[GitHub] [beam] apilloud commented on a change in pull request #13629: [BEAM-10925] Load SQL UDFs from jar.

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

apilloud commented on a change in pull request #13629:
URL: https://github.com/apache/beam/pull/13629#discussion_r549559876



##########
File path: sdks/java/extensions/sql/src/main/java/org/apache/beam/sdk/extensions/sql/impl/JavaUdfLoader.java
##########
@@ -0,0 +1,206 @@
+/*
+ * 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.beam.sdk.extensions.sql.impl;
+
+import com.google.auto.value.AutoValue;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.nio.channels.ReadableByteChannel;
+import java.nio.channels.WritableByteChannel;
+import java.nio.file.ProviderNotFoundException;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.ServiceLoader;
+import org.apache.beam.sdk.extensions.sql.udf.ScalarFn;
+import org.apache.beam.sdk.extensions.sql.udf.UdfProvider;
+import org.apache.beam.sdk.io.FileSystems;
+import org.apache.beam.sdk.io.fs.ResourceId;
+import org.apache.beam.sdk.util.common.ReflectHelpers;
+import org.apache.beam.vendor.calcite.v1_20_0.org.apache.commons.codec.digest.DigestUtils;
+import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.annotations.VisibleForTesting;
+import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions;
+import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.collect.ImmutableList;
+import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.collect.ImmutableMap;
+import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.io.ByteStreams;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Loads {@link UdfProvider} implementations from user-provided jars.
+ *
+ * <p>All UDFs are loaded and cached for each jar to mitigate IO costs.
+ */
+public class JavaUdfLoader {
+  private static final Logger LOG = LoggerFactory.getLogger(JavaUdfLoader.class);
+
+  /**
+   * Maps the external jar location to the functions the jar defines. Static so it can persist
+   * across multiple SQL transforms.
+   */
+  private static final Map<String, FunctionDefinitions> cache = new HashMap<>();
+
+  private static final ClassLoader originalClassLoader = ReflectHelpers.findClassLoader();
+
+  /**
+   * Load a user-defined scalar function from the specified jar.
+   *
+   * <p><strong>WARNING</strong>: The first time a jar is loaded, it is added to the thread's
+   * context {@link ClassLoader} so that the jar can be staged by the runner.
+   */
+  public ScalarFn loadScalarFunction(List<String> functionPath, String jarPath) {
+    String functionFullName = String.join(".", functionPath);
+    try {
+      FunctionDefinitions functionDefinitions = loadJar(jarPath);
+      if (!functionDefinitions.scalarFunctions().containsKey(functionPath)) {
+        throw new IllegalArgumentException(
+            String.format(
+                "No implementation of scalar function %s found in %s.%n"
+                    + " 1. Create a class implementing %s and annotate it with @AutoService(%s.class).%n"
+                    + " 2. Add function %s to the class's userDefinedScalarFunctions implementation.",
+                functionFullName,
+                jarPath,
+                UdfProvider.class.getSimpleName(),
+                UdfProvider.class.getSimpleName(),
+                functionFullName));
+      }
+      return functionDefinitions.scalarFunctions().get(functionPath);
+    } catch (IOException e) {
+      throw new RuntimeException(
+          String.format(
+              "Failed to load user-defined scalar function %s from %s", functionFullName, jarPath),
+          e);
+    }
+  }
+
+  /**
+   * Creates a temporary local copy of the file at {@code inputPath}, and returns a handle to the
+   * local copy.
+   */
+  private File downloadFile(String inputPath, String mimeType) throws IOException {
+    Preconditions.checkArgument(!inputPath.isEmpty(), "Path cannot be empty.");
+    ResourceId inputResource = FileSystems.matchNewResource(inputPath, false /* is directory */);
+    try (ReadableByteChannel inputChannel = FileSystems.open(inputResource)) {
+      File outputFile = File.createTempFile("sql-udf-", inputResource.getFilename());
+      ResourceId outputResource =
+          FileSystems.matchNewResource(outputFile.getAbsolutePath(), false /* is directory */);
+      try (WritableByteChannel outputChannel = FileSystems.create(outputResource, mimeType)) {
+        ByteStreams.copy(inputChannel, outputChannel);
+      }
+      // Compute and log checksum.
+      try (InputStream inputStream = new FileInputStream(outputFile)) {
+        LOG.info(
+            "Copied {} to {} with md5 hash {}.",
+            inputPath,
+            outputFile.getAbsolutePath(),
+            DigestUtils.md5Hex(inputStream));
+      }
+      return outputFile;
+    }
+  }
+
+  private ClassLoader createAndSetClassLoader(String inputJarPath) throws IOException {
+    File tmpJar = downloadFile(inputJarPath, "application/java-archive");
+    // Set the thread's context class loader so that the jar can be staged by the runner.
+    Thread.currentThread()
+        .setContextClassLoader(

Review comment:
       You've leaked the class loader here. setContextClassLoader should always be inside a try finally block that resets the class loader. For example: https://github.com/apache/beam/blob/3bb232fb098700de408f574585dfe74bbaff7230/sdks/java/extensions/sql/src/main/java/org/apache/beam/sdk/extensions/sql/impl/rel/BeamEnumerableConverter.java#L118




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