
+                    seenHeaders = headers;
                     String auth =
                         headers.get(Key.of("authorization", Metadata.ASCII_STRING_MARSHALLER));
                     assertThat(auth).isEqualTo("Bearer " + VARIABLE_OAUTH_TOKEN);
@@ -502,6 +508,50 @@ public void testAdminRequestsLimitExceededRetryAlgorithm() {
     assertThat(alg.shouldRetry(new Exception("random exception"), null)).isFalse();
   }
 
+  @Test
+  public void testDefaultUserAgent() {
+    final SpannerOptions options = createSpannerOptions();
+    try (final Spanner spanner = options.getService()) {
+      final DatabaseClient databaseClient =
+          spanner.getDatabaseClient(DatabaseId.of("[PROJECT]", "[INSTANCE]", "[DATABASE]"));
+
+      try (final ResultSet rs = databaseClient.singleUse().executeQuery(SELECT1AND2)) {
+        rs.next();
+      }
+
+      assertThat(seenHeaders.get(Key.of("user-agent", Metadata.ASCII_STRING_MARSHALLER)))
+          .contains(defaultUserAgent);
+    }
+  }
+
+  @Test
+  public void testCustomUserAgent() {
+    for (final String headerId : new String[] {"user-agent", "User-Agent", "USER-AGENT"}) {
+      final HeaderProvider userAgentHeaderProvider =
+          new HeaderProvider() {
+            @Override
+            public Map<String, String> getHeaders() {
+              final Map<String, String> headers = new HashMap<>();
+              headers.put(headerId, "test-agent");
+              return headers;
+            }
+          };
+      final SpannerOptions options =
+          createSpannerOptions().toBuilder().setHeaderProvider(userAgentHeaderProvider).build();
+      try (Spanner spanner = options.getService()) {
+        final DatabaseClient databaseClient =
+            spanner.getDatabaseClient(DatabaseId.of("[PROJECT]", "[INSTANCE]", "[DATABASE]"));
+
+        try (final ResultSet rs = databaseClient.singleUse().executeQuery(SELECT1AND2)) {
+          rs.next();
+        }
+
+        assertThat(seenHeaders.get(Key.of("user-agent", Metadata.ASCII_STRING_MARSHALLER)))
+            .contains("test-agent " + defaultUserAgent);
+      }
+    }
+  }
+
   @SuppressWarnings("rawtypes")
   private SpannerOptions createSpannerOptions() {
     String endpoint = address.getHostString() + ":" + server.getPort();