KAFKA-15031: Add plugin.discovery to Connect worker configuration (KIP-898)

connect/api/src/main/resources/META-INF/services/org.apache.kafka.connect.storage.Converter

@@ -0,0 +1,16 @@
+ # 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.
+
+org.apache.kafka.connect.storage.StringConverter

connect/api/src/main/resources/META-INF/services/org.apache.kafka.connect.storage.HeaderConverter

@@ -0,0 +1,17 @@
+ # 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.
+
+org.apache.kafka.connect.storage.SimpleHeaderConverter
+org.apache.kafka.connect.storage.StringConverter

connect/api/src/test/resources/META-INF/services/org.apache.kafka.connect.sink.SinkConnector

@@ -0,0 +1,16 @@
+ # 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.
+
+org.apache.kafka.connect.sink.SinkConnectorTest$TestSinkConnector

connect/api/src/test/resources/META-INF/services/org.apache.kafka.connect.source.SourceConnector

@@ -0,0 +1,16 @@
+ # 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.
+
+org.apache.kafka.connect.source.SourceConnectorTest$TestSourceConnector

connect/file/src/main/resources/META-INF/services/org.apache.kafka.connect.sink.SinkConnector

@@ -0,0 +1,16 @@
+ # 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.
+
+org.apache.kafka.connect.file.FileStreamSinkConnector

connect/file/src/main/resources/META-INF/services/org.apache.kafka.connect.source.SourceConnector

@@ -0,0 +1,16 @@
+ # 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.
+
+org.apache.kafka.connect.file.FileStreamSourceConnector

connect/json/src/main/resources/META-INF/services/org.apache.kafka.connect.storage.Converter

@@ -0,0 +1,16 @@
+ # 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.
+
+org.apache.kafka.connect.json.JsonConverter

connect/json/src/main/resources/META-INF/services/org.apache.kafka.connect.storage.HeaderConverter

@@ -0,0 +1,16 @@
+ # 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.
+
+org.apache.kafka.connect.json.JsonConverter

connect/mirror/src/main/resources/META-INF/services/org.apache.kafka.connect.source.SourceConnector

@@ -0,0 +1,18 @@
+ # 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.
+
+org.apache.kafka.connect.mirror.MirrorCheckpointConnector
+org.apache.kafka.connect.mirror.MirrorHeartbeatConnector
+org.apache.kafka.connect.mirror.MirrorSourceConnector

connect/runtime/src/main/java/org/apache/kafka/connect/runtime/WorkerConfig.java

@@ -25,7 +25,9 @@
 import org.apache.kafka.common.config.ConfigDef.Importance;
 import org.apache.kafka.common.config.ConfigDef.Type;
 import org.apache.kafka.common.metrics.Sensor;
+import org.apache.kafka.common.utils.Utils;
 import org.apache.kafka.connect.errors.ConnectException;
+import org.apache.kafka.connect.runtime.isolation.PluginDiscoveryMode;
 import org.apache.kafka.connect.runtime.rest.RestServerConfig;
 import org.apache.kafka.connect.storage.SimpleHeaderConverter;
 import org.slf4j.Logger;
@@ -35,13 +37,18 @@
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Objects;
 import java.util.concurrent.ExecutionException;
 
 import static org.apache.kafka.common.config.ConfigDef.Range.atLeast;
 import static org.apache.kafka.common.config.ConfigDef.ValidString.in;
 import static org.apache.kafka.connect.runtime.SourceConnectorConfig.TOPIC_CREATION_PREFIX;
+import static org.apache.kafka.connect.runtime.isolation.PluginDiscoveryMode.ONLY_SCAN;
+import static org.apache.kafka.connect.runtime.isolation.PluginDiscoveryMode.HYBRID_WARN;
+import static org.apache.kafka.connect.runtime.isolation.PluginDiscoveryMode.HYBRID_FAIL;
+import static org.apache.kafka.connect.runtime.isolation.PluginDiscoveryMode.SERVICE_LOAD;
 
 /**
  * Common base class providing configuration for Kafka Connect workers, whether standalone or distributed.
@@ -122,6 +129,18 @@ public class WorkerConfig extends AbstractConfig {
             + "by the worker's scanner before config providers are initialized and used to "
             + "replace variables.";
 
