Sunspot Solr on Ruby: "Exception writing document id to the index, java.lang.OutOfMemoryError"

Question

We have a Ruby on Rails application running for some time now, but since a couple of days we're just getting a HTTP500 Error while trying to update any documents. The system is running Ruby 1.9.3 with unicorn 4.8.2 and nginx 1.2.1 and a sunspot_solr 2.1.1 gem for the search index (besides some others).

The Production log tells me that every time someone tries to create or update a document the solr server throws a bunch of errors. The most prominent I think is this one:

org.apache.solr.update.DirectUpdateHandler2.addDoc(DirectUpdateHandler2.java:164)\n\t... 30 more\nCaused by: java.lang.OutOfMemoryError: Java heap space\n\

Unfortunately nothing changes if i edit config/sunstpot.yml to include "max_memory: 1G":

production:
   solr:
    hostname: localhost
    port: 8080
    log_level: WARNING
    min_memory: 32M
    max_memory: 1G
    path: /solr-4.10.2/default #production #ollection1 #production

Here is the complete production.log entry:

[a086bc878daa0abd367379daade96682] Completed 500 Internal Server Error in 195ms
[a086bc878daa0abd367379daade96682] 
RSolr::Error::Http (RSolr::Error::Http - 500 Internal Server Error
Error: {"responseHeader":{"status":500,"QTime":2},"error":{"msg":"Exception writing document id Neuigkeit 393 to the index; possible analysis error.","trace":"org.apache.solr.common.SolrException: Exception writing document id Neuigkeit 393 to the index; possible analysis error.\n\
org.apache.solr.update.DirectUpdateHandler2.addDoc(DirectUpdateHandler2.java:168)\n\
org.apache.solr.update.processor.RunUpdateProcessor.processAdd(RunUpdateProcessorFactory.java:69)\n\tat
org.apache.solr.update.processor.UpdateRequestProcessor.processAdd(UpdateRequestProcessor.java:51)\n\tat
org.apache.solr.update.processor.DistributedUpdateProcessor.doLocalAdd(DistributedUpdateProcessor.java:926)\n\tat
org.apache.solr.update.processor.DistributedUpdateProcessor.versionAdd(DistributedUpdateProcessor.java:1080)\n\tat
org.apache.solr.update.processor.DistributedUpdateProcessor.processAdd(DistributedUpdateProcessor.java:692)\n\tat
org.apache.solr.update.processor.LogUpdateProcessor.processAdd(LogUpdateProcessorFactory.java:100)\n\
org.apache.solr.handler.loader.XMLLoader.processUpdate(XMLLoader.java:247)\n\tat
org.apache.solr.handler.loader.XMLLoader.load(XMLLoader.java:174)\n\
org.apache.solr.handler.UpdateRequestHandler$1.load(UpdateRequestHandler.java:99)\n\tat
org.apache.solr.haa086bc878daa0abd367379daade96682] Completed 500 Internal Server Error in 195ms
[a086bc878daa0abd367379daade96682] 
RSolr::Error::Http (RSolr::Error::Http - 500 Internal Server Error
Error: {"responseHeader":{"status":500,"QTime":2},"error":{"msg":"Exception writing document id Neuigkeit 393 to the index; possible analysis error.","trace":"org.apache.solr.common.SolrException: Exception writing document indler.ContentStreamHandlerBase.handleRequestBody(ContentStreamHandlerBase.java:74)\n\
org.apache.solr.handler.RequestHandlerBase.handleRequest(RequestHandlerBase.java:135)\n\
org.apache.solr.core.SolrCore.execute(SolrCore.java:1967)\n\
org.apache.solr.servlet.SolrDispatchFilter.execute(SolrDispatchFilter.java:777)\n\
org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:418)\n\
org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:207)\n\
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)\n\
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)\n\
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225)\n\
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)\n\
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)\n\
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)\n\
org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)\n\
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)\n\
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)\n\
