Hello, I am writing an application that performs web site crawling using Nutch REST services. The application:
1. Injects seed URLs once 2. Repeats GENERATE/FETCH/PARSE/UPDATEDB sequence requested number of times to emulated continuous crawling (each step in sequence is executed upon successful competition of the previous step then sequence repeated again) The application is also capable of running multiple crawls with different crawl IDs at the same time. That seems to be putting stress on Nutch and it starts to fail with the following error: "Cannot run job worker!". The parallel crawling seems to be starting normally with corresponding Nutch jobs finishing as expected but eventually they start to break. Here are some details on crawling (work fine for non-parallel crawls): - Seed URL: http://www.cnn.com - Regex URL filters: "-^.{1000,}$" and "+." (1. Exclude very long URLs; 2. Include the rest) - fetcher.threads.fetch in nutch-site.xml: 2 (smaller number seems to reproduce the problem faster, 100 as a value takes longer) - Number of parallel crawls: 7 Here is an example of failed job status (in this case GENERATE step failed but saw PARSE failing with the same error in other test executions): { "id" : "parallel_0-65ff2f1b-382e-4eb2-a813-a0370b84d5b6-GENERATE-1961495833", "type" : "GENERATE", "confId" : "65ff2f1b-382e-4eb2-a813-a0370b84d5b6", "args" : { "topN" : "100" }, "result" : null, "state" : "FAILED", "msg" : "ERROR: java.lang.RuntimeException: job failed: name=[parallel_0]generate: 1498059912-1448058551, jobid=job_local1142434549_0036", "crawlId" : "parallel_0" } Lines from hadoop.log: 2017-06-21 11:45:13,021 WARN mapred.LocalJobRunner - job_local1142434549_0036 java.lang.Exception: java.lang.RuntimeException: java.io.EOFException at org.apache.hadoop.mapred.LocalJobRunner$Job.runTasks(LocalJobRunner.java:462) at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:529) Caused by: java.lang.RuntimeException: java.io.EOFException at org.apache.hadoop.io.WritableComparator.compare(WritableComparator.java:164) at org.apache.hadoop.mapreduce.task.ReduceContextImpl.nextKeyValue(ReduceContextImpl.java:158) at org.apache.hadoop.mapreduce.task.ReduceContextImpl.nextKey(ReduceContextImpl.java:121) at org.apache.hadoop.mapreduce.lib.reduce.WrappedReducer$Context.nextKey(WrappedReducer.java:302) at org.apache.hadoop.mapreduce.Reducer.run(Reducer.java:170) at org.apache.hadoop.mapred.ReduceTask.runNewReducer(ReduceTask.java:627) at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:389) at org.apache.hadoop.mapred.LocalJobRunner$Job$ReduceTaskRunnable.run(LocalJobRunner.java:319) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745) Caused by: java.io.EOFException at java.io.DataInputStream.readFully(DataInputStream.java:197) at org.apache.hadoop.io.Text.readString(Text.java:466) at org.apache.hadoop.io.Text.readString(Text.java:457) at org.apache.nutch.crawl.GeneratorJob$SelectorEntry.readFields(GeneratorJob.java:92) at org.apache.hadoop.io.WritableComparator.compare(WritableComparator.java:158) ... 12 more 2017-06-21 11:45:13,058 WARN mapred.LocalJobRunner - job_local1976432650_0038 java.lang.Exception: java.lang.RuntimeException: java.io.EOFException at org.apache.hadoop.mapred.LocalJobRunner$Job.runTasks(LocalJobRunner.java:462) at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:522) Caused by: java.lang.RuntimeException: java.io.EOFException at org.apache.hadoop.io.WritableComparator.compare(WritableComparator.java:164) at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.compare(MapTask.java:1245) at org.apache.hadoop.util.QuickSort.sortInternal(QuickSort.java:99) at org.apache.hadoop.util.QuickSort.sortInternal(QuickSort.java:126) at org.apache.hadoop.util.QuickSort.sort(QuickSort.java:63) at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.sortAndSpill(MapTask.java:1575) at org.apache.hadoop.mapred.MapTask$MapOutputBuffer.flush(MapTask.java:1462) at org.apache.hadoop.mapred.MapTask$NewOutputCollector.close(MapTask.java:700) at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:770) at org.apache.hadoop.mapred.MapTask.run(MapTask.java:340) at org.apache.hadoop.mapred.LocalJobRunner$Job$MapTaskRunnable.run(LocalJobRunner.java:243) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745) Caused by: java.io.EOFException at java.io.DataInputStream.readByte(DataInputStream.java:267) at org.apache.hadoop.io.WritableUtils.readVLong(WritableUtils.java:308) at org.apache.hadoop.io.WritableUtils.readVIntInRange(WritableUtils.java:348) at org.apache.hadoop.io.Text.readString(Text.java:464) at org.apache.hadoop.io.Text.readString(Text.java:457) at org.apache.nutch.crawl.GeneratorJob$SelectorEntry.readFields(GeneratorJob.java:92) at org.apache.hadoop.io.WritableComparator.compare(WritableComparator.java:158) ... 15 more ... 2017-06-21 11:45:13,372 ERROR impl.JobWorker - Cannot run job worker! java.lang.RuntimeException: job failed: name=[parallel_0]generate: 1498059912-1448058551, jobid=job_local1142434549_0036 at org.apache.nutch.util.NutchJob.waitForCompletion(NutchJob.java:120) at org.apache.nutch.crawl.GeneratorJob.run(GeneratorJob.java:227) at org.apache.nutch.api.impl.JobWorker.run(JobWorker.java:64) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745) Regards, Vyacheslav Pascarel
