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From olegz <...@git.apache.org>
Subject [GitHub] nifi pull request #525: NIFI-1976 - Windows Event Log native processor
Date Wed, 29 Jun 2016 17:19:37 GMT
Github user olegz commented on a diff in the pull request:

    https://github.com/apache/nifi/pull/525#discussion_r68989065
  
    --- 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);
    +            } catch (InterruptedException e) {
    +                throw new IllegalStateException("Got interrupted while waiting to add
to queue.", e);
    +            }
    +        }, context.getProperty(MAX_BUFFER_SIZE).asInteger(), wEvtApi, kernel32, errorLookup);
    +
    +        subscriptionHandle = wEvtApi.EvtSubscribe(null, null, channel, query, null, null,
    +                evtSubscribeCallback, WEvtApi.EvtSubscribeFlags.SUBSCRIBE_TO_FUTURE);
    +        if (subscriptionHandle == null || subscriptionHandle.getPointer() == null) {
    +            throw new Exception("Unable to subscribe with provided parameters, received
the following error code: "
    +                    + errorLookup.getLastError());
    +        }
    +    }
    +
    +    /**
    +     * Cleanup
    +     */
    +    @OnStopped
    +    public void stop() {
    +        wEvtApi.EvtClose(subscriptionHandle);
    +        subscriptionHandle = null;
    +        evtSubscribeCallback = null;
    +        if (!renderedXMLs.isEmpty()) {
    +            if (sessionFactory != null) {
    +                getLogger().info("Finishing processing leftover events");
    +                ProcessSession session = sessionFactory.createSession();
    +                processQueue(session);
    +            } else {
    +                throw new ProcessException("Stopping the processor but there is no ProcessSessionFactory
stored and there are messages in the internal queue. Removing the processor now will " +
    +                        "clear the queue but will result in DATA LOSS. This is normally
due to starting the processor, receiving events and stopping before the onTrigger happens.
The messages " +
    +                        "in the internal queue cannot finish processing until until the
processor is triggered to run.");
    +            }
    +        }
    +        sessionFactory = null;
    +        provenanceUri = null;
    +        renderedXMLs = null;
    +    }
    +
    +    @Override
    +    public void onTrigger(ProcessContext context, ProcessSessionFactory sessionFactory)
throws ProcessException {
    +        this.sessionFactory = sessionFactory;
    --- End diff --
    
    Well, in this particular case it is safe since you are simply assigning reference. That
said and given that the actual value is passed within the method call one must assume (regardless
of the actual case) that the passed value may be different. This means that this value is
only valid for the duration of the callback. I haven't reviewed the code thoroughly, but I
don't see the reason why it has to be assigned to an instance variable. Instead consider a
_private_ method where you wold pass this value in the context of _onTrigger(..)_.


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