flume学习（八）：自定义拦截器

还是针对学习七中的那个需求，我们现在换一种实现方式，采用拦截器来实现。

先回想一下，spooldir source可以将文件名作为header中的key:basename写入到event的header当中去。试想一下，如果有一个拦截器可以拦截这个event,然后抽取header中这个key的值，将其拆分成3段，每一段都放入到header中，这样就可以实现那个需求了。

遗憾的是，flume没有提供可以拦截header的拦截器。不过有一个抽取body内容的拦截器：RegexExtractorInterceptor，看起来也很强大，以下是一个官方文档的示例：

If the Flume event body contained 1:2:3.4foobar5 and the following configuration was used

a1.sources.r1.interceptors.i1.regex = (\\d):(\\d):(\\d)
a1.sources.r1.interceptors.i1.serializers = s1 s2 s3
a1.sources.r1.interceptors.i1.serializers.s1.name = one
a1.sources.r1.interceptors.i1.serializers.s2.name = two
a1.sources.r1.interceptors.i1.serializers.s3.name = three
The extracted event will contain the same body but the following headers will have been added one=>1, two=>2, three=>3

大概意思就是，通过这样的配置，event body中如果有1:2:3.4foobar5 这样的内容，这会通过正则的规则抽取具体部分的内容，然后设置到header当中去。

于是决定打这个拦截器的主义，觉得只要把代码稍微改改，从拦截body改为拦截header中的具体key，就OK了。翻开源码，哎呀，很工整，改起来没难度，以下是我新增的一个拦截器：RegexExtractorExtInterceptor：

