[GitHub] [iceberg] yyanyy commented on a change in pull request #2146: Improved error messages in CatalogUtil.loadCatalog

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

yyanyy commented on a change in pull request #2146:
URL: https://github.com/apache/iceberg/pull/2146#discussion_r564199952



##########
File path: core/src/test/java/org/apache/iceberg/TestCatalogUtil.java
##########
@@ -87,6 +87,32 @@ public void loadCustomCatalog_NotImplementCatalog() {
         () -> CatalogUtil.loadCatalog(TestCatalogNoInterface.class.getName(), name, options, hadoopConf));
   }
 
+  @Test
+  public void loadCustomCatalog_ConstructorErrorCatalog() {
+    Map<String, String> options = new HashMap<>();
+    options.put("key", "val");
+    Configuration hadoopConf = new Configuration();
+    String name = "custom";
+
+    String impl = TestCatalogErrorConstructor.class.getName();
+    AssertHelpers.assertThrows("must be able to initialize catalog",

Review comment:
       Nit: "must not be able to"? 

##########
File path: core/src/main/java/org/apache/iceberg/CatalogUtil.java
##########
@@ -129,6 +129,35 @@ private static void deleteFiles(FileIO io, Set<ManifestFile> allManifests) {
         });
   }
 
+  /**
+   * Get constructor for Catalog from impl. Impl must be valid class name and have zero-arg constructor.
+   *
+   * <p>We try to get the constructor for impl and if we fail we check for common error patterns. Specifically:
+   * a ClassNotFoundException for an invalid impl String and a NoClassDefFoundError if impl fails to get initialized.
+   * Otherwise the original exception is passed up and the error is assumed to be a missing no-args constructor.
+   *
+   * @param impl catalog implementation full class name
+   * @return constructor for catalog implementation impl
+   * @throws IllegalArgumentException if no-arg constructor not found or error during initialization
+   */
+  private static DynConstructors.Ctor<Catalog> getCatalogConstructor(String impl) {
+    DynConstructors.Ctor<Catalog> ctor;
+    DynConstructors.Builder ctorBuilder = DynConstructors.builder(Catalog.class).impl(impl);
+    try {
+      ctor = ctorBuilder.buildChecked();
+    } catch (NoSuchMethodException e) {
+      Throwable originalError = ctorBuilder.problems().getOrDefault(impl, e);
+      String message = String.format("Cannot initialize Catalog, missing no-arg constructor: %s", impl);

Review comment:
       Nit: "Cannot initialize Catalog" will be printed twice if the error is neither of the one below. Although I wonder if there's a specific exception thrown if the catalog class can be found but does not have a no-arg constructor, and if so we probably could catch and print that instead, since I'd suspect the chance of misconfiguring could be much larger than only missing the no-arg constructor itself, and hence "cannot be initialized" might be a better default ... 




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