Github user JPercivall commented on a diff in the pull request:
https://github.com/apache/nifi/pull/525#discussion_r67437336
--- Diff:
nifi-nar-bundles/nifi-windows-event-log-bundle/nifi-windows-event-log-processors/src/main/java/org/apache/nifi/processors/windows/event/log/EvtSubscribe.java
---
@@ -0,0 +1,272 @@
+/*
+ * 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.nifi.processors.windows.event.log;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.net.MediaType;
+import com.sun.jna.platform.win32.Kernel32;
+import com.sun.jna.platform.win32.WinNT;
+import org.apache.commons.io.Charsets;
+import org.apache.nifi.annotation.behavior.InputRequirement;
+import org.apache.nifi.annotation.behavior.WritesAttribute;
+import org.apache.nifi.annotation.behavior.WritesAttributes;
+import org.apache.nifi.annotation.documentation.CapabilityDescription;
+import org.apache.nifi.annotation.documentation.Tags;
+import org.apache.nifi.annotation.lifecycle.OnScheduled;
+import org.apache.nifi.annotation.lifecycle.OnStopped;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.components.ValidationContext;
+import org.apache.nifi.components.ValidationResult;
+import org.apache.nifi.flowfile.FlowFile;
+import org.apache.nifi.flowfile.attributes.CoreAttributes;
+import org.apache.nifi.processor.AbstractSessionFactoryProcessor;
+import org.apache.nifi.processor.ProcessContext;
+import org.apache.nifi.processor.ProcessSession;
+import org.apache.nifi.processor.ProcessSessionFactory;
+import org.apache.nifi.processor.Relationship;
+import org.apache.nifi.processor.exception.ProcessException;
+import org.apache.nifi.processor.util.StandardValidators;
+import
org.apache.nifi.processors.windows.event.log.jna.EventSubscribeXmlRenderingCallback;
+import org.apache.nifi.processors.windows.event.log.jna.WEvtApi;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Queue;
+import java.util.Set;
+import java.util.concurrent.atomic.AtomicReference;
+
+
+@InputRequirement(InputRequirement.Requirement.INPUT_FORBIDDEN)
+@Tags({"ingest", "event", "windows"})
+@CapabilityDescription("Registers a Windows Event Log Subscribe Callback
to receive FlowFiles from Events on Windows. These can be filtered via channel
and XPath.")
+@WritesAttributes({
+ @WritesAttribute(attribute = "mime.type", description = "Will set
a MIME type value of application/xml.")
+})
+public class EvtSubscribe extends AbstractSessionFactoryProcessor {
+ public static final String DEFAULT_CHANNEL = "System";
+ public static final String DEFAULT_XPATH = "*";
+ public static final int DEFAULT_MAX_BUFFER = 1024 * 1024;
+ public static final int DEFAULT_MAX_QUEUE_SIZE = 1024;
+
+ public static final PropertyDescriptor CHANNEL = new
PropertyDescriptor.Builder()
+ .name("channel")
+ .displayName("Channel")
+ .required(true)
+ .defaultValue(DEFAULT_CHANNEL)
+ .description("The Windows Event Log Channel to listen to.")
+ .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
+ .build();
+
+ public static final PropertyDescriptor QUERY = new
PropertyDescriptor.Builder()
+ .name("query")
+ .displayName("XPath Query")
+ .required(true)
+ .defaultValue(DEFAULT_XPATH)
+ .description("XPath Query to filter events. (See
https://msdn.microsoft.com/en-us/library/windows/desktop/dd996910(v=vs.85).aspx
for examples.)")
+ .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
+ .build();
+
+ public static final PropertyDescriptor MAX_BUFFER_SIZE = new
PropertyDescriptor.Builder()
+ .name("maxBuffer")
+ .displayName("Maximum Buffer Size")
+ .required(true)
+ .defaultValue(Integer.toString(DEFAULT_MAX_BUFFER))
+ .description("The individual Event Log XMLs are rendered to a
buffer." +
+ " This specifies the maximum size in bytes that the
buffer will be allowed to grow to. (Limiting the maximum size of an individual
Event XML.)")
