chore: enable multplexed sessions for experimental host (#3676)

* chore: enable multplexed sessions for experimental host

* pr link added to experimentalApi annotations

* max sessions set to 0 for exp host

* comments addressed

* unit test added

* removed comment

* changed assert statement

Author: sagnghos

google-cloud-spanner/clirr-ignored-differences.xml

@@ -822,11 +822,11 @@
     <method>java.lang.Object runTransaction(com.google.cloud.spanner.connection.Connection$TransactionCallable)</method>
   </difference>
 
-  <!-- Added external host option -->
+  <!-- Added experimental host option -->
   <difference>
     <differenceType>7012</differenceType>
     <className>com/google/cloud/spanner/SpannerOptions$SpannerEnvironment</className>
-    <method>com.google.auth.oauth2.GoogleCredentials getDefaultExternalHostCredentials()</method>
+    <method>com.google.auth.oauth2.GoogleCredentials getDefaultExperimentalHostCredentials()</method>
   </difference>
 
   <!-- Default sequence kind -->

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

@@ -34,6 +34,7 @@ public class SessionPoolOptions {
   private static final int DEFAULT_MAX_SESSIONS = 400;
   private static final int DEFAULT_MIN_SESSIONS = 100;
   private static final int DEFAULT_INC_STEP = 25;
+  private static final int EXPERIMENTAL_HOST_REGULAR_SESSIONS = 0;
   private static final ActionOnExhaustion DEFAULT_ACTION = ActionOnExhaustion.BLOCK;
   private final int minSessions;
   private final int maxSessions;
@@ -89,8 +90,12 @@ private SessionPoolOptions(Builder builder) {
     // minSessions > maxSessions is only possible if the user has only set a value for maxSessions.
     // We allow that to prevent code that only sets a value for maxSessions to break if the
     // maxSessions value is less than the default for minSessions.
-    this.minSessions = Math.min(builder.minSessions, builder.maxSessions);
-    this.maxSessions = builder.maxSessions;
+    this.minSessions =
+        builder.isExperimentalHost
+            ? EXPERIMENTAL_HOST_REGULAR_SESSIONS
+            : Math.min(builder.minSessions, builder.maxSessions);
+    this.maxSessions =
+        builder.isExperimentalHost ? EXPERIMENTAL_HOST_REGULAR_SESSIONS : builder.maxSessions;
     this.incStep = builder.incStep;
     this.maxIdleSessions = builder.maxIdleSessions;
     this.writeSessionsFraction = builder.writeSessionsFraction;
@@ -114,26 +119,30 @@ private SessionPoolOptions(Builder builder) {
     // useMultiplexedSession priority => Environment var > private setter > client default
     Boolean useMultiplexedSessionFromEnvVariable = getUseMultiplexedSessionFromEnvVariable();
     this.useMultiplexedSession =
-        (useMultiplexedSessionFromEnvVariable != null)
-            ? useMultiplexedSessionFromEnvVariable
-            : builder.useMultiplexedSession;
+        builder.isExperimentalHost
+            || ((useMultiplexedSessionFromEnvVariable != null)
+                ? useMultiplexedSessionFromEnvVariable
+                : builder.useMultiplexedSession);
     // useMultiplexedSessionForRW priority => Environment var > private setter > client default
     Boolean useMultiplexedSessionForRWFromEnvVariable =
         getUseMultiplexedSessionForRWFromEnvVariable();
     this.useMultiplexedSessionForRW =
-        (useMultiplexedSessionForRWFromEnvVariable != null)
-            ? useMultiplexedSessionForRWFromEnvVariable
-            : builder.useMultiplexedSessionForRW;
+        builder.isExperimentalHost
+            || ((useMultiplexedSessionForRWFromEnvVariable != null)
+                ? useMultiplexedSessionForRWFromEnvVariable
+                : builder.useMultiplexedSessionForRW);
     // useMultiplexedSessionPartitionedOps priority => Environment var > private setter > client
     // default
     Boolean useMultiplexedSessionFromEnvVariablePartitionedOps =
         getUseMultiplexedSessionFromEnvVariablePartitionedOps();
     this.useMultiplexedSessionForPartitionedOps =
-        (useMultiplexedSessionFromEnvVariablePartitionedOps != null)
-            ? useMultiplexedSessionFromEnvVariablePartitionedOps
-            : builder.useMultiplexedSessionPartitionedOps;
+        builder.isExperimentalHost
+            || ((useMultiplexedSessionFromEnvVariablePartitionedOps != null)
+                ? useMultiplexedSessionFromEnvVariablePartitionedOps
+                : builder.useMultiplexedSessionPartitionedOps);
     this.multiplexedSessionMaintenanceDuration = builder.multiplexedSessionMaintenanceDuration;
-    this.skipVerifyingBeginTransactionForMuxRW = builder.skipVerifyingBeginTransactionForMuxRW;
+    this.skipVerifyingBeginTransactionForMuxRW =
+        builder.isExperimentalHost || builder.skipVerifyingBeginTransactionForMuxRW;
   }
 
