[NUTCH-2474] CrawlDbReader -stats fails with ClassCastException

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 1.14
• Fix Version/s: 1.14
• Component/s: crawldb

Environment

Java 8, distributed mode: Hadoop CDH 5.13.0

• Assignee: Sebastian Nagel
• Reporter: Sebastian Nagel
• Created: 08/Dec/17 09:17
• Updated: 13/Mar/24 14:51
• Resolved: 14/Dec/17 15:13

Description

In distributed mode CrawlDbReader / readdb -stats fails with a ClassCastException in the combiner:

17/12/08 04:57:13 INFO mapreduce.Job: Task Id : attempt_1512553291624_0022_m_000039_0, Status : FAILED
Error: java.lang.ClassCastException: org.apache.hadoop.io.FloatWritable cannot be cast to org.apache.hadoop.io.LongWritable
        at org.apache.nutch.crawl.CrawlDbReader$CrawlDbStatCombiner.reduce(CrawlDbReader.java:296)
        at org.apache.nutch.crawl.CrawlDbReader$CrawlDbStatCombiner.reduce(CrawlDbReader.java:222)
        at org.apache.hadoop.mapred.Task$OldCombinerRunner.combine(Task.java:1639)
        at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.mergeParts(MapTask.java:1946)
        at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.flush(MapTask.java:1514)
        at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:466)
        at org.apache.hadoop.mapred.MapTask.run(MapTask.java:343)

FloatWritables are used since NUTCH-2470, so that's when this bug was introduced.

Issue Links

• incorporates: NUTCH-2297 CrawlDbReader -stats wrong values for earliest fetch time and shortest interval
• supercedes: NUTCH-2297 CrawlDbReader -stats wrong values for earliest fetch time and shortest interval
• links to: GitHub Pull Request #255