[java] view plaincopy

package com.besttone.flume;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.commons.lang.StringUtils;
import org.apache.flume.Context;
import org.apache.flume.Event;
import org.apache.flume.interceptor.Interceptor;
import org.apache.flume.interceptor.RegexExtractorInterceptorPassThroughSerializer;
import org.apache.flume.interceptor.RegexExtractorInterceptorSerializer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.google.common.base.Charsets;
import com.google.common.base.Preconditions;
import com.google.common.base.Throwables;
import com.google.common.collect.Lists;
/**
* Interceptor that extracts matches using a specified regular expression and
* appends the matches to the event headers using the specified serializers
* Note that all regular expression matching occurs through Java's built in
* java.util.regex package. Properties:
*
* regex: The regex to use
*
* serializers: Specifies the group the serializer will be applied to, and the
* name of the header that will be added. If no serializer is specified for a
* group the default {@link RegexExtractorInterceptorPassThroughSerializer} will
* be used
*
* Sample config:
*
* agent.sources.r1.channels = c1
*
* agent.sources.r1.type = SEQ
*
* agent.sources.r1.interceptors = i1
*
* agent.sources.r1.interceptors.i1.type = REGEX_EXTRACTOR
*
* agent.sources.r1.interceptors.i1.regex = (WARNING)|(ERROR)|(FATAL)
*
* agent.sources.r1.interceptors.i1.serializers = s1 s2
* agent.sources.r1.interceptors.i1.serializers.s1.type =
* com.blah.SomeSerializer agent.sources.r1.interceptors.i1.serializers.s1.name
* = warning agent.sources.r1.interceptors.i1.serializers.s2.type =
* org.apache.flume.interceptor.RegexExtractorInterceptorTimestampSerializer
* agent.sources.r1.interceptors.i1.serializers.s2.name = error
* agent.sources.r1.interceptors.i1.serializers.s2.dateFormat = yyyy-MM-dd
* </code>
*
*
* <pre>
* Example 1:
*
* EventBody: 1:2:3.4foobar5 Configuration:
* agent.sources.r1.interceptors.i1.regex = (\\d):(\\d):(\\d)
*
* agent.sources.r1.interceptors.i1.serializers = s1 s2 s3
* agent.sources.r1.interceptors.i1.serializers.s1.name = one
* agent.sources.r1.interceptors.i1.serializers.s2.name = two
* agent.sources.r1.interceptors.i1.serializers.s3.name = three
*
* results in an event with the the following
*
* body: 1:2:3.4foobar5 headers: one=>1, two=>2, three=3
*
* Example 2:
*
* EventBody: 1:2:3.4foobar5
*
* Configuration: agent.sources.r1.interceptors.i1.regex = (\\d):(\\d):(\\d)
*
* agent.sources.r1.interceptors.i1.serializers = s1 s2
* agent.sources.r1.interceptors.i1.serializers.s1.name = one
* agent.sources.r1.interceptors.i1.serializers.s2.name = two
*
*
* results in an event with the the following
*
* body: 1:2:3.4foobar5 headers: one=>1, two=>2
* </pre>
*/
public class RegexExtractorExtInterceptor implements Interceptor {
static final String REGEX = "regex";
static final String SERIALIZERS = "serializers";
// 增加代码开始
static final String EXTRACTOR_HEADER = "extractorHeader";
static final boolean DEFAULT_EXTRACTOR_HEADER = false;
static final String EXTRACTOR_HEADER_KEY = "extractorHeaderKey";
// 增加代码结束
private static final Logger logger = LoggerFactory
.getLogger(RegexExtractorExtInterceptor.class);
private final Pattern regex;
private final List<NameAndSerializer> serializers;
// 增加代码开始
private final boolean extractorHeader;
private final String extractorHeaderKey;
// 增加代码结束
private RegexExtractorExtInterceptor(Pattern regex,
List<NameAndSerializer> serializers, boolean extractorHeader,
String extractorHeaderKey) {
this.regex = regex;
this.serializers = serializers;
this.extractorHeader = extractorHeader;
this.extractorHeaderKey = extractorHeaderKey;
}
@Override
public void initialize() {
// NO-OP...
}
@Override
public void close() {
// NO-OP...
}
@Override
public Event intercept(Event event) {
String tmpStr;
if(extractorHeader)
{
tmpStr = event.getHeaders().get(extractorHeaderKey);
}
else
{
tmpStr=new String(event.getBody(),
Charsets.UTF_8);
}
Matcher matcher = regex.matcher(tmpStr);
Map<String, String> headers = event.getHeaders();
if (matcher.find()) {
for (int group = 0, count = matcher.groupCount(); group < count; group++) {
int groupIndex = group + 1;
if (groupIndex > serializers.size()) {
if (logger.isDebugEnabled()) {
logger.debug(
"Skipping group {} to {} due to missing serializer",
group, count);
}
break;
}
NameAndSerializer serializer = serializers.get(group);
if (logger.isDebugEnabled()) {
logger.debug("Serializing {} using {}",
serializer.headerName, serializer.serializer);
}
headers.put(serializer.headerName, serializer.serializer
.serialize(matcher.group(groupIndex)));
}
}
return event;
}
@Override
public List<Event> intercept(List<Event> events) {
List<Event> intercepted = Lists.newArrayListWithCapacity(events.size());
for (Event event : events) {
Event interceptedEvent = intercept(event);
if (interceptedEvent != null) {
intercepted.add(interceptedEvent);
}
}
return intercepted;
}
public static class Builder implements Interceptor.Builder {
private Pattern regex;
private List<NameAndSerializer> serializerList;
// 增加代码开始
private boolean extractorHeader;
private String extractorHeaderKey;
// 增加代码结束
private final RegexExtractorInterceptorSerializer defaultSerializer = new RegexExtractorInterceptorPassThroughSerializer();
@Override
public void configure(Context context) {
String regexString = context.getString(REGEX);
Preconditions.checkArgument(!StringUtils.isEmpty(regexString),
"Must supply a valid regex string");
regex = Pattern.compile(regexString);
regex.pattern();
regex.matcher("").groupCount();
configureSerializers(context);
// 增加代码开始
extractorHeader = context.getBoolean(EXTRACTOR_HEADER,
DEFAULT_EXTRACTOR_HEADER);
if (extractorHeader) {
extractorHeaderKey = context.getString(EXTRACTOR_HEADER_KEY);
Preconditions.checkArgument(
!StringUtils.isEmpty(extractorHeaderKey),
"必须指定要抽取内容的header key");
}
// 增加代码结束
}
private void configureSerializers(Context context) {
String serializerListStr = context.getString(SERIALIZERS);
Preconditions.checkArgument(
!StringUtils.isEmpty(serializerListStr),
"Must supply at least one name and serializer");
String[] serializerNames = serializerListStr.split("\\s+");
Context serializerContexts = new Context(
context.getSubProperties(SERIALIZERS + "."));
serializerList = Lists
.newArrayListWithCapacity(serializerNames.length);
for (String serializerName : serializerNames) {
Context serializerContext = new Context(
serializerContexts.getSubProperties(serializerName
+ "."));
String type = serializerContext.getString("type", "DEFAULT");
String name = serializerContext.getString("name");
Preconditions.checkArgument(!StringUtils.isEmpty(name),
"Supplied name cannot be empty.");
if ("DEFAULT".equals(type)) {
serializerList.add(new NameAndSerializer(name,
defaultSerializer));
} else {
serializerList.add(new NameAndSerializer(name,
getCustomSerializer(type, serializerContext)));
}
}
}
private RegexExtractorInterceptorSerializer getCustomSerializer(
String clazzName, Context context) {
try {
RegexExtractorInterceptorSerializer serializer = (RegexExtractorInterceptorSerializer) Class
.forName(clazzName).newInstance();
serializer.configure(context);
return serializer;
} catch (Exception e) {
logger.error("Could not instantiate event serializer.", e);
Throwables.propagate(e);
}
return defaultSerializer;
}
@Override
public Interceptor build() {
Preconditions.checkArgument(regex != null,
"Regex pattern was misconfigured");
Preconditions.checkArgument(serializerList.size() > 0,
"Must supply a valid group match id list");
return new RegexExtractorExtInterceptor(regex, serializerList,
extractorHeader, extractorHeaderKey);
}
}
static class NameAndSerializer {
private final String headerName;
private final RegexExtractorInterceptorSerializer serializer;
public NameAndSerializer(String headerName,
RegexExtractorInterceptorSerializer serializer) {
this.headerName = headerName;
this.serializer = serializer;
}
}
}

