Github user brosander commented on a diff in the pull request:
https://github.com/apache/nifi/pull/525#discussion_r68759636
--- Diff:
nifi-nar-bundles/nifi-windows-event-log-bundle/nifi-windows-event-log-processors/src/main/java/org/apache/nifi/processors/windows/event/log/ConsumeWindowsEventLog.java
---
@@ -0,0 +1,282 @@
+/*
+ * 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.sun.jna.platform.win32.Kernel32;
+import com.sun.jna.platform.win32.Kernel32Util;
+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.TriggerSerially;
+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.ErrorLookup;
+import
org.apache.nifi.processors.windows.event.log.jna.EventSubscribeXmlRenderingCallback;
+import org.apache.nifi.processors.windows.event.log.jna.WEvtApi;
+
+import java.net.URI;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.LinkedBlockingQueue;
+
+
+@InputRequirement(InputRequirement.Requirement.INPUT_FORBIDDEN)
+@Tags({"ingest", "event", "windows"})
+@TriggerSerially
+@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 ConsumeWindowsEventLog 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.")
+ .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 consumed events.")
+ .build();
+
+ public static final Set<Relationship> RELATIONSHIPS =
Collections.unmodifiableSet(new HashSet<>(Arrays.asList(REL_SUCCESS)));
+ public static final String APPLICATION_XML = "application/xml";
+ private final WEvtApi wEvtApi;
+ private final Kernel32 kernel32;
+ private final ErrorLookup errorLookup;
+ private final String name;
+
+ private Throwable wEvtApiError = null;
+ private Throwable kernel32Error = null;
+
+ private BlockingQueue<String> renderedXMLs;
+ private WEvtApi.EVT_SUBSCRIBE_CALLBACK evtSubscribeCallback;
+ private WinNT.HANDLE subscriptionHandle;
+ private ProcessSessionFactory sessionFactory;
+ private String provenanceUri;
+
+ /**
+ * Framework constructor
+ */
+ public ConsumeWindowsEventLog() {
+ this(null, null);
+ }
+
+ /**
+ * Constructor that allows injection of JNA interfaces
+ *
+ * @param wEvtApi event api interface
+ * @param kernel32 kernel interface
+ */
+ public ConsumeWindowsEventLog(WEvtApi wEvtApi, Kernel32 kernel32) {
+ this.wEvtApi = wEvtApi == null ? loadWEvtApi() : wEvtApi;
+ this.kernel32 = kernel32 == null ? loadKernel32() : kernel32;
+ this.errorLookup = new ErrorLookup(this.kernel32);
+ if (kernel32 != null) {
+ name = Kernel32Util.getComputerName();
+ } else {
+ // Won't be able to use the processor anyway because native
libraries didn't load
+ name = null;
+ }
+ }
+
+ 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;
+ }
+ }
+
+ /**
+ * Register subscriber via native call
+ *
+ * @param context the process context
+ */
+ @OnScheduled
+ public void onScheduled(ProcessContext context) throws Exception {
+ String channel = context.getProperty(CHANNEL).getValue();
+ String query = context.getProperty(QUERY).getValue();
+
+ renderedXMLs = new
LinkedBlockingQueue<>(context.getProperty(MAX_EVENT_QUEUE_SIZE).asInteger());
+ provenanceUri = new URI("winlog", name, "/" + channel, query,
null).toASCIIString();
+
+ evtSubscribeCallback = new
EventSubscribeXmlRenderingCallback(getLogger(), s -> {
+ try {
+ renderedXMLs.put(s);
--- End diff --
The documentation states that while the callback is running, it will block
further events, implying that it will not spawn extra threads for each
callback. [1][2] I took this to mean that it would make a best-effort attempt
not to miss events on a single thread. We could set the EvtSubscribeStrict
flag and log ERROR_EVT_QUERY_RESULT_STALE callbacks to let the user know it's
happening.
I'd rather not add another place where we could possibly drop events if
possible, since it seems like the api itself already has a release valve.
[1]
https://msdn.microsoft.com/en-us/library/windows/desktop/aa385577(v=vs.85).aspx
[2]
http://stackoverflow.com/questions/6901540/evtsubscribe-and-threading#answer-6903656
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