is there any way to fix solr index - solr

Question

I am running a program that crawls the web and saves data into a solr index. for mysterious reasons, the solr server crashed. And now I end up with a corrupted index that has no segment files and hence risking losing all my data collected for 5 days....
The error message reads as below when you try to search on this index. the index folder definitely has data, as it has 182 files and 2GB in size.
I have tried to use CheckIndex but get the same error about no segment files...
java.util.concurrent.ExecutionException: org.apache.solr.common.SolrException: Unable to create core [chase]
at java.util.concurrent.FutureTask.report(FutureTask.java:122)
at java.util.concurrent.FutureTask.get(FutureTask.java:192)
at org.apache.solr.core.CoreContainer.lambda$load$6(CoreContainer.java:586)
at com.codahale.metrics.InstrumentedExecutorService$InstrumentedRunnable.run(InstrumentedExecutorService.java:176)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at org.apache.solr.common.util.ExecutorUtil$MDCAwareThreadPoolExecutor.lambda$execute$0(ExecutorUtil.java:229)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:748)
Caused by: org.apache.solr.common.SolrException: Unable to create core [chase]
at org.apache.solr.core.CoreContainer.create(CoreContainer.java:935)
at org.apache.solr.core.CoreContainer.lambda$load$5(CoreContainer.java:558)
at com.codahale.metrics.InstrumentedExecutorService$InstrumentedCallable.call(InstrumentedExecutorService.java:197)
... 5 more
Caused by: org.apache.solr.common.SolrException: Error opening new searcher
at org.apache.solr.core.SolrCore.<init>(SolrCore.java:977)
at org.apache.solr.core.SolrCore.<init>(SolrCore.java:830)
at org.apache.solr.core.CoreContainer.create(CoreContainer.java:920)
... 7 more
Caused by: org.apache.solr.common.SolrException: Error opening new searcher
at org.apache.solr.core.SolrCore.openNewSearcher(SolrCore.java:2069)
at org.apache.solr.core.SolrCore.getSearcher(SolrCore.java:2189)
at org.apache.solr.core.SolrCore.initSearcher(SolrCore.java:1071)
at org.apache.solr.core.SolrCore.<init>(SolrCore.java:949)
... 9 more
Caused by: org.apache.lucene.index.IndexNotFoundException: no segments* file found in LockValidatingDirectoryWrapper(NRTCachingDirectory(MMapDirectory#/home/zqz/Work/chase/aws/data/solr/chase/data/index lockFactory=org.apache.lucene.store.NativeFSLockFactory#51b2fc7e; maxCacheMB=48.0 maxMergeSizeMB=4.0)): files: [_fh2.fdt, _fh2.fdx, _fh2.fnm, _fh2.nvd, _fh2.nvm, _fh2.si, _fh2_Lucene50_0.doc, _fh2_Lucene50_0.pos, _fh2_Lucene50_0.tim, _fh2_Lucene50_0.tip, write.lock]
at org.apache.lucene.index.IndexWriter.<init>(IndexWriter.java:925)
at org.apache.solr.update.SolrIndexWriter.<init>(SolrIndexWriter.java:118)
at org.apache.solr.update.SolrIndexWriter.create(SolrIndexWriter.java:93)
at org.apache.solr.update.DefaultSolrCoreState.createMainIndexWriter(DefaultSolrCoreState.java:248)
at org.apache.solr.update.DefaultSolrCoreState.getIndexWriter(DefaultSolrCoreState.java:122)
at org.apache.solr.core.SolrCore.openNewSearcher(SolrCore.java:2030)
... 12 more
2017-06-20 14:38:52.428 INFO (qtp475266352-16) [ ] o.a.s.c.TransientSolrCoreCacheDefault Allocating transient cache for 2147483647 transient cores
2017-06-20 14:38:52.894 INFO (qtp475266352-13) [ ] o.a.s.s.HttpSolrCall [admin] webapp=null path=/admin/cores params={indexInfo=false&wt=json&_=1497969532681} status=0 QTime=11
2017-06-20 14:38:52.962 INFO (qtp475266352-20) [ ] o.a.s.s.HttpSolrCall [admin] webapp=null path=/admin/info/system params={wt=json&_=1497969532684} status=0 QTime=76

Answer 1

The error you mentioned is caused by the missing file :
segments* e.g. segments_3 ...
in the index files :
files: [_fh2.fdt, _fh2.fdx, _fh2.fnm, _fh2.nvd, _fh2.nvm, _fh2.si, _fh2_Lucene50_0.doc, _fh2_Lucene50_0.pos, _fh2_Lucene50_0.tim, _fh2_Lucene50_0.tip, write.lock]
That file specifies the last commit point and the last generation of segments to take into account and apparently it is missing.
Check if that file is there and is readable.
If it is not ( because for example the index writer was not closed properly due to the mulfuction, do not despair.
Chances are there that the transaction log contains still the documents you indexed, so you could just replay it and get the documents back ( clean the index dir, make solr starting and it should take care).
Solr allows also a backup functionality, so for the future you may want to configure it.