chore: add flag to force-disable multiplexed sessions (googleapis#3083)

Adds an environment variable that can be used to force-disable the use of multiplexed sessions.

Author: olavloite

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

@@ -105,7 +105,11 @@ private SessionPoolOptions(Builder builder) {
  this.randomizePositionQPSThreshold = builder.randomizePositionQPSThreshold;
  this.inactiveTransactionRemovalOptions = builder.inactiveTransactionRemovalOptions;
  this.poolMaintainerClock = builder.poolMaintainerClock;
- this.useMultiplexedSession = builder.useMultiplexedSession;
+ // TODO: Remove when multiplexed sessions are guaranteed to be supported.
+ this.useMultiplexedSession =
+ builder.useMultiplexedSession
+ && !Boolean.parseBoolean(
+ System.getenv("GOOGLE_CLOUD_SPANNER_FORCE_DISABLE_MULTIPLEXED_SESSIONS"));
  this.useRandomChannelHint = builder.useRandomChannelHint;
  this.multiplexedSessionMaintenanceDuration = builder.multiplexedSessionMaintenanceDuration;
  }

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

@@ -17,16 +17,21 @@
 package com.google.cloud.spanner;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assume.assumeFalse;
+import static org.junit.Assume.assumeTrue;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
 import com.google.cloud.spanner.SessionClient.SessionConsumer;
+import java.lang.reflect.Field;
 import java.time.Clock;
 import java.time.Duration;
 import java.time.Instant;
-import org.junit.Ignore;
+import java.util.Map;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
@@ -35,9 +40,11 @@
 @RunWith(JUnit4.class)
 public class MultiplexedSessionDatabaseClientTest {
 
- @Ignore("Fails on native builds due to ues of reflection")
  @Test
  public void testMaintainer() {
+ // This fails for the native builds due to the extensive use of reflection.
+ assumeTrue(isJava8());
+
  Instant now = Instant.now();
  Clock clock = mock(Clock.class);
  when(clock.instant()).thenReturn(now);
@@ -101,4 +108,42 @@ public void testMaintainer() {
  client.getMaintainer().maintain();
  assertEquals(client.getCurrentSessionReference(), session2.getSessionReference());
  }
+
+ @Test
+ public void testForceDisableEnvVar() throws Exception {
+ assumeTrue(isJava8());
+ assumeFalse(
+ System.getenv().containsKey("GOOGLE_CLOUD_SPANNER_FORCE_DISABLE_MULTIPLEXED_SESSIONS"));
+
+ // Assert that the mux sessions setting is respected by default.
+ assertTrue(
+ SessionPoolOptions.newBuilder()
+ .setUseMultiplexedSession(true)
+ .build()
+ .getUseMultiplexedSession());
+
+ Class<?> classOfMap = System.getenv().getClass();
+ Field field = classOfMap.getDeclaredField("m");
+ field.setAccessible(true);
+ Map<String, String> writeableEnvironmentVariables =
+ (Map<String, String>) field.get(System.getenv());
+
+ try {
+ writeableEnvironmentVariables.put(
+ "GOOGLE_CLOUD_SPANNER_FORCE_DISABLE_MULTIPLEXED_SESSIONS", "true");
+ // Assert that the env var overrides the mux sessions setting.
+ assertFalse(
+ SessionPoolOptions.newBuilder()
+ .setUseMultiplexedSession(true)
+ .build()
+ .getUseMultiplexedSession());
+ } finally {
+ writeableEnvironmentVariables.remove(
+ "GOOGLE_CLOUD_SPANNER_FORCE_DISABLE_MULTIPLEXED_SESSIONS");
+ }
+ }
+
+ private boolean isJava8() {
+ return JavaVersionUtil.getJavaMajorVersion() == 8;
+ }
 }