HBase NoServerForRegionException

We have met following error:

12/12/10 12:17:57 INFO ipc.HBaseRPC: Server at xxxxx/172.22.245.48:60020 could not be reached after 1 tries, giving up.
12/12/10 12:17:59 INFO ipc.HBaseRPC: Server at xxxxx/172.22.245.48:60020 could not be reached after 1 tries, giving up.
12/12/10 12:18:01 INFO ipc.HBaseRPC: Server at xxxxx/172.22.245.48:60020 could not be reached after 1 tries, giving up.
12/12/10 12:18:03 INFO ipc.HBaseRPC: Server at xxxxx/172.22.245.48:60020 could not be reached after 1 tries, giving up.
12/12/10 12:18:06 INFO ipc.HBaseRPC: Server at xxxxx/172.22.245.48:60020 could not be reached after 1 tries, giving up.
12/12/10 12:18:09 INFO ipc.HBaseRPC: Server at xxxxx/172.22.245.48:60020 could not be reached after 1 tries, giving up.
12/12/10 12:18:14 INFO ipc.HBaseRPC: Server at xxxxx/172.22.245.48:60020 could not be reached after 1 tries, giving up.

ERROR: org.apache.hadoop.hbase.client.NoServerForRegionException: Unable to find region for stats,,99999999999999 after 7 tries.

In other words it means that region server is not reachable. There is closes information about reason why it's not accessible. When you look in HBase master status server should be listed in dead regions server:

Solution is to check connection to region server. When it's correct restart HBase.

Doxia sink Exception

Following exception appears during site generating.

[INFO] Skipped "About" report, file "index.html" already exists for the English version.
[INFO] Generating "Distribution Management" report.
[WARNING] Deprecated API called - not org.apache.maven.doxia.sink.Sink instance and no SinkFactory available. Please update this plugin.
[INFO] Generating "Issue Tracking" report.
[WARNING] Deprecated API called - not org.apache.maven.doxia.sink.Sink instance and no SinkFactory available. Please update this plugin.
[INFO] Generating "Project Team" report.
[WARNING] Deprecated API called - not org.apache.maven.doxia.sink.Sink instance and no SinkFactory available. Please update this plugin.
[INFO] Generating "Dependency Management" report.
[WARNING] Deprecated API called - not org.apache.maven.doxia.sink.Sink instance and no SinkFactory available. Please update this plugin.
[INFO] ------------------------------------------------------------------------
[ERROR] FATAL ERROR
[INFO] ------------------------------------------------------------------------
[INFO] 1
[INFO] ------------------------------------------------------------------------
[INFO] Trace
java.lang.ArrayIndexOutOfBoundsException: 1
 at org.apache.maven.doxia.module.xhtml.XhtmlSink.tableCell(XhtmlSink.java:791)
 at org.apache.maven.doxia.module.xhtml.XhtmlSink.tableHeaderCell(XhtmlSink.java:777)
 at org.apache.maven.reporting.AbstractMavenReportRenderer.tableHeaderCell(AbstractMavenReportRenderer.java:267)
 at org.apache.maven.reporting.AbstractMavenReportRenderer.tableHeader(AbstractMavenReportRenderer.java:356)
 at org.apache.maven.report.projectinfo.dependencies.renderer.DependencyManagementRenderer.renderDependenciesForScope(DependencyManagementRenderer.java:203)
 at org.apache.maven.report.projectinfo.dependencies.renderer.DependencyManagementRenderer.renderDependenciesForAllScopes(DependencyManagementRenderer.java:158)
 at org.apache.maven.report.projectinfo.dependencies.renderer.DependencyManagementRenderer.renderSectionProjectDependencies(DependencyManagementRenderer.java:149)
 at org.apache.maven.report.projectinfo.dependencies.renderer.DependencyManagementRenderer.renderBody(DependencyManagementRenderer.java:135)
 at org.apache.maven.reporting.AbstractMavenReportRenderer.render(AbstractMavenReportRenderer.java:79)
 at org.apache.maven.report.projectinfo.DependencyManagementReport.executeReport(DependencyManagementReport.java:112)
 at org.apache.maven.reporting.AbstractMavenReport.generate(AbstractMavenReport.java:190)
 at org.apache.maven.reporting.AbstractMavenReport.generate(AbstractMavenReport.java:144)
 at org.apache.maven.plugins.site.ReportDocumentRenderer.renderDocument(ReportDocumentRenderer.java:139)
 at org.apache.maven.doxia.siterenderer.DefaultSiteRenderer.renderModule(DefaultSiteRenderer.java:269)
 at org.apache.maven.doxia.siterenderer.DefaultSiteRenderer.render(DefaultSiteRenderer.java:101)
 at org.apache.maven.plugins.site.SiteMojo.renderLocale(SiteMojo.java:133)
 at org.apache.maven.plugins.site.SiteMojo.execute(SiteMojo.java:100)
 at org.apache.maven.plugin.DefaultPluginManager.executeMojo(DefaultPluginManager.java:490)
 at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoals(DefaultLifecycleExecutor.java:694)
 at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoalWithLifecycle(DefaultLifecycleExecutor.java:556)
 at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoal(DefaultLifecycleExecutor.java:535)
 at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoalAndHandleFailures(DefaultLifecycleExecutor.java:387)
 at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeTaskSegments(DefaultLifecycleExecutor.java:348)
 at org.apache.maven.lifecycle.DefaultLifecycleExecutor.execute(DefaultLifecycleExecutor.java:180)
 at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:328)
 at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:138)
 at org.apache.maven.cli.MavenCli.main(MavenCli.java:362)
 at org.apache.maven.cli.compat.CompatibleMain.main(CompatibleMain.java:60)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:597)
 at org.codehaus.classworlds.Launcher.launchEnhanced(Launcher.java:315)
 at org.codehaus.classworlds.Launcher.launch(Launcher.java:255)
 at org.codehaus.classworlds.Launcher.mainWithExitCode(Launcher.java:430)
 at org.codehaus.classworlds.Launcher.main(Launcher.java:375)