+ .addValidator(StandardValidators.POSITIVE_INTEGER_VALIDATOR)
+ .build();
+
+ public static final PropertyDescriptor MAX_EVENT_QUEUE_SIZE = new
PropertyDescriptor.Builder()
+ .name("maxQueue")
+ .displayName("Maximum queue size")
+ .required(true)
+ .defaultValue(Integer.toString(DEFAULT_MAX_QUEUE_SIZE))
+ .description("Maximum number of events to queue for
transformation into FlowFiles before the Processor starts running.")
+ .addValidator(StandardValidators.POSITIVE_INTEGER_VALIDATOR)
+ .build();
+
+ public static final List<PropertyDescriptor> PROPERTY_DESCRIPTORS =
Collections.unmodifiableList(Arrays.asList(CHANNEL, QUERY, MAX_BUFFER_SIZE,
MAX_EVENT_QUEUE_SIZE));
+
+ public static final Relationship REL_SUCCESS = new
Relationship.Builder()
+ .name("success")
+ .description("Relationship for successfully formatted events.")
+ .build();
+
+ public static final Set<Relationship> RELATIONSHIPS =
Collections.unmodifiableSet(new HashSet<>(Arrays.asList(REL_SUCCESS)));
+
+ private final AtomicReference<ProcessSessionFactory>
sessionFactoryReference;
+ private final Queue<String> renderedXMLs;
+ private final WEvtApi wEvtApi;
+ private final Kernel32 kernel32;
+
+ private Throwable wEvtApiError = null;
+ private Throwable kernel32Error = null;
+
+ private WEvtApi.EVT_SUBSCRIBE_CALLBACK evtSubscribeCallback;
+ private WinNT.HANDLE subscriptionHandle;
+
+ private WEvtApi loadWEvtApi() {
+ try {
+ return WEvtApi.INSTANCE;
+ } catch (Throwable e) {
+ wEvtApiError = e;
+ return null;
+ }
+ }
+
+ private Kernel32 loadKernel32() {
+ try {
+ return Kernel32.INSTANCE;
+ } catch (Throwable e) {
+ kernel32Error = e;
+ return null;
+ }
+ }
+
+ /**
+ * Framework constructor
+ */
+ public EvtSubscribe() {
+ this(null, null);
+ }
+
+ /**
+ * Constructor that allows injection of JNA interfaces
+ *
+ * @param wEvtApi event api interface
+ * @param kernel32 kernel interface
+ */
+ public EvtSubscribe(WEvtApi wEvtApi, Kernel32 kernel32) {
+ this.wEvtApi = wEvtApi == null ? loadWEvtApi() : wEvtApi;
+ this.kernel32 = kernel32 == null ? loadKernel32() : kernel32;
+ this.sessionFactoryReference = new AtomicReference<>();
+ this.renderedXMLs = new LinkedList<>();
+ }
+
+ /**
+ * Register subscriber via native call
+ *
+ * @param context the process context
+ */
+ @OnScheduled
+ public void subscribeToEvents(ProcessContext context) {
+ int maxEventQueueSize =
context.getProperty(MAX_EVENT_QUEUE_SIZE).asInteger();
+ evtSubscribeCallback = new
EventSubscribeXmlRenderingCallback(getLogger(), s -> {
+ ProcessSessionFactory processSessionFactory =
sessionFactoryReference.get();
+ if (processSessionFactory == null) {
+ addRenderedXml(s, maxEventQueueSize);
+ } else {
+ ProcessSession session =
processSessionFactory.createSession();
+ createAndTransferEventFlowFile(session, s);
+ session.commit();
--- End diff --
In general you should refrain from transferring FlowFiles outside of an
onTrigger. This processor is following the ConsumeX paradigm. Where there is a
resource pushing data to the processor which is a bit tricky when a processor
should only emit FlowFiles when triggered.
For a good reference for how to address concerns like to store the data,
how much to store, when to transferred the data and what to do when the
processor is stopped (I transfer the lingering data to avoid data loss) check
out my ConsumeMqtt processor[1]. It is the same general idea but instead of
getting Windows events pushed to it, it gets MQTT messages pushed to it.
[1]
https://github.com/apache/nifi/blob/master/nifi-nar-bundles/nifi-mqtt-bundle/nifi-mqtt-processors/src/main/java/org/apache/nifi/processors/mqtt/ConsumeMQTT.java
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at infrastruct...@apache.org or file a JIRA ticket
with INFRA.
---
