add config value override via cli args

packages/kbn-apm-config-loader/src/config_loader.ts

@@ -17,7 +17,7 @@
  * under the License.
  */
 
-import { getConfigurationFilePaths, getConfigFromFiles } from './utils';
+import { getConfigurationFilePaths, getConfigFromFiles, applyConfigOverrides } from './utils';
 
 import { ApmConfiguration } from './config';
 
@@ -30,5 +30,6 @@ import { ApmConfiguration } from './config';
 export const loadConfiguration = (argv: string[], rootDir: string): ApmConfiguration => {
   const configPaths = getConfigurationFilePaths(argv);
   const rawConfiguration = getConfigFromFiles(configPaths);
+  applyConfigOverrides(rawConfiguration, argv);
   return new ApmConfiguration(rootDir, rawConfiguration);
 };

packages/kbn-apm-config-loader/src/utils/apply_config_overrides.ts

@@ -0,0 +1,38 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. 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.
+ */
+
+import { set } from '@elastic/safer-lodash-set';
+import { getFlagValue } from './read_argv';
+
+/**
+ * Manually applies the specific configuration overrides we need to load the APM config.
+ * Currently, only these are needed:
+ *   - server.uuid
+ *   - path.data
+ */
+export const applyConfigOverrides = (config: Record<string, any>, argv: string[]) => {
+  const serverUuid = getFlagValue(argv, '--server.uuid');
+  if (serverUuid) {
+    set(config, 'server.uuid', serverUuid);
+  }
+  const dataPath = getFlagValue(argv, '--path.data');
+  if (dataPath) {
+    set(config, 'path.data', dataPath);
+  }
+};

packages/kbn-apm-config-loader/src/utils/index.ts

@@ -19,3 +19,4 @@
 
 export { getConfigFromFiles } from './read_config';
 export { getConfigurationFilePaths } from './get_config_file_paths';
+export { applyConfigOverrides } from './apply_config_overrides';

packages/kbn-apm-config-loader/src/utils/read_config.ts

@@ -50,8 +50,8 @@ function merge(target: Record<string, any>, value: any, key?: string) {
 }
 
 /** @internal */
-export const getConfigFromFiles = (configFiles: readonly string[]) => {
-  let mergedYaml = {};
+export const getConfigFromFiles = (configFiles: readonly string[]): Record<string, any> => {
+  let mergedYaml: Record<string, any> = {};
 
   for (const configFile of configFiles) {
     const yaml = readYaml(configFile);