Make ImmutablePluginConfigVariable.refresh() a no-op instead of throwing.

The refresh() method semantically means "re-read from your backing store." For an immutable variable with no backing store, this is naturally a no-op. Only setValue() should throw since it attempts to mutate the value. This allows callers to safely call refresh() without needing to guard with isUpdatable() checks.

Signed-off-by: David Venable <dlv@amazon.com>

Author: dlvenable

data-prepper-api/src/main/java/org/opensearch/dataprepper/model/plugin/PluginConfigVariable.java

@@ -31,12 +31,17 @@ public interface PluginConfigVariable {
     void setValue(Object updatedValue);
 
     /**
-     * Refresh the secret value on demand
+     * Refresh the secret value on demand.
+     * <p>
+     * This call semantically means to refresh the value from the underlying data store. If that
+     * is not supported an implementation should perform a no-op.
      */
     void refresh();
 
     /**
-     * Returns if the variable is updatable.
+     * Returns if the variable is updatable from Data Prepper itself. This indicates
+     * that Data Prepper itself can update the actual value, not that the value itself can be
+     * updated from another system.
      *
      * @return true if this variable is updatable, false otherwise
      */

data-prepper-plugin-framework/src/main/java/org/opensearch/dataprepper/plugin/VariableExpander.java

@@ -90,8 +90,6 @@ public void setValue(Object updatedValue) {
 
         @Override
         public void refresh() {
-            // No-op as this is immutable
-            throw new UnsupportedOperationException("ImmutablePluginConfigVariable doesn't support this operation");
         }
 
         @Override

data-prepper-plugin-framework/src/test/java/org/opensearch/dataprepper/plugin/VariableExpanderTest.java

@@ -195,6 +195,29 @@ void testTranslateJsonParserWithSPluginConfigVariableValue_when_non_secret_forma
         assertFalse(pluginConfigVariableInstance.isUpdatable());
     }
 
+    @Test
+    void testImmutablePluginConfigVariable_refresh_does_not_throw() throws IOException {
+        final String testSecretReference = UUID.randomUUID().toString();
+        final JsonParser jsonParser = JSON_FACTORY.createParser(String.format("\"%s\"", testSecretReference));
+        jsonParser.nextToken();
+        objectUnderTest = new VariableExpander(OBJECT_MAPPER, Set.of(pluginConfigValueTranslator));
+        final Object actualResult = objectUnderTest.translate(jsonParser, PluginConfigVariable.class);
+        PluginConfigVariable pluginConfigVariableInstance = (PluginConfigVariable) actualResult;
+        pluginConfigVariableInstance.refresh();
+        assertThat(pluginConfigVariableInstance.getValue().toString(), equalTo(testSecretReference));
+    }
+
+    @Test
+    void testImmutablePluginConfigVariable_setValue_throws() throws IOException {
+        final String testSecretReference = UUID.randomUUID().toString();
+        final JsonParser jsonParser = JSON_FACTORY.createParser(String.format("\"%s\"", testSecretReference));
+        jsonParser.nextToken();
+        objectUnderTest = new VariableExpander(OBJECT_MAPPER, Set.of(pluginConfigValueTranslator));
+        final Object actualResult = objectUnderTest.translate(jsonParser, PluginConfigVariable.class);
+        PluginConfigVariable pluginConfigVariableInstance = (PluginConfigVariable) actualResult;
+        assertThrows(UnsupportedOperationException.class, () -> pluginConfigVariableInstance.setValue("new-value"));
+    }
+
     @Test
     void testTranslateJsonParserWithSPluginConfigVariableValue_translate_failure() throws IOException {
         final String testSecretKey = "testSecretKey";