   @Override
@@ -617,6 +626,7 @@ public static class Builder {
     private Duration multiplexedSessionMaintenanceDuration = Duration.ofDays(7);
     private Clock poolMaintainerClock = Clock.INSTANCE;
     private boolean skipVerifyingBeginTransactionForMuxRW = false;
+    private boolean isExperimentalHost = false;
 
     private static Position getReleaseToPositionFromSystemProperty() {
       // NOTE: This System property is a beta feature. Support for it can be removed in the future.
@@ -813,6 +823,12 @@ public Builder setWarnAndCloseIfInactiveTransactions() {
       return this;
     }
 
+    @InternalApi
+    public Builder setExperimentalHost() {
+      this.isExperimentalHost = true;
+      return this;
+    }
+
     /**
      * If there are inactive transactions, release the resources consumed by such transactions. A
      * transaction is classified as inactive if it executes for more than a system defined duration.

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

@@ -98,7 +98,6 @@
 import java.util.concurrent.ThreadFactory;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
-import java.util.regex.Pattern;
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.GuardedBy;
@@ -117,10 +116,7 @@ public class SpannerOptions extends ServiceOptions<Spanner, SpannerOptions> {
 
   private static final String API_SHORT_NAME = "Spanner";
   private static final String DEFAULT_HOST = "https://spanner.googleapis.com";
-  private static final String CLOUD_SPANNER_HOST_FORMAT = ".*\\.googleapis\\.com.*";
-
-  @VisibleForTesting
-  static final Pattern CLOUD_SPANNER_HOST_PATTERN = Pattern.compile(CLOUD_SPANNER_HOST_FORMAT);
+  private static final String EXPERIMENTAL_HOST_PROJECT_ID = "default";
 
   private static final ImmutableSet<String> SCOPES =
       ImmutableSet.of(
@@ -856,13 +852,13 @@ default String getMonitoringHost() {
       return null;
     }
 
-    default GoogleCredentials getDefaultExternalHostCredentials() {
+    default GoogleCredentials getDefaultExperimentalHostCredentials() {
       return null;
     }
   }
 
-  static final String DEFAULT_SPANNER_EXTERNAL_HOST_CREDENTIALS =
-      "SPANNER_EXTERNAL_HOST_AUTH_TOKEN";
+  static final String DEFAULT_SPANNER_EXPERIMENTAL_HOST_CREDENTIALS =
+      "SPANNER_EXPERIMENTAL_HOST_AUTH_TOKEN";
 
   /**
    * Default implementation of {@link SpannerEnvironment}. Reads all configuration from environment
@@ -921,8 +917,8 @@ public String getMonitoringHost() {
     }
 
     @Override
-    public GoogleCredentials getDefaultExternalHostCredentials() {
-      return getOAuthTokenFromFile(System.getenv(DEFAULT_SPANNER_EXTERNAL_HOST_CREDENTIALS));
+    public GoogleCredentials getDefaultExperimentalHostCredentials() {
+      return getOAuthTokenFromFile(System.getenv(DEFAULT_SPANNER_EXPERIMENTAL_HOST_CREDENTIALS));
     }
   }
 
@@ -991,7 +987,7 @@ public static class Builder
     private boolean enableBuiltInMetrics = SpannerOptions.environment.isEnableBuiltInMetrics();
     private String monitoringHost = SpannerOptions.environment.getMonitoringHost();
     private SslContext mTLSContext = null;
-    private boolean isExternalHost = false;
+    private boolean isExperimentalHost = false;
 
     private static String createCustomClientLibToken(String token) {
       return token + " " + ServiceOptions.getGoogApiClientLibName();
@@ -1484,14 +1480,20 @@ public Builder setDecodeMode(DecodeMode decodeMode) {
     @Override
     public Builder setHost(String host) {
       super.setHost(host);
-      if (!CLOUD_SPANNER_HOST_PATTERN.matcher(host).matches()) {
-        this.isExternalHost = true;
-      }
       // Setting a host should override any SPANNER_EMULATOR_HOST setting.
       setEmulatorHost(null);
       return this;
     }
 
