Develop Reference

Working with MCRTsim simulator on a LINUX system

I am trying to use the MCRTsim simulator in my research work. As documented in https://resl.csie.nptu.edu.tw/dokuwiki/doku.php?id=guide, I run this command java -jar MCRTsim/dist/MCRTsim2.8.jar in specified directory, but the simulation window did not pop up. Instead, I got following exceptions:
Exception in thread "main" java.lang.NullPointerException
at java.base/java.io.Reader.<init>(Reader.java:167)
at java.base/java.io.InputStreamReader.<init>(InputStreamReader.java:109)
at org.apache.commons.io.IOUtils.copy(IOUtils.java:2440)
at org.apache.commons.io.IOUtils.toString(IOUtils.java:1084)
at org.apache.commons.io.IOUtils.toString(IOUtils.java:1110)
at userInterface.frontEnd.SimulationViewer.setComboBox(SimulationViewer.java:529)
at userInterface.frontEnd.SimulationViewer.initialize(SimulationViewer.java:359)
at userInterface.frontEnd.SimulationViewer.<init>(SimulationViewer.java:97)
at userInterface.UserInterface.initialize(UserInterface.java:45)
at userInterface.UserInterface.<init>(UserInterface.java:31)
at mcrtsim.MCRTsim.main(MCRTsim.java:55)
I am using Ubuntu system and JDK 11. I have not used Java much. I am not able to understand what this error is saying. Would anyone please help me with this?

Finally, I got the solution to this problem. I think this simulator is compatible with openjdk-8. So, I removed openjdk-11 from my system and installed openjdk-8.
After installing openjdk-8, I run the command java -jar dist/MCRTsim2.8.jar . This time I got the following error:
Exception in thread "main" java.awt.AWTError: Assistive Technology not
found: org.GNOME.Accessibility.AtkWrapper
at java.awt.Toolkit.loadAssistiveTechnologies(Toolkit.java:807)
at java.awt.Toolkit.getDefaultToolkit(Toolkit.java:886)
at java.awt.Window.getToolkit(Window.java:1358)
at java.awt.Window.init(Window.java:506)
at java.awt.Window.<init>(Window.java:537)
at java.awt.Frame.<init>(Frame.java:420)
at javax.swing.JFrame.<init>(JFrame.java:233)
at userInterface.UserInterface.initialize(UserInterface.java:37)
at userInterface.UserInterface.<init>(UserInterface.java:31)
at mcrtsim.MCRTsim.main(MCRTsim.java:55)
After that, I followed this blog https://askubuntu.com/questions/695560/assistive-technology-not-found-awterror to rectify the above error.
I just commented this line #assistive_technologies=org.GNOME.Accessibility.AtkWrapper in /etc/java-8-openjdk/accessibility.properties file.
And, it started working.

Jmeter error trying to record a sample java.lang.IllegalArgumentException: Failed marshalling

