enhanced memory protection and OOM exception handling in Solr connector

source/net/yacy/cora/federate/solr/connector/ConcurrentUpdateSolrConnector.java

@@ -109,9 +109,17 @@ public class ConcurrentUpdateSolrConnector implements SolrConnector {
                     } else {
                         // if there is only a single document, send this directly to solr
                         //ConcurrentLog.info("ConcurrentUpdateSolrConnector", "sending one document to solr");
+                        updateIdCache((String) doc.getFieldValue(CollectionSchema.id.getSolrFieldName()));
                         try {
-                            updateIdCache((String) doc.getFieldValue(CollectionSchema.id.getSolrFieldName()));
                             ConcurrentUpdateSolrConnector.this.connector.add(doc);
+                        } catch (final OutOfMemoryError e) {
+                            // clear and try again...
+                            clearCaches();
+                            try {
+                                ConcurrentUpdateSolrConnector.this.connector.add(doc);
+                            } catch (final IOException ee) {
+                                ConcurrentLog.logException(e);
+                            }
                         } catch (final IOException e) {
                             ConcurrentLog.logException(e);
                         }

source/net/yacy/cora/federate/solr/connector/EmbeddedSolrConnector.java

@@ -38,6 +38,7 @@ import net.yacy.search.schema.CollectionSchema;
 import org.apache.lucene.document.Document;
 import org.apache.lucene.index.DirectoryReader;
 import org.apache.lucene.index.IndexableField;
+import org.apache.lucene.search.FieldCache;
 import org.apache.lucene.search.Query;
 import org.apache.lucene.util.BytesRef;
 import org.apache.solr.client.solrj.SolrQuery;
@@ -133,7 +134,7 @@ public class EmbeddedSolrConnector extends SolrServerConnector implements SolrCo
             // clear 'lost' caches
             if (ib instanceof SolrCache) ((SolrCache<?,?>) ib).clear();
         }
-        // this.core.getInfoRegistry().clear();
+        FieldCache.DEFAULT.purgeAllCaches(); // purge the lucene field cache
     }
     
     public SolrInstance getInstance() {

source/net/yacy/cora/federate/solr/connector/SolrServerConnector.java

@@ -71,6 +71,7 @@ public abstract class SolrServerConnector extends AbstractSolrConnector implemen
     
     @Override
     public void commit(final boolean softCommit) {
+        if (this.server == null) return;
         synchronized (this.server) {
             try {
                 this.server.commit(true, true, softCommit);