+    @ExperimentalApi("https://github.com/googleapis/java-spanner/pull/3676")
+    public Builder setExperimentalHost(String host) {
+      super.setHost(host);
+      super.setProjectId(EXPERIMENTAL_HOST_PROJECT_ID);
+      setSessionPoolOption(SessionPoolOptions.newBuilder().setExperimentalHost().build());
+      this.isExperimentalHost = true;
+      return this;
+    }
+
     /**
      * Enables gRPC-GCP extension with the default settings. Do not set
      * GOOGLE_CLOUD_SPANNER_MULTIPLEXED_SESSIONS to true in combination with this option, as
@@ -1530,7 +1532,7 @@ public Builder setEmulatorHost(String emulatorHost) {
 
     /**
      * Configures mTLS authentication using the provided client certificate and key files. mTLS is
-     * only supported for external spanner hosts.
+     * only supported for experimental spanner hosts.
      *
      * @param clientCertificate Path to the client certificate file.
      * @param clientCertificateKey Path to the client private key file.
@@ -1657,8 +1659,8 @@ public SpannerOptions build() {
         this.setChannelConfigurator(ManagedChannelBuilder::usePlaintext);
         // As we are using plain text, we should never send any credentials.
         this.setCredentials(NoCredentials.getInstance());
-      } else if (isExternalHost && credentials == null) {
-        credentials = environment.getDefaultExternalHostCredentials();
+      } else if (isExperimentalHost && credentials == null) {
+        credentials = environment.getDefaultExperimentalHostCredentials();
       }
       if (this.numChannels == null) {
         this.numChannels =
@@ -1700,8 +1702,8 @@ public static void useDefaultEnvironment() {
   }
 
   @InternalApi
-  public static GoogleCredentials getDefaultExternalHostCredentialsFromSysEnv() {
-    return getOAuthTokenFromFile(System.getenv(DEFAULT_SPANNER_EXTERNAL_HOST_CREDENTIALS));
+  public static GoogleCredentials getDefaultExperimentalCredentialsFromSysEnv() {
+    return getOAuthTokenFromFile(System.getenv(DEFAULT_SPANNER_EXPERIMENTAL_HOST_CREDENTIALS));
   }
 
   private static @Nullable GoogleCredentials getOAuthTokenFromFile(@Nullable String file) {

google-cloud-spanner/src/main/java/com/google/cloud/spanner/connection/ConnectionOptions.java

@@ -32,6 +32,7 @@
 import static com.google.cloud.spanner.connection.ConnectionProperties.ENABLE_EXTENDED_TRACING;
 import static com.google.cloud.spanner.connection.ConnectionProperties.ENCODED_CREDENTIALS;
 import static com.google.cloud.spanner.connection.ConnectionProperties.ENDPOINT;
+import static com.google.cloud.spanner.connection.ConnectionProperties.IS_EXPERIMENTAL_HOST;
 import static com.google.cloud.spanner.connection.ConnectionProperties.LENIENT;
 import static com.google.cloud.spanner.connection.ConnectionProperties.MAX_COMMIT_DELAY;
 import static com.google.cloud.spanner.connection.ConnectionProperties.MAX_PARTITIONED_PARALLELISM;
@@ -221,6 +222,7 @@ public String[] getValidValues() {
   private static final LocalConnectionChecker LOCAL_CONNECTION_CHECKER =
       new LocalConnectionChecker();
   static final boolean DEFAULT_USE_PLAIN_TEXT = false;
+  static final boolean DEFAULT_IS_EXPERIMENTAL_HOST = false;
   static final boolean DEFAULT_AUTOCOMMIT = true;
   static final boolean DEFAULT_READONLY = false;
   static final boolean DEFAULT_RETRY_ABORTS_INTERNALLY = true;
@@ -260,6 +262,8 @@ public String[] getValidValues() {
   static final boolean DEFAULT_AUTO_BATCH_DML = false;
   static final long DEFAULT_AUTO_BATCH_DML_UPDATE_COUNT = 1L;
   static final boolean DEFAULT_AUTO_BATCH_DML_UPDATE_COUNT_VERIFICATION = true;
+  private static final String EXPERIMENTAL_HOST_PROJECT_ID = "default";
+  private static final String DEFAULT_EXPERIMENTAL_HOST_INSTANCE_ID = "default";
 
