[GitHub] [incubator-pinot] fx19880617 commented on a change in pull request #6271: Adding config utils to apply environment variables and apply it to table config

[GitBox <gi...@apache.org>]

fx19880617 commented on a change in pull request #6271:
URL: https://github.com/apache/incubator-pinot/pull/6271#discussion_r525429748



##########
File path: pinot-spi/src/main/java/org/apache/pinot/spi/config/ConfigUtils.java
##########
@@ -0,0 +1,90 @@
+/**
+ * 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.pinot.spi.config;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.node.ArrayNode;
+import com.fasterxml.jackson.databind.node.JsonNodeFactory;
+import com.fasterxml.jackson.databind.node.JsonNodeType;
+import java.io.IOException;
+import java.util.Iterator;
+import java.util.Map;
+import org.apache.pinot.spi.utils.JsonUtils;
+
+
+public class ConfigUtils {
+  private static final Map<String, String> ENVIRONMENT_VARIABLES = System.getenv();
+
+  /**
+   * Apply environment variables to any given BaseJsonConfig.
+   *
+   * @return Config with environment variable applied.
+   */
+  public static <T extends BaseJsonConfig> T applyConfigWithEnvVariables(T config) {
+    JsonNode jsonNode;
+    try {
+      jsonNode = applyConfigWithEnvVariables(config.toJsonNode());
+    } catch (RuntimeException e) {
+      throw new RuntimeException(String
+          .format("Unable to apply environment variables on json config class [%s].", config.getClass().getName()), e);
+    }
+    try {
+      return (T) JsonUtils.jsonNodeToObject(jsonNode, config.getClass());
+    } catch (IOException e) {
+      throw new RuntimeException(String
+          .format("Unable to read JsonConfig to class [%s] after applying environment variables, jsonConfig is: '%s'.",
+              config.getClass().getName(), jsonNode.toString()), e);
+    }
+  }
+
+  private static JsonNode applyConfigWithEnvVariables(JsonNode jsonNode) {
+    final JsonNodeType nodeType = jsonNode.getNodeType();
+    switch (nodeType) {
+      case OBJECT:
+        if (jsonNode.size() > 0) {
+          Iterator<Map.Entry<String, JsonNode>> iterator = jsonNode.fields();
+          while (iterator.hasNext()) {
+            final Map.Entry<String, JsonNode> next = iterator.next();
+            next.setValue(applyConfigWithEnvVariables(next.getValue()));
+          }
+        }
+        break;
+      case ARRAY:
+        if (jsonNode.isArray()) {
+          ArrayNode arrayNode = (ArrayNode) jsonNode;
+          for (int i = 0; i < arrayNode.size(); i++) {
+            JsonNode arrayElement = arrayNode.get(i);
+            arrayNode.set(i, applyConfigWithEnvVariables(arrayElement));
+          }
+        }
+        break;
+      case STRING:
+        final String field = jsonNode.asText();
+        if (field.startsWith("${") && field.endsWith("}")) {
+          final String envVarKey = field.substring(2, field.length() - 1);
+          if (ENVIRONMENT_VARIABLES.containsKey(envVarKey)) {

Review comment:
       The names of environment variables are case-sensitive; by convention they are uppercase, so technically you can define env var: `a` and `A` with different values.




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