简单说明一下改动的内容：

增加了两个配置参数：

extractorHeader 是否抽取的是header部分，默认为false,即和原始的拦截器功能一致，抽取的是event body的内容

extractorHeaderKey 抽取的header的指定的key的内容，当extractorHeader为true时，必须指定该参数。

按照第七讲的方法，我们将该类打成jar包，作为flume的插件放到了/var/lib/flume-ng/plugins.d/RegexExtractorExtInterceptor/lib目录下，重新启动flume，将该拦截器加载到classpath中。

最终的flume.conf如下：

[plain] view plaincopy

tier1.sources=source1
tier1.channels=channel1
tier1.sinks=sink1
tier1.sources.source1.type=spooldir
tier1.sources.source1.spoolDir=/opt/logs
tier1.sources.source1.fileHeader=true
tier1.sources.source1.basenameHeader=true
tier1.sources.source1.interceptors=i1
tier1.sources.source1.interceptors.i1.type=com.besttone.flume.RegexExtractorExtInterceptor$Builder
tier1.sources.source1.interceptors.i1.regex=(.*)\\.(.*)\\.(.*)
tier1.sources.source1.interceptors.i1.extractorHeader=true
tier1.sources.source1.interceptors.i1.extractorHeaderKey=basename
tier1.sources.source1.interceptors.i1.serializers=s1 s2 s3
tier1.sources.source1.interceptors.i1.serializers.s1.name=one
tier1.sources.source1.interceptors.i1.serializers.s2.name=two
tier1.sources.source1.interceptors.i1.serializers.s3.name=three
tier1.sources.source1.channels=channel1
tier1.sinks.sink1.type=hdfs
tier1.sinks.sink1.channel=channel1
tier1.sinks.sink1.hdfs.path=hdfs://master68:8020/flume/events/%{one}/%{three}
tier1.sinks.sink1.hdfs.round=true
tier1.sinks.sink1.hdfs.roundValue=10
tier1.sinks.sink1.hdfs.roundUnit=minute
tier1.sinks.sink1.hdfs.fileType=DataStream
tier1.sinks.sink1.hdfs.writeFormat=Text
tier1.sinks.sink1.hdfs.rollInterval=0
tier1.sinks.sink1.hdfs.rollSize=10240
tier1.sinks.sink1.hdfs.rollCount=0
tier1.sinks.sink1.hdfs.idleTimeout=60
tier1.channels.channel1.type=memory
tier1.channels.channel1.capacity=10000
tier1.channels.channel1.transactionCapacity=1000
tier1.channels.channel1.keep-alive=30

我把source type改回了内置的spooldir，而不是上一讲自定义的source,然后添加了一个拦截器i1,type是自定义的拦截器：com.besttone.flume.RegexExtractorExtInterceptor$Builder,正则表达式按“.”分隔抽取三部分，分别放到header中的key:one,two,three当中去，即a.log.2014-07-31,通过拦截器后，在header当中就会增加三个key: one=a,two=log,three=2014-07-31。这时候我们在tier1.sinks.sink1.hdfs.path=hdfs://master68:8020/flume/events/%{one}/%{three}。

就实现了和前面第七讲一模一样的需求。

也可以看到，自定义拦截器的改动成本非常小，比自定义source小多了，我们这就增加了一个类，就实现了该功能。

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