   private static final String PLAIN_TEXT_PROTOCOL = "http:";
   private static final String HOST_PROTOCOL = "https:";
@@ -268,6 +272,8 @@ public String[] getValidValues() {
   private static final String DEFAULT_EMULATOR_HOST = "http://localhost:9010";
   /** Use plain text is only for local testing purposes. */
   static final String USE_PLAIN_TEXT_PROPERTY_NAME = "usePlainText";
+  /** Connect to a Experimental Host * */
+  static final String IS_EXPERIMENTAL_HOST_PROPERTY_NAME = "isExperimentalHost";
   /** Client certificate path to establish mTLS */
   static final String CLIENT_CERTIFICATE_PROPERTY_NAME = "clientCertificate";
   /** Client key path to establish mTLS */
@@ -444,6 +450,10 @@ static boolean isEnableTransactionalConnectionStateForPostgreSQL() {
                       USE_PLAIN_TEXT_PROPERTY_NAME,
                       "Use a plain text communication channel (i.e. non-TLS) for communicating with the server (true/false). Set this value to true for communication with the Cloud Spanner emulator.",
                       DEFAULT_USE_PLAIN_TEXT),
+                  ConnectionProperty.createBooleanProperty(
+                      IS_EXPERIMENTAL_HOST_PROPERTY_NAME,
+                      "Set this value to true for communication with an Experimental Host.",
+                      DEFAULT_IS_EXPERIMENTAL_HOST),
                   ConnectionProperty.createStringProperty(
                       CLIENT_CERTIFICATE_PROPERTY_NAME,
                       "Specifies the file path to the client certificate required for establishing an mTLS connection."),
@@ -664,7 +674,7 @@ private boolean isValidUri(String uri) {
       return SPANNER_URI_PATTERN.matcher(uri).matches();
     }
 
-    private boolean isValidExternalHostUri(String uri) {
+    private boolean isValidExperimentalHostUri(String uri) {
       return EXTERNAL_HOST_PATTERN.matcher(uri).matches();
     }
 
@@ -725,7 +735,7 @@ private boolean isValidExternalHostUri(String uri) {
      * @return this builder
      */
     public Builder setUri(String uri) {
-      if (!isValidExternalHostUri(uri)) {
+      if (!isValidExperimentalHostUri(uri)) {
         Preconditions.checkArgument(
             isValidUri(uri),
             "The specified URI is not a valid Cloud Spanner connection URI. Please specify a URI in the format \"cloudspanner:[//host[:port]]/projects/project-id[/instances/instance-id[/databases/database-name]][\\?property-name=property-value[;property-name=property-value]*]?\"");
@@ -857,10 +867,10 @@ public static Builder newBuilder() {
 
   private ConnectionOptions(Builder builder) {
     Matcher matcher;
-    boolean isExternalHost = false;
-    if (builder.isValidExternalHostUri(builder.uri)) {
+    boolean isExperimentalHostPattern = false;
+    if (builder.isValidExperimentalHostUri(builder.uri)) {
       matcher = Builder.EXTERNAL_HOST_PATTERN.matcher(builder.uri);
-      isExternalHost = true;
+      isExperimentalHostPattern = true;
     } else {
       matcher = Builder.SPANNER_URI_PATTERN.matcher(builder.uri);
     }
@@ -923,8 +933,8 @@ private ConnectionOptions(Builder builder) {
             getInitialConnectionPropertyValue(AUTO_CONFIG_EMULATOR),
             usePlainText,
             System.getenv());
-    GoogleCredentials defaultExternalHostCredentials =
-        SpannerOptions.getDefaultExternalHostCredentialsFromSysEnv();
+    GoogleCredentials defaultExperimentalHostCredentials =
+        SpannerOptions.getDefaultExperimentalCredentialsFromSysEnv();
     // Using credentials on a plain text connection is not allowed, so if the user has not specified
     // any credentials and is using a plain text connection, we should not try to get the
     // credentials from the environment, but default to NoCredentials.
@@ -939,8 +949,9 @@ && getInitialConnectionPropertyValue(OAUTH_TOKEN) == null
       this.credentials =
           new GoogleCredentials(
               new AccessToken(getInitialConnectionPropertyValue(OAUTH_TOKEN), null));
-    } else if (isExternalHost && defaultExternalHostCredentials != null) {
-      this.credentials = defaultExternalHostCredentials;
+    } else if ((isExperimentalHostPattern || isExperimentalHost())
+        && defaultExperimentalHostCredentials != null) {
+      this.credentials = defaultExperimentalHostCredentials;
     } else if (getInitialConnectionPropertyValue(CREDENTIALS_PROVIDER) != null) {
       try {
         this.credentials = getInitialConnectionPropertyValue(CREDENTIALS_PROVIDER).getCredentials();
@@ -981,16 +992,19 @@ && getInitialConnectionPropertyValue(OAUTH_TOKEN) == null
       this.sessionPoolOptions = sessionPoolOptionsBuilder.build();
     } else if (builder.sessionPoolOptions != null) {
       this.sessionPoolOptions = builder.sessionPoolOptions;
+    } else if (isExperimentalHostPattern || isExperimentalHost()) {
+      this.sessionPoolOptions =
+          SessionPoolOptions.newBuilder().setExperimentalHost().setAutoDetectDialect(true).build();
     } else {
       this.sessionPoolOptions = SessionPoolOptions.newBuilder().setAutoDetectDialect(true).build();
     }
 
