最近準備把一千九百多萬數據導入Solr中，在以前測試數據只有一兩百萬，全量導入沒有任務問題。但是，換成一千九百萬數據時，solr報內存異常(java.lang.OutOfMemoryError：GC overhead limit exceeded)，整個tomcat無法使用。我發現，我給tomcat最大堆內存512M。我覺得，可能是內存過小，于是，我把內存改大些，1024M（set JAVA_OPTS=-server -Xms1024m -Xmx1024m -XX:PermSize=128M -XX:MaxPermSize=256M）。結果，還是內存溢出。我想已經不是tomcat內存的問題（當然，如果你的內存足夠大，也是可行的）。問題，應該出在solr的dataimporthandler取數據那塊。solr除了內存溢出錯誤，還有其他異常：

Full Import failed:java.lang.RuntimeException: java.lang.RuntimeException: org.apache.solr.handler.dataimport.DataImportHandlerException: Unable to execute query: select * from POI PRocessing Document # 1at org.apache.solr.handler.dataimport.DocBuilder.execute(DocBuilder.java:278)at org.apache.solr.handler.dataimport.DataImporter.doFullImport(DataImporter.java:411)at org.apache.solr.handler.dataimport.DataImporter.runCmd(DataImporter.java:483)at org.apache.solr.handler.dataimport.DataImporter$1.run(DataImporter.java:464)Caused by: java.lang.RuntimeException: org.apache.solr.handler.dataimport.DataImportHandlerException: Unable to execute query: select * from POI Processing Document # 1at org.apache.solr.handler.dataimport.DocBuilder.buildDocument(DocBuilder.java:418)at org.apache.solr.handler.dataimport.DocBuilder.doFullDump(DocBuilder.java:331)at org.apache.solr.handler.dataimport.DocBuilder.execute(DocBuilder.java:239)... 3 moreCaused by: org.apache.solr.handler.dataimport.DataImportHandlerException: Unable to execute query: select * from POI Processing Document # 1at org.apache.solr.handler.dataimport.DataImportHandlerException.wrapAndThrow(DataImportHandlerException.java:71)at org.apache.solr.handler.dataimport.JdbcDataSource$ResultSetIterator.<init>(JdbcDataSource.java:281)at org.apache.solr.handler.dataimport.JdbcDataSource.getData(JdbcDataSource.java:238)at org.apache.solr.handler.dataimport.JdbcDataSource.getData(JdbcDataSource.java:42)at org.apache.solr.handler.dataimport.SqlEntityProcessor.initQuery(SqlEntityProcessor.java:59)at org.apache.solr.handler.dataimport.SqlEntityProcessor.nextRow(SqlEntityProcessor.java:73)at org.apache.solr.handler.dataimport.EntityProcessorWrapper.nextRow(EntityProcessorWrapper.java:243)at org.apache.solr.handler.dataimport.DocBuilder.buildDocument(DocBuilder.java:477)at org.apache.solr.handler.dataimport.DocBuilder.buildDocument(DocBuilder.java:416)... 5 moreCaused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failureThe last packet successfully received from the server was 395,021 milliseconds ago.  The last packet sent successfully to the server was 395,021 milliseconds ago.at sun.reflect.NativeConstructoraccessorImpl.newInstance0(Native Method)at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)at java.lang.reflect.Constructor.newInstance(Constructor.java:526)at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1074)at com.mysql.jdbc.MysqlIO.nextRowFast(MysqlIO.java:1653)at com.mysql.jdbc.MysqlIO.nextRow(MysqlIO.java:1409)at com.mysql.jdbc.MysqlIO.readSingleRowSet(MysqlIO.java:2883)at com.mysql.jdbc.MysqlIO.getResultSet(MysqlIO.java:476)at com.mysql.jdbc.MysqlIO.readResultsForQueryOrUpdate(MysqlIO.java:2576)at com.mysql.jdbc.MysqlIO.readAllResults(MysqlIO.java:1757)at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2167)at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2637)at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2566)at com.mysql.jdbc.StatementImpl.execute(StatementImpl.java:782)at com.mysql.jdbc.StatementImpl.execute(StatementImpl.java:625)at org.apache.solr.handler.dataimport.JdbcDataSource$ResultSetIterator.<init>(JdbcDataSource.java:274)... 12 moreCaused by: java.io.EOFException: Can not read response from server. Expected to read 39 bytes, read 30 bytes before connection was unexpectedly lost.at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2497)at com.mysql.jdbc.MysqlIO.nextRowFast(MysqlIO.java:1634)... 23 more

　　我搜索了一下Solr的wiki，了解到solr　jdbc取數據時，setBatchSize的問題。默認，會把很多數據放到內存中，這也是導致我的內存居高不下，后來導致內存溢出的原因。于是，我修改dataimporthandler配置文件：batchSize="-1" 解決內存溢出

　　配置文件修改如下：

　　　　　　<dataSource driver="com.mysql.jdbc.Driver" url="jdbc:mysql://localhost:3306/world" user="root" passWord="root" batchSize="-1" />

　　重啟一個solr的core，重新導入，問題解決。