Caused by: org.apache.solr.common.SolrException: Index locked for write for core

We are using solr4.3 with master/slave setup, today I got the following error and solr stopped responding. What could be causing this,

 Caused by: org.apache.solr.common.SolrException: Index locked for write for core XXX
    at org.apache.solr.core.SolrCore.<init>(SolrCore.java:821)
    at org.apache.solr.core.SolrCore.<init>(SolrCore.java:618)
    at org.apache.solr.core.CoreContainer.createFromLocal(CoreContainer.java:949)
    at org.apache.solr.core.CoreContainer.create(CoreContainer.java:984)
    at org.apache.solr.core.CoreContainer$2.call(CoreContainer.java:597)
    at org.apache.solr.core.CoreContainer$2.call(CoreContainer.java:592)
    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
    at java.util.concurrent.FutureTask.run(FutureTask.java:138)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:439)
    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
    at java.util.concurrent.FutureTask.run(FutureTask.java:138)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
    ... 1 more
Caused by: org.apache.lucene.store.LockObtainFailedException: Index locked for write for core XX        at org.apache.solr.core.SolrCore.initIndex(SolrCore.java:484)
    at org.apache.solr.core.SolrCore.<init>(SolrCore.java:745)
    ... 13 more

It seems the index has been locked during indexing.
Usually there would be a write.lock file within the index which needs to be removed to get it back.
The conditions can occur if the indexing breaks in between or other issues which may cause to lock file to be still in the index.

Check Forum

The write lock is due to the fact that an IndexWriter is always open in Solr even on the slaves.

Check for the Index Lock options which can handle the condition within configuration.

[An archived copy of the original link: https://web.archive.org/web/http://docs.lucidworks.com/display/solr/IndexConfig+in+SolrConfig ]