feat: Use multiplex sessions for RW and Partition Ops (googleapis#3996)

* feat: Use multiplex sessions for RW and Partition Ops

* Fix emulator tests

Author: sakthivelmanii

.kokoro/presubmit/integration-regular-sessions-enabled.cfg

@@ -35,4 +35,14 @@ env_vars: {
 env_vars: {
     key: "GOOGLE_CLOUD_SPANNER_MULTIPLEXED_SESSIONS"
     value: "false"
-}
+}
+
+env_vars: {
+    key: "GOOGLE_CLOUD_SPANNER_MULTIPLEXED_SESSIONS_PARTITIONED_OPS"
+    value: "false"
+}
+
+env_vars: {
+    key: "GOOGLE_CLOUD_SPANNER_MULTIPLEXED_SESSIONS_FOR_RW"
+    value: "false"
+}

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

@@ -619,13 +619,13 @@ public static class Builder {
     // client.
     // Set useMultiplexedSessionForRW to true to make multiplexed session for RW operations the
     // default.
-    private boolean useMultiplexedSessionForRW = false;
+    private boolean useMultiplexedSessionForRW = true;
 
     // This field controls the default behavior of session management for Partitioned operations in
     // Java client.
     // Set useMultiplexedSessionPartitionedOps to true to make multiplexed session for Partitioned
     // operations the default.
-    private boolean useMultiplexedSessionPartitionedOps = false;
+    private boolean useMultiplexedSessionPartitionedOps = true;
 
     private Duration multiplexedSessionMaintenanceDuration = Duration.ofDays(7);
     private Clock poolMaintainerClock = Clock.INSTANCE;

google-cloud-spanner/src/test/java/com/google/cloud/spanner/it/ITDatabaseTest.java

@@ -150,7 +150,9 @@ public void databaseDeletedTest() throws Exception {
         }
       }
     }
-    assertThat(notFoundException).isNotNull();
+    if (!isUsingEmulator()) {
+      assertThat(notFoundException).isNotNull();
+    }
 
     // Now get a new DatabaseClient for the database. This should now result in a valid
     // DatabaseClient.

google-cloud-spanner/src/test/java/com/google/cloud/spanner/it/ITJsonWriteReadTest.java

@@ -16,6 +16,7 @@
 
 package com.google.cloud.spanner.it;
 
+import static com.google.cloud.spanner.testing.EmulatorSpannerHelper.isUsingEmulator;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertThrows;
 
@@ -132,10 +133,8 @@ public void testWriteAndReadInvalidJsonValues() throws IOException {
                               .to(Value.json(jsonStr))
                               .build())));
 
-      if (env.getTestHelper()
-          .getOptions()
-          .getSessionPoolOptions()
-          .getUseMultiplexedSessionForRW()) {
+      if (env.getTestHelper().getOptions().getSessionPoolOptions().getUseMultiplexedSessionForRW()
+          && !isUsingEmulator()) {
         assertEquals(ErrorCode.INVALID_ARGUMENT, exception.getErrorCode());
       } else {
         assertEquals(ErrorCode.FAILED_PRECONDITION, exception.getErrorCode());

google-cloud-spanner/src/test/java/com/google/cloud/spanner/it/ITWriteTest.java

@@ -1081,10 +1081,8 @@ public void incorrectType() {
       write(baseInsert().set("StringValue").to(1.234).build());
       fail("Expected exception");
     } catch (SpannerException ex) {
-      if (env.getTestHelper()
-          .getOptions()
-          .getSessionPoolOptions()
-          .getUseMultiplexedSessionForRW()) {
+      if (env.getTestHelper().getOptions().getSessionPoolOptions().getUseMultiplexedSessionForRW()
+          && !isUsingEmulator()) {
         assertThat(ex.getErrorCode()).isEqualTo(ErrorCode.INVALID_ARGUMENT);
       } else {
         assertThat(ex.getErrorCode()).isEqualTo(ErrorCode.FAILED_PRECONDITION);