I have one Linux VPS dedicated just for running a jmeter. The tests run fine, but failed requests are not written to error.jtl with SimpleDataWriter. Java error is written to jmeter.log instead.
I run the tests in non-gui mode:
jmeter -n -t om5.jmx -j results-tmp1/t3-l1-jmeter.log
The error
2016/07/08 16:59:35 ERROR - jmeter.reporters.ResultCollector:
Error trying to record a sample java.lang.IllegalArgumentException: Failed marshalling:class:class
org.apache.jmeter.samplers.SampleResult,content:org.apache.jmeter.samplers.SampleResult#1f605bfa[saveConfig=org.apache.jmeter.samplers.SampleSaveConfiguration#b4a9237e,parent=<null>,
responseData={},responseCode=500,label=03 add to cart,resultFileName=,samplerData=<null>,threadName=Thread Group 1-149,responseMessage=Number of samples in transaction : 2, number of failing samples : 1,
responseHeaders=,contentType=,requestHeaders=,timeStamp=1467989884109,startTime=1467989884109,endTime=1467989975286,idleTime=1001,pauseTime=0,assertionResults=<null>,subResults=[reset basketItems, /some-page],
dataType=,success=false,files=[res-tmp/t400-l5-errors.jtl],dataEncoding=<null>,elapsedTime=90176,latency=0,connectTime=0,startNextThreadLoop=false,stopThread=false,stopTest=false,
stopTestNow=false,isMonitor=false,sampleCount=1,bytes=806,headersSize=192,bodySize=614,groupThreads=400,allThreads=400,nanoTimeOffset=1467988012523,useNanoTime=true,nanoThreadSleep=5000,location=<null>]
at org.apache.jmeter.save.SaveService.saveSampleResult(SaveService.java:345)
at org.apache.jmeter.reporters.ResultCollector.sampleOccurred(ResultCollector.java:557)
at org.apache.jmeter.threads.ListenerNotifier.notifyListeners(ListenerNotifier.java:67)
at org.apache.jmeter.threads.JMeterThread.notifyListeners(JMeterThread.java:819)
at org.apache.jmeter.threads.JMeterThread.doEndTransactionSampler(JMeterThread.java:534)
at org.apache.jmeter.threads.JMeterThread.triggerEndOfLoopOnParentControllers(JMeterThread.java:342)
at org.apache.jmeter.threads.JMeterThread.run(JMeterThread.java:258)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
I cannot find what is wrong. It is only that one machine, that gives me this error. Everywhere else I try it, it works correctly.
The OS is Debian Jessie (8.5) - minimal from official repositories. I tried many different versions of java (1.7, 1.8) - currently running on the latest 1.8 (1.8.0_92-b14) and I have the latest apache-jmeter 3.0 r1743807, but previously I used 2.13 r1665067. I don't use any third-party plugins.
I didn't notice exactly when it stopped working, what change was done (some os update, maybe some change in jmx), but I have my tests in git, so I checked out older version from the date of my last full error.jtl and it is not writing the errors to jtl as well.
I reinstalled the Debian to Ubuntu 16.04 and nothing changed.
I don't know how to debug that problem, what should I do, because on any other machine I have an access to, it works fine.

I don't know if you've fixed this problem until now?
I had the same issue, and I fixed it just now.
I guess in your jmeter script, you checked the hostname to record sample result, in jmeter.log, you could find such message: jmeter couldn't get the linux Local IP, so hostname is Null, exception threw out.
So what you need to do is remove 'Save Hostname' from 'Sample Result Save Configuration' tab.

Solr stopped with Error opening new searcher at org.apache.solr.core

Yesterday suddenly our solr server got stopped with following exception
org.apache.solr.common.SolrException: Error opening new searcher at
org.apache.solr.core.SolrCore.openNewSearcher(SolrCore.java:1438) at
org.apache.solr.core.SolrCore.getSearcher(SolrCore.java:1550) at
org.apache.solr.core.SolrCore.getSearcher(SolrCore.java:1319) at
org.apache.solr.update.DirectUpdateHandler2.commit(DirectUpdateHandler2.java:574)
at
org.apache.solr.update.processor.RunUpdateProcessor.processCommit(RunUpdateProcessorFactory.java:95)
at
org.apache.solr.update.processor.UpdateRequestProcessor.processCommit(UpdateRequestProcessor.java:64)
at
org.apache.solr.update.processor.DistributedUpdateProcessor.processCommit(DistributedUpdateProcessor.java:1147)
at
org.apache.solr.update.processor.LogUpdateProcessor.processCommit(LogUpdateProcessorFactory.java:157)
at
org.apache.solr.handler.loader.XMLLoader.processUpdate(XMLLoader.java:266)
at org.apache.solr.handler.loader.XMLLoader.load(XMLLoader.java:173)
at
org.apache.solr.handler.UpdateRequestHandler$1.load(UpdateRequestHandler.java:92)
Caused by: java.io.IOException: Map failed at
sun.nio.ch.FileChannelImpl.map(FileChannelImpl.java:889) at
org.apache.lucene.store.MMapDirectory.map(MMapDirectory.java:283) at
org.apache.lucene.store.MMapDirectory$MMapIndexInput.
But at that time we have lot of memory left in that server. Any guess?

