dimas-b commented on code in PR #3385:
URL: https://github.com/apache/polaris/pull/3385#discussion_r2828489335


##########
persistence/relational-jdbc/src/main/java/org/apache/polaris/persistence/relational/jdbc/JdbcMetricsPersistenceProducer.java:
##########
@@ -0,0 +1,148 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.polaris.persistence.relational.jdbc;
+
+import io.smallrye.common.annotation.Identifier;
+import jakarta.enterprise.context.ApplicationScoped;
+import jakarta.enterprise.context.RequestScoped;
+import jakarta.enterprise.inject.Instance;
+import jakarta.enterprise.inject.Produces;
+import jakarta.inject.Inject;
+import java.sql.SQLException;
+import javax.sql.DataSource;
+import org.apache.polaris.core.context.RealmContext;
+import org.apache.polaris.core.persistence.metrics.MetricsPersistence;
+import org.apache.polaris.core.persistence.metrics.MetricsSchemaBootstrap;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * CDI producer for {@link MetricsPersistence} in the JDBC persistence backend.
+ *
+ * <p>This producer creates {@link JdbcMetricsPersistence} instances when the 
JDBC persistence
+ * backend is in use. The schema version is loaded once at startup 
(application-scoped) to avoid
+ * hitting the database on every request.
+ *
+ * <p>When metrics tables are not available (metrics schema not bootstrapped), 
this producer returns
+ * {@link MetricsPersistence#NOOP} to avoid unnecessary database operations.
+ */
+@ApplicationScoped
+public class JdbcMetricsPersistenceProducer {
+
+  private static final Logger LOGGER =
+      LoggerFactory.getLogger(JdbcMetricsPersistenceProducer.class);
+
+  private final DatasourceOperations datasourceOperations;
+  private final boolean metricsSupported;
+
+  @SuppressWarnings("unused") // Required for CDI proxy
+  protected JdbcMetricsPersistenceProducer() {
+    this.datasourceOperations = null;
+    this.metricsSupported = false;
+  }
+
+  /**
+   * Creates the producer and determines metrics support at startup.
+   *
+   * <p>This constructor loads the metrics schema version once, avoiding 
database hits on every
+   * request. Metrics persistence is supported if the metrics_version table 
exists and contains a
+   * version >= 1.
+   *
+   * @param dataSource the datasource instance
+   * @param relationalJdbcConfiguration JDBC configuration
+   */
+  @Inject
+  public JdbcMetricsPersistenceProducer(
+      Instance<DataSource> dataSource, RelationalJdbcConfiguration 
relationalJdbcConfiguration) {
+    DatasourceOperations ops = null;
+    boolean supported = false;
+    try {
+      ops = new DatasourceOperations(dataSource.get(), 
relationalJdbcConfiguration);
+      // Check if metrics tables exist by querying the metrics_version table
+      supported = JdbcBasePersistenceImpl.metricsTableExists(ops);
+      if (!supported) {
+        LOGGER.warn(
+            "Metrics tables not found. Metrics persistence operations will be 
no-ops. "
+                + "Run 'bootstrap-metrics' command to create metrics tables or 
set "
+                + "polaris.persistence.metrics.type=noop to disable metrics 
persistence.");
+      }
+    } catch (SQLException e) {
+      LOGGER.warn(
+          "Failed to initialize JdbcMetricsPersistenceProducer due to {}. "
+              + "Metrics persistence will be disabled.",
+          e.getMessage());
+    }
+    this.datasourceOperations = ops;
+    this.metricsSupported = supported;
+  }
+
+  /**
+   * Produces a {@link MetricsPersistence} instance for the current request.
+   *
+   * <p>If metrics tables are not available (determined at startup), this 
returns {@link
+   * MetricsPersistence#NOOP}. Otherwise, it creates a {@link 
JdbcMetricsPersistence} configured
+   * with the current realm.
+   *
+   * <p>Note: We use {@code Instance<RealmContext>} instead of direct 
injection because {@link
+   * RealmContext} is only available in the service runtime context, not in 
the admin CLI context.
+   * Using {@code Instance} makes this a lazy/optional dependency that CDI 
won't validate at build
+   * time.
+   *
+   * @param realmContextInstance the realm context instance (lazy lookup)
+   * @return a MetricsPersistence implementation for JDBC, or NOOP if not 
supported
+   */
+  @Produces
+  @RequestScoped
+  @Identifier("relational-jdbc")
+  public MetricsPersistence metricsPersistence(Instance<RealmContext> 
realmContextInstance) {
+    if (!metricsSupported || datasourceOperations == null) {
+      return MetricsPersistence.NOOP;
+    }
+
+    if (realmContextInstance.isUnsatisfied()) {
+      LOGGER.warn(
+          "RealmContext not available. Returning NOOP MetricsPersistence. "
+              + "This is expected in CLI contexts.");

Review Comment:
   for follow-up: This is a bit odd... I believe `RealmContext` should always 
be available, but we can address it later.



##########
persistence/relational-jdbc/src/main/java/org/apache/polaris/persistence/relational/jdbc/JdbcBasePersistenceImpl.java:
##########
@@ -786,7 +787,8 @@ static boolean entityTableExists(DatasourceOperations 
datasourceOperations) {
   public static boolean metricsTableExists(DatasourceOperations 
datasourceOperations) {

Review Comment:
   Could we move this method to `JdbcMetricsPersistenceProducer`, which seems 
to be the only non-test caller?



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