Client config reporting — stage 2: full DRIVER_CONFIG report

core/src/main/java/com/datastax/oss/driver/api/core/config/DefaultDriverOption.java

@@ -1173,7 +1173,19 @@ public enum DefaultDriverOption implements DriverOption {
    *
    * <p>Value-Type: boolean
    */
-  ADDRESS_TRANSLATOR_RESOLVE_ADDRESSES("advanced.address-translator.resolve-addresses");
+  ADDRESS_TRANSLATOR_RESOLVE_ADDRESSES("advanced.address-translator.resolve-addresses"),
+  /**
+   * Whether the driver reports its effective client configuration to ScyllaDB at connection time.
+   *
+   * <p>When {@code true}, the driver sends a compact JSON description of its configuration in the
+   * CQL {@code STARTUP} options under the {@code DRIVER_CONFIG} key (control connection only);
+   * ScyllaDB stores it in {@code system.clients.client_options} so operators can inspect driver
+   * settings while investigating incidents. Independently of this flag, a {@code SESSION_ID}
+   * startup option is sent on every connection so the server can group a session's connections.
+   *
+   * <p>Value type: boolean
+   */
+  CLIENT_CONFIG_REPORTING_ENABLED("advanced.client-config-reporting.enabled");
 
   private final String path;
 

core/src/main/java/com/datastax/oss/driver/api/core/config/OptionsMap.java

@@ -400,6 +400,7 @@ protected static void fillWithDriverDefaults(OptionsMap map) {
     // values) with no sensible scalar default, analogous to how CONFIG_RELOAD_INTERVAL is omitted.
     map.put(TypedDriverOption.CLIENT_ROUTES_NATIVE_TRANSPORT_PORT, 9042);
     map.put(TypedDriverOption.CLIENT_ROUTES_SHARD_AWARENESS_ENABLED, false);
+    map.put(TypedDriverOption.CLIENT_CONFIG_REPORTING_ENABLED, false);
   }
 
   @Immutable

core/src/main/java/com/datastax/oss/driver/api/core/config/TypedDriverOption.java

@@ -976,6 +976,11 @@ public String toString() {
       new TypedDriverOption<>(
           DefaultDriverOption.CLIENT_ROUTES_SHARD_AWARENESS_ENABLED, GenericType.BOOLEAN);
 
+  /** Whether the driver reports its client configuration to ScyllaDB at connection time. */
+  public static final TypedDriverOption<Boolean> CLIENT_CONFIG_REPORTING_ENABLED =
+      new TypedDriverOption<>(
+          DefaultDriverOption.CLIENT_CONFIG_REPORTING_ENABLED, GenericType.BOOLEAN);
+
   private static Iterable<TypedDriverOption<?>> introspectBuiltInValues() {
     try {
       ImmutableList.Builder<TypedDriverOption<?>> result = ImmutableList.builder();

core/src/main/java/com/datastax/oss/driver/internal/core/channel/DriverChannelOptions.java

@@ -47,22 +47,32 @@ public static Builder builder() {
 
   public final String ownerLogPrefix;
 
+  /**
+   * Whether the channel should report the driver configuration ({@code DRIVER_CONFIG}) in its
+   * {@code STARTUP} options. Set only for the control connection, so the (potentially large) config
+   * blob is sent once per session rather than on every pooled connection.
+   */
+  public final boolean reportConfig;
+
   private DriverChannelOptions(
       CqlIdentifier keyspace,
       List<String> eventTypes,
       EventCallback eventCallback,
-      String ownerLogPrefix) {
+      String ownerLogPrefix,
+      boolean reportConfig) {
     this.keyspace = keyspace;
     this.eventTypes = eventTypes;
     this.eventCallback = eventCallback;
     this.ownerLogPrefix = ownerLogPrefix;
+    this.reportConfig = reportConfig;
   }
 
   public static class Builder {
     private CqlIdentifier keyspace = null;
     private List<String> eventTypes = Collections.emptyList();
     private EventCallback eventCallback = null;
     private String ownerLogPrefix = null;
+    private boolean reportConfig = false;
 
     public Builder withKeyspace(CqlIdentifier keyspace) {
       this.keyspace = keyspace;
@@ -82,8 +92,17 @@ public Builder withOwnerLogPrefix(String ownerLogPrefix) {
       return this;
     }
 
+    /**
+     * Marks this channel as the one that reports {@code DRIVER_CONFIG} (the control connection).
+     */
+    public Builder reportConfig(boolean reportConfig) {
+      this.reportConfig = reportConfig;
+      return this;
+    }
+
     public DriverChannelOptions build() {
-      return new DriverChannelOptions(keyspace, eventTypes, eventCallback, ownerLogPrefix);
+      return new DriverChannelOptions(
+          keyspace, eventTypes, eventCallback, ownerLogPrefix, reportConfig);
     }
   }
 }

core/src/main/java/com/datastax/oss/driver/internal/core/channel/ProtocolInitHandler.java

@@ -194,6 +194,11 @@ Message getRequest() {
           if (featureStore != null) {
             featureStore.populateStartupOptions(startupOptions);
           }
+          // Adds SESSION_ID on every connection and DRIVER_CONFIG on the control connection
+          // (options.reportConfig); no-op when client config reporting is disabled.
+          context
+              .getDriverConfigReporter()
+              .populateStartupOptions(startupOptions, options.reportConfig);
           return request = new Startup(startupOptions);
         case GET_CLUSTER_NAME:
           return request = CLUSTER_NAME_QUERY;