how reading nutch generated content data on the segment folder using java - nutch

Question

I am trying to read the content data inside the segment folder. I think the content data file is written in a custom format
I experimented with nutch's Content class, but it does not recognize the format.

Answer 1

import java.io.IOException;
import org.apache.commons.cli.Options;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.SequenceFile;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.util.GenericOptionsParser;
import org.apache.nutch.protocol.Content;
import org.apache.nutch.util.NutchConfiguration;
public class ContentReader {
public static void main(String[] args) throws IOException {
// Setup the parser
Configuration conf = NutchConfiguration.create();
Options opts = new Options();
GenericOptionsParser parser = new GenericOptionsParser(conf, opts, args);
String[] remainingArgs = parser.getRemainingArgs();
FileSystem fs = FileSystem.get(conf);
String segment = remainingArgs[0];
Path file = new Path(segment, Content.DIR_NAME + "/part-00000/data");
SequenceFile.Reader reader = new SequenceFile.Reader(fs, file, conf);
Text key = new Text();
Content content = new Content();
// Loop through sequence files
while (reader.next(key, content)) {
try {
System.out.write(content.getContent(), 0,
content.getContent().length);
} catch (Exception e) {
}
}
}
}

Answer 2

org.apache.nutch.segment.SegmentReader
has a map reduce implementation that reads content data in the segment directory.

Answer 3

spark/scala code to read data from the segments content folder.
How I read from the content folder in my project.
I have created a case class page which holds data read from the content folder
case class Page(var url: String, var title: String = null
,var contentType: String = null, var rawHtml: String = null,var language: String = null
,var metadata: Map[String,String])
Code to read from content folder
import org.apache.commons.lang3.StringUtils
import org.apache.hadoop.io.{Text, Writable}
import org.apache.nutch.crawl.{CrawlDatum, Inlinks}
import org.apache.nutch.parse.ParseText
import org.apache.nutch.protocol.Content
val contentDF = spark.sparkContext.sequenceFile(path.contentLocation, classOf[Text], classOf[Writable])
.map { case (x, y) => (x.toString, extract(y.asInstanceOf[Content])) }
/** converts Content object to Page **/
def extract(content: Content): Page = {
try {
val parsed = Page(content.getUrl)
var charset: String = getCharsetFromContentType(content.getContentType)
if (StringUtils.isBlank(charset)) {
charset = "UTF-8"
}
parsed.rawHtml = Try(new String(content.getContent, charset)).getOrElse(new String(content.getContent, "UTF-8"))
parsed.contentType = Try(content.getMetadata.get("Content-Type")).getOrElse("text/html")
// parsed.isHomePage = Boolean.valueOf(content.getMetadata.get("isHomePage"))
parsed.metadata = content.getMetadata.names().map(name => (name,content.getMetadata.get(name))).toMap
Try {
if (StringUtils.isNotBlank(content.getMetadata.get("Content-Language")))
parsed.language = content.getMetadata.get("Content-Language")
else if (StringUtils.isNotBlank(content.getMetadata.get("language")))
parsed.language = content.getMetadata.get("language")
else parsed.language = content.getMetadata.get("lang")
}
parsed
} catch {
case e: Exception =>
LOG.error("ERROR while extracting data from Content ", e)
null
}
}
/**Get Html ContentType **/
def getCharsetFromContentType(contentType: String): String = {
var result: String = "UTF-8"
Try {
if (StringUtils.isNotBlank(contentType)) {
val m = charsetPattern.matcher(contentType)
result = if (m.find) m.group(1).trim.toUpperCase else "UTF-8"
}
}
result
}