Assuming its a linux system you can try ulimit -v unlimited
Check the below links for more information.
https://support.lucidworks.com/hc/en-us/articles/206127457-Caused-by-java-io-IOException-Map-failed
https://stackoverflow.com/a/8893684/689625
You will get answers much faster if you include more information, like the version of your software (in this case solr version), OS Name and version, Java version etc.

The flag -fix didn't work in my later version, instead I used exorcise
java -cp lucene-core-5.5.0.jar -ea:org.apache.lucene... org.apache.lucene.index.CheckIndex PATH_TO_INDEX -exorcise
I hope this could help.

I got this error:
Error creating core [mm_shard1_replica1]: Error opening new searcher
and tried fiddling with ulimit and max_map_count
In the end it turned out to be a bad error message because the problem turned out to be a corrupt index.
Fixed it by shutting down solr and doing this:
cd /var/lib/solr/example/solr-webapp/webapp/WEB-INF/lib
java -cp lucene-core-4.10.4.jar -ea:org.apache.lucene... org.apache.lucene.index.CheckIndex /path/to/index -fix
To just check wether the index is broken remove the -fix at the end of above command. After that I started up solr and it recreated its index from the rest of the solrcloud cluster.

Use sqlite with Java on Raspberry pi

I have created small code of sqlite database in java.
Below is the code for connection with database,
Class.forName("org.sqlite.JDBC");
objConnection=DriverManager.getConnection("jdbc:sqlite:/etc/javaData/Test.db");
In this code the exception thrown in second line for getConnection(). I am trying this code on Raspberry pi. How to fix the exceptionrelated to this
Exception
SQLITE addDeviceInfo()-[SQLITE] SQL Exception occured. RetryCount:1 (MAX Retry: 2) ErrorCode: 27154 Exception Message: Error opening connection Stack Trace: java.sql.SQLException: Error opening connection
at org.sqlite.core.CoreConnection.open(CoreConnection.java:140)
at org.sqlite.core.CoreConnection.<init>(CoreConnection.java:66)
at org.sqlite.jdbc3.JDBC3Connection.<init>(JDBC3Connection.java:21)
at org.sqlite.jdbc4.JDBC4Connection.<init>(JDBC4Connection.java:23)
at org.sqlite.SQLiteConnection.<init>(SQLiteConnection.java:45)
at org.sqlite.JDBC.createConnection(JDBC.java:114)
at org.sqlite.JDBC.connect(JDBC.java:88)
at java.sql.DriverManager.getConnection(DriverManager.java:571)
at java.sql.DriverManager.getConnection(DriverManager.java:215)
at kmbt.DCA.SQLite.DCASQLiteUtility.getSQliteConnection(DCASQLiteUtility.java:152)
at kmbt.DCA.SQLite.ManagedDeviceSetting.SQLite_ManagedDeviceSettingManager.addDeviceInfo(SQLite_ManagedDeviceSettingManager.java:981)
at kmbt.DCA.DCAChildProcessMng.InitManagedDeviceInfo(DCAChildProcessMng.java:5726)
at kmbt.DCA.DCAChildProcessMng.InitSQLite(DCAChildProcessMng.java:4387)
at kmbt.DCA.DCAChildProcessMng.start(DCAChildProcessMng.java:365)
at kmbt.DCA.DCAChildProcess.main(DCAChildProcess.java:23)
Caused by: java.lang.Exception: Error loading native library: /org/sqlite/native/Linux/arm/libsqlitejdbc.so
at org.sqlite.SQLiteJDBCLoader.loadSQLiteNativeLibrary(SQLiteJDBCLoader.java:243) at org.sqlite.SQLiteJDBCLoader.initialize(SQLiteJDBCLoader.java:65)
at org.sqlite.core.NativeDB.load(NativeDB.java:53)
at org.sqlite.core.CoreConnection.open(CoreConnection.java:136)
... 14 more