org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1003)\n\
org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:579)\n\
org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)\n\
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)\n\
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)\n\
java.lang.Thread.run(Thread.java:745)\nCaused by: org.apache.lucene.store.AlreadyClosedException: this IndexWriter is closed\n\
org.apache.lucene.index.IndexWriter.ensureOpen(IndexWriter.java:698)\n\
org.apache.lucene.index.IndexWriter.ensureOpen(IndexWriter.java:712)\n\
org.apache.lucene.index.IndexWriter.updateDocument(IndexWriter.java:1507)\n\
org.apache.solr.update.DirectUpdateHandler2.addDoc0(DirectUpdateHandler2.java:240)\n\
org.apache.solr.update.DirectUpdateHandler2.addDoc(DirectUpdateHandler2.java:164)\n\t... 30 more\nCaused by: java.lang.OutOfMemoryError: Java heap space\n\
org.apache.lucene.index.FreqProxTermsWriterPerField$FreqProxPostingsArray.<init>(FreqProxTermsWriterPerField.java:207)\n\
org.apache.lucene.index.FreqProxTermsWriterPerField$FreqProxPostingsArray.newInstance(FreqProxTermsWriterPerField.java:230)\n\
org.apache.lucene.index.ParallelPostingsArray.grow(ParallelPostingsArray.java:48)\n\
org.apache.lucene.index.TermsHashPerField$PostingsBytesStartArray.grow(TermsHashPerField.java:252)\n\
org.apache.lucene.util.BytesRefHash.add(BytesRefHash.java:292)\n\
org.apache.lucene.index.TermsHashPerField.add(TermsHashPerField.java:151)\n\
org.apache.lucene.index.DefaultIndexingChain$PerField.invert(DefaultIndexingChain.java:659)\n\
org.apache.lucene.index.DefaultIndexingChain.processField(DefaultIndexingChain.java:359)\n\
org.apache.lucene.index.DefaultIndexingChain.processDocument(DefaultIndexingChain.java:318)\n\
org.apache.lucene.index.DocumentsWriterPerThread.updateDocument(DocumentsWriterPerThread.java:239)\n\
org.apache.lucene.index.DocumentsWriter.updateDocument(DocumentsWriter.java:454)\n\
org.apache.lucene.index.IndexWriter.updateDocument(IndexWriter.java:1511)\n\
org.apache.solr.update.DirectUpdateHandler2.addDoc0(DirectUpdateHandler2.java:240)\n\
org.apache.solr.update.DirectUpdateHandler2.addDoc(DirectUpdateHandler2.java:164)\n\
org.apache.solr.update.processor.RunUpdateProcessor.processAdd(RunUpdateProcessorFactory.java:69)\n\
org.apache.solr.update.processor.UpdateRequestProcessor.processAdd(UpdateRequestProcessor.java:51)\n\
org.apache.solr.update.processor.DistributedUpdateProcessor.doLocalAdd(DistributedUpdateProcessor.java:926)\n\
org.apache.solr.update.processor.DistributedUpdateProcessor.versionAdd(DistributedUpdateProcessor.java:1080)\n\
org.apache.solr.update.processor.DistributedUpdateProcessor.processAdd(DistributedUpdateProcessor.java:692)\n\
org.apache.solr.update.processor.LogUpdateProcessor.processAdd(LogUpdateProcessorFactory.java:100)\n\
org.apache.solr.handler.loader.XMLLoader.processUpdate(XMLLoader.java:247)\n\
org.apache.solr.handler.loader.XMLLoader.load(XMLLoader.java:174)\n\
org.apache.solr.handler.UpdateRequestHandler$1.load(UpdateRequestHandler.java:99)\n\
org.apache.solr.handler.ContentStreamHandlerBase.handleRequestBody(ContentStreamHandlerBase.java:74)\n\
org.apache.solr.handler.RequestHandlerBase.handleRequest(RequestHandlerBase.java:135)\n\
org.apache.solr.core.SolrCore.execute(SolrCore.java:1967)\n\
org.apache.solr.servlet.SolrDispatchFilter.execute(SolrDispatchFilter.java:777)\n\
org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:418)\n\
org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:207)\n\
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)\n\
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)\n\
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225)\n","code":500}}
URI: http://localhost:8080/solr-4.10.2/default/update?wt=json

EDIT: I'm an idiot. The solr server isn't contained in the unicorn service. Restarting it via 'service tomcat7 restart' loaded the updated config/sunstpot.yml and solved the problem.