Problem is in maven project info plugin version. When version is 2.1 or lover problem disappears.

Plugin could be configured like this:

<project>
  ...
  <reporting>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-project-info-reports-plugin</artifactId>
        <version>2.1</version>
        ...
      </plugin>
      ...
    </plugins>
  </reporting>
  ...
</project>

Root of the problem is in version of module doxia-sink-api module which is different in both versions of project info plugin version. In version 1.1 is doxia-sink-api-1.0-alpha-11 and in version 2.2 is doxia-sink-api-1.2.

When you have in pom file dependency on javadoc plugin which itself contains dependency on doxia-sink-api-1.0-alpha-11 than in runtime doxia-sink-api version in project-info-plugin is overridden by version of doxia-sink-api from java doc plugin. So another solution is to upgrade java doc plugin or maven site plugin.

Maven - slow generating "Dependencies" report.

sometimes we have encountered very slow generating of maven site at first glance process was slow down by generating dependency report.

[INFO] Skipped "About" report, file "index.html" already exists for the English version.
[INFO] Generating "Issue Tracking" report.
[INFO] Generating "Project Team" report.
[INFO] Generating "Dependency Management" report.
[INFO] Generating "Dependencies" report.
[ERROR] Unable to determine if resource cglib:cglib:jar:2.0.2:compile exists in http://repo1.maven.org/maven2
[ERROR] Unable to determine if resource commons-collections:commons-collections:jar:2.1.1:compile exists in http://repo1.maven.org/maven2
[ERROR] Unable to determine if resource commons-logging:commons-logging:jar:1.0.4:compile exists in http://repo1.maven.org/maven2
[ERROR] Unable to determine if resource cz.xxxxx.xxx.xxx:xxx:jar:1.0.0:compile exists in http://repo1.maven.org/maven2

Problem is in maven dependency plugin. Which try to locate in which repository is artefact located. When there is no valid internet connection (e.g. you use firewall) problem could appears.
If it's your problem there is few ways how to fix it:

1. add runtime property

dependency.locations.enabled=false in commando line like this:

mvn -Ddependency.locations.enabled=false site

2. change pom.xml

or in pom.xml in plugin configuration:

<project>
  ...
  <reporting>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-project-info-reports-plugin</artifactId>
        <version>2.6</version>
        <configuration>
          <dependencyLocationsEnabled>
            false
          </dependencyLocationsEnabled>
        </configuration>
      </plugin>
      ...
    </plugins>
  </reporting>
  ...
</project>

3. Run site goal in offline mode

Even build site in offline mode like this:

mvn -o site

In that case you'll see following message in logs:

[WARNING] The parameter 'dependencyLocationsEnabled' is ignored in offline mode.

DbUnit teardown exception

Recently new problem appears in JUnit test logs:

com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Cannot truncate a table referenced in a foreign key constraint (`cub_test`.`api_month_stat`, CONSTRAINT `api_month_stat_access` FOREIGN KEY (`id_api_access`) REFERENCES `cub_test`.`api_access` (`id_api_access`))
 at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
 at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
 at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
 at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
 at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
 at com.mysql.jdbc.Util.getInstance(Util.java:381)
 at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1030)
 at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)
 at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3491)
 at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3423)
 at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1936)
 at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2060)
 at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2536)
 at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2465)
 at com.mysql.jdbc.StatementImpl.execute(StatementImpl.java:734)
 at com.mchange.v2.c3p0.impl.NewProxyStatement.execute(NewProxyStatement.java:1006)
 at org.dbunit.database.statement.SimpleStatement.executeBatch(SimpleStatement.java:66)
 at org.dbunit.operation.DeleteAllOperation.execute(DeleