chore(spanner): support multiplexed session for rw transactions in ex… (googleapis#3471)

* chore(spanner): support multiplexed session for rw transactions in executor

* chore(spanner): lint fix

Author: harshachinta

google-cloud-spanner-executor/src/main/java/com/google/cloud/executor/spanner/CloudClientExecutor.java

@@ -829,10 +829,15 @@ private synchronized Spanner getClient(long timeoutSeconds, boolean useMultiplex
 
     com.google.cloud.spanner.SessionPoolOptions.Builder poolOptionsBuilder =
         com.google.cloud.spanner.SessionPoolOptions.newBuilder();
-    SessionPoolOptionsHelper.setUseMultiplexedSession(
-        com.google.cloud.spanner.SessionPoolOptions.newBuilder(), useMultiplexedSession);
+    SessionPoolOptionsHelper.setUseMultiplexedSession(poolOptionsBuilder, useMultiplexedSession);
     SessionPoolOptionsHelper.setUseMultiplexedSessionBlindWrite(
-        com.google.cloud.spanner.SessionPoolOptions.newBuilder(), useMultiplexedSession);
+        poolOptionsBuilder, useMultiplexedSession);
+    SessionPoolOptionsHelper.setUseMultiplexedSessionForRW(
+        poolOptionsBuilder, useMultiplexedSession);
+    LOGGER.log(
+        Level.INFO,
+        String.format(
+            "Using multiplexed sessions for read-write transactions: %s", useMultiplexedSession));
     com.google.cloud.spanner.SessionPoolOptions sessionPoolOptions = poolOptionsBuilder.build();
     // Cloud Spanner Client does not support global retry settings,
     // Thus, we need to add retry settings to each individual stub.

google-cloud-spanner-executor/src/main/java/com/google/cloud/spanner/SessionPoolOptionsHelper.java

@@ -38,4 +38,10 @@ public static SessionPoolOptions.Builder setUseMultiplexedSessionBlindWrite(
     return sessionPoolOptionsBuilder.setUseMultiplexedSessionBlindWrite(
         useMultiplexedSessionBlindWrite);
   }
+
+  // TODO: Remove when multiplexed session for read write is released.
+  public static SessionPoolOptions.Builder setUseMultiplexedSessionForRW(
+      SessionPoolOptions.Builder sessionPoolOptionsBuilder, boolean useMultiplexedSessionForRW) {
+    return sessionPoolOptionsBuilder.setUseMultiplexedSessionForRW(useMultiplexedSessionForRW);
+  }
 }