Your code seems correct and the exception thrown seems don't have nothing to do with some library's problem.
The only thing that sound me a little bit strange, is that you put your database in /etc folder. First of all it is not very correct, because the /etc folder is used to store config file and not data. In addition to this, maybe there could be some kind of issue with r/w folder's permissions. Try to move your database to your home directory or to other any directory owned by your user and not from root.
Hope this will be usefull for you.
-- EDIT --
Ok, the problem is that you have downloaded the wrong library:
Error loading native library: /org/sqlite/native/Linux/arm/libsqlitejdbc.so
You have to use the ARM build of the sqlite library. Try to take a look at this:
Error opening connection SQLite on Raspberry pi
and this: Sqlite4java on Raspberry Pi

I also faced java.lang.Exception: Error loading native library: /org/sqlite/native/Linux/arm/libsqlitejdbc.so
Looking into sqlite-jdbc-3.8.6.jar I found that /org/sqlite/native/Linux/ contains no arm folder -> sqlite is not compiled for arm.
With these changes I've managed to build on the pi: https://bitbucket.org/kidmose/sqlite-jdbc/commits/cb7a7ef62c034938e8ecb737b148e5c80877c083
pi#raspberry ~/sqlite-jdbc $ export JAVA_HOME=/usr/lib/jvm/jdk-7-oracle-armhf/
pi#raspberry ~/sqlite-jdbc $ chmod 755 ./amalgamation_version.sh
pi#raspberry ~/sqlite-jdbc $ make
Replacing the old jar with the newly built one solved my problem.
All credit goes to: https://pidome.wordpress.com/2013/10/01/java-goes-hard-on-the-raspberry-pi-so-does-pidome/

Sqlite java.lang.UnsatisfiedLinkError in linux

I have a program that uses Sqlite database. It works fine on Windows (exported jar or directly in Eclipse) but when I move it to linux server (plan is to use run it at certain intervals, cron job). I'm exporting it to jar from Eclipse and packing the sqlite-jdbc4-3.8.2-SNAPSHOT.jar with it. Error is this:
/$ /usr/bin/java -jar /home/username/Software.jar /home/username/
java.lang.UnsatisfiedLinkError: /tmp/sqlite-3.8.2-amd64-libsqlitejdbc.so: /tmp/sqlite-3.8.2-amd64-libsqlitejdbc.so: failed to map segment from shared object: Operation not permitted
Exception in thread "main" java.lang.UnsatisfiedLinkError: org.sqlite.core.NativeDB._open(Ljava/lang/String;I)V
at org.sqlite.core.NativeDB._open(Native Method)
at org.sqlite.core.DB.open(DB.java:161)
at org.sqlite.core.CoreConnection.open(CoreConnection.java:145)
at org.sqlite.core.CoreConnection.<init>(CoreConnection.java:66)
at org.sqlite.jdbc3.JDBC3Connection.<init>(JDBC3Connection.java:21)
at org.sqlite.jdbc4.JDBC4Connection.<init>(JDBC4Connection.java:23)
at org.sqlite.SQLiteConnection.<init>(SQLiteConnection.java:44)
at org.sqlite.JDBC.createConnection(JDBC.java:113)
at org.sqlite.JDBC.connect(JDBC.java:87)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:207)
....
So before you ask, I've made sure that sqlite-3.8.2-amd64-libsqlitejdbc.so in /tmp/ has all permissions (rwxrwxrwx). Still that native library is causing problems. It does get copied in /tmp/ folder though. That being said I totally suck in Linux... and for that reason I'm pretty much clueless what to try next.
What should I do? Switch connector?
EDIT:
Solved the problem by using System.setProperty("java.io.tmpdir", "/home/username/"); Apparently it for some reason couldn't execute the native library from tmp folder... Probably because it was created by root. Also I had to revert back to sqlite-jdbc-3.7.2.jar because the new one crashes on linux.

I had same problem, and I found the solution in this GitHub issue:
JAVA_OPTS=-Djava.io.tmpdir=/path/to/some/other/tmpdir bin/cerebro
Also look at this other SO answer.