+    public static final String PLUGIN_DISCOVERY_CONFIG = "plugin.discovery";
+    protected static final String PLUGIN_DISCOVERY_DOC = "Method to use to discover plugins present in the classpath "
+            + "and plugin.path configuration. This can be one of multiple values with the following meanings:\n"
+            + "* " + ONLY_SCAN.name() + ": Discover plugins only by reflection. "
+            + "Plugins which are not discoverable by ServiceLoader will not impact worker startup.\n"
+            + "* " + HYBRID_WARN.name() + ": Discover plugins reflectively and by ServiceLoader. "
+            + "Plugins which are not discoverable by ServiceLoader will print warnings during worker startup.\n"
+            + "* " + HYBRID_FAIL.name() + ": Discover plugins reflectively and by ServiceLoader. "
+            + "Plugins which are not discoverable by ServiceLoader will cause worker startup to fail.\n"
+            + "* " + SERVICE_LOAD.name() + ": Discover plugins only by ServiceLoader. Faster startup than other modes. "
+            + "Plugins which are not discoverable by ServiceLoader may not be usable.";
+
     public static final String CONFIG_PROVIDERS_CONFIG = "config.providers";
     protected static final String CONFIG_PROVIDERS_DOC =
             "Comma-separated names of <code>ConfigProvider</code> classes, loaded and used "
@@ -199,6 +218,12 @@ protected static ConfigDef baseConfigDef() {
                         null,
                         Importance.LOW,
                         PLUGIN_PATH_DOC)
+                .define(PLUGIN_DISCOVERY_CONFIG,
+                        Type.STRING,
+                        PluginDiscoveryMode.HYBRID_WARN.toString(),
+                        ConfigDef.CaseInsensitiveValidString.in(Utils.enumOptions(PluginDiscoveryMode.class)),
+                        Importance.LOW,
+                        PLUGIN_DISCOVERY_DOC)
                 .define(METRICS_SAMPLE_WINDOW_MS_CONFIG, Type.LONG,
                         30000, atLeast(0), Importance.LOW,
                         CommonClientConfigs.METRICS_SAMPLE_WINDOW_MS_DOC)
@@ -401,6 +426,16 @@ public static String pluginPath(Map<String, String> props) {
         return props.get(WorkerConfig.PLUGIN_PATH_CONFIG);
     }
 
+    public static PluginDiscoveryMode pluginDiscovery(Map<String, String> props) {
+        String value = props.getOrDefault(WorkerConfig.PLUGIN_DISCOVERY_CONFIG, PluginDiscoveryMode.HYBRID_WARN.toString());
+        try {
+            return PluginDiscoveryMode.valueOf(value.toUpperCase(Locale.ROOT));
+        } catch (IllegalArgumentException e) {
+            throw new ConnectException("Invalid " + PLUGIN_DISCOVERY_CONFIG + " value, must be one of "
+                    + Arrays.toString(Utils.enumOptions(PluginDiscoveryMode.class)));
+        }
+    }
+
     public WorkerConfig(ConfigDef definition, Map<String, String> props) {
         super(definition, props);
         logInternalConverterRemovalWarnings(props);

connect/runtime/src/main/java/org/apache/kafka/connect/runtime/isolation/PluginDiscoveryMode.java

@@ -0,0 +1,58 @@
+/*
+ * 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.kafka.connect.runtime.isolation;
+
+/**
+ * Strategy to use to discover plugins usable on a Connect worker.
+ * @see <a href="https://cwiki.apache.org/confluence/display/KAFKA/KIP-898%3A+Modernize+Connect+plugin+discovery">KIP-898</a>
+ */
+public enum PluginDiscoveryMode {
+
+    /**
+     * Scan for plugins reflectively. This corresponds to the legacy behavior of Connect prior to KIP-898.
+     * <p>Note: the following plugins are still loaded using {@link java.util.ServiceLoader} in this mode:
+     * <ul>
+     *     <li>{@link org.apache.kafka.common.config.provider.ConfigProvider}</li>
+     *     <li>{@link org.apache.kafka.connect.rest.ConnectRestExtension}</li>
+     *     <li>{@link org.apache.kafka.connect.connector.policy.ConnectorClientConfigOverridePolicy}</li>
+     * </ul>
+     */
+    ONLY_SCAN,
+    /**
+     * Scan for plugins reflectively and via {@link java.util.ServiceLoader}.
+     * Emit warnings if one or more plugins is not available via {@link java.util.ServiceLoader}
+     */
+    HYBRID_WARN,
+    /**
+     * Scan for plugins reflectively and via {@link java.util.ServiceLoader}.
+     * Fail worker during startup if one or more plugins is not available via {@link java.util.ServiceLoader}
+     */
+    HYBRID_FAIL,
+    /**
+     * Discover plugins via {@link java.util.ServiceLoader} only.
+     * Plugins will not be present in the REST API if they are not available via {@link java.util.ServiceLoader}
+     */
+    SERVICE_LOAD;
+
+    public boolean reflectivelyScan() {
+        return this != SERVICE_LOAD;
+    }
+
+    public boolean serviceLoad() {
+        return this != ONLY_SCAN;
+    }
+}