-    String projectId = "default";
+    String projectId = EXPERIMENTAL_HOST_PROJECT_ID;
     String instanceId = matcher.group(Builder.INSTANCE_GROUP);
-    if (!isExternalHost) {
+    if (!isExperimentalHost() && !isExperimentalHostPattern) {
       projectId = matcher.group(Builder.PROJECT_GROUP);
-    } else if (instanceId == null) {
-      instanceId = "default";
+    } else if (instanceId == null && isExperimentalHost()) {
+      instanceId = DEFAULT_EXPERIMENTAL_HOST_INSTANCE_ID;
     }
     if (Builder.DEFAULT_PROJECT_ID_PLACEHOLDER.equalsIgnoreCase(projectId)) {
       projectId = getDefaultProjectId(this.credentials);
@@ -1311,6 +1325,10 @@ boolean isUsePlainText() {
         || getInitialConnectionPropertyValue(USE_PLAIN_TEXT);
   }
 
+  boolean isExperimentalHost() {
+    return getInitialConnectionPropertyValue(IS_EXPERIMENTAL_HOST);
+  }
+
   String getClientCertificate() {
     return getInitialConnectionPropertyValue(CLIENT_CERTIFICATE);
   }

google-cloud-spanner/src/main/java/com/google/cloud/spanner/connection/ConnectionProperties.java

@@ -47,6 +47,7 @@
 import static com.google.cloud.spanner.connection.ConnectionOptions.DEFAULT_ENABLE_END_TO_END_TRACING;
 import static com.google.cloud.spanner.connection.ConnectionOptions.DEFAULT_ENABLE_EXTENDED_TRACING;
 import static com.google.cloud.spanner.connection.ConnectionOptions.DEFAULT_ENDPOINT;
+import static com.google.cloud.spanner.connection.ConnectionOptions.DEFAULT_IS_EXPERIMENTAL_HOST;
 import static com.google.cloud.spanner.connection.ConnectionOptions.DEFAULT_KEEP_TRANSACTION_ALIVE;
 import static com.google.cloud.spanner.connection.ConnectionOptions.DEFAULT_LENIENT;
 import static com.google.cloud.spanner.connection.ConnectionOptions.DEFAULT_MAX_PARTITIONED_PARALLELISM;
@@ -76,6 +77,7 @@
 import static com.google.cloud.spanner.connection.ConnectionOptions.ENABLE_EXTENDED_TRACING_PROPERTY_NAME;
 import static com.google.cloud.spanner.connection.ConnectionOptions.ENCODED_CREDENTIALS_PROPERTY_NAME;
 import static com.google.cloud.spanner.connection.ConnectionOptions.ENDPOINT_PROPERTY_NAME;
+import static com.google.cloud.spanner.connection.ConnectionOptions.IS_EXPERIMENTAL_HOST_PROPERTY_NAME;
 import static com.google.cloud.spanner.connection.ConnectionOptions.KEEP_TRANSACTION_ALIVE_PROPERTY_NAME;
 import static com.google.cloud.spanner.connection.ConnectionOptions.LENIENT_PROPERTY_NAME;
 import static com.google.cloud.spanner.connection.ConnectionOptions.MAX_PARTITIONED_PARALLELISM_PROPERTY_NAME;
@@ -197,7 +199,14 @@ public class ConnectionProperties {
           BOOLEANS,
           BooleanConverter.INSTANCE,
           Context.STARTUP);
-
+  static final ConnectionProperty<Boolean> IS_EXPERIMENTAL_HOST =
+      create(
+          IS_EXPERIMENTAL_HOST_PROPERTY_NAME,
+          "Set this value to true for communication with a Experimental Host.",
+          DEFAULT_IS_EXPERIMENTAL_HOST,
+          BOOLEANS,
+          BooleanConverter.INSTANCE,
+          Context.STARTUP);
   static final ConnectionProperty<String> CLIENT_CERTIFICATE =
       create(
           CLIENT_CERTIFICATE_PROPERTY_NAME,