chore: address review comment + fix test

Author: olavloite

google-cloud-spanner/src/main/java/com/google/cloud/spanner/MultiplexedSessionDatabaseClient.java

@@ -53,6 +53,15 @@
  * transactions.
  */
 final class MultiplexedSessionDatabaseClient extends AbstractMultiplexedSessionDatabaseClient {
+  /**
+   * The maximum number of attempts that the client will try to execute CreateSession for the
+   * initial multiplexed session. This value is only used for the very first multiplexed session
+   * that is created, and it is only used if the application has not set a waitForMinSessions value.
+   * If waitForMinSessions has been set, then the client will retry until the duration in
+   * waitForMinSessions has been reached.
+   */
+  private static final int MAX_INITIAL_CREATE_SESSION_ATTEMPTS = 10;
+
   @VisibleForTesting
   static final Statement DETERMINE_DIALECT_STATEMENT =
       Statement.newBuilder(
@@ -229,7 +238,8 @@ public void close() {
 
     Duration waitDuration =
         sessionClient.getSpanner().getOptions().getSessionPoolOptions().getWaitForMinSessions();
-    int initialAttempts = waitDuration == null || waitDuration.isZero() ? 10 : 1;
+    int initialAttempts =
+        waitDuration == null || waitDuration.isZero() ? MAX_INITIAL_CREATE_SESSION_ATTEMPTS : 1;
     asyncCreateMultiplexedSession(initialSessionReferenceFuture, initialAttempts);
     maybeWaitForSessionCreation(
         sessionClient.getSpanner().getOptions().getSessionPoolOptions(),

google-cloud-spanner/src/test/java/com/google/cloud/spanner/MultiplexedSessionDatabaseClientMockServerTest.java

@@ -377,12 +377,21 @@ public void testRetryWithNoSessionCreationWaitTime() {
             });
     assertEquals(ErrorCode.DEADLINE_EXCEEDED, spannerException.getErrorCode());
 
+    // The CreateSession RPC will be retried, and as the exception is removed by the first call,
+    // the second attempt will succeed.
+    try (ResultSet resultSet = client.singleUse().executeQuery(STATEMENT)) {
+      //noinspection StatementWithEmptyBody
+      while (resultSet.next()) {
+        // ignore
+      }
+    }
+
     List<CreateSessionRequest> createSessionRequests =
         mockSpanner.getRequestsOfType(CreateSessionRequest.class);
-    assertEquals(1, createSessionRequests.size());
+    assertEquals(2, createSessionRequests.size());
 
     List<ExecuteSqlRequest> requests = mockSpanner.getRequestsOfType(ExecuteSqlRequest.class);
-    assertEquals(0, requests.size());
+    assertEquals(1, requests.size());
 
     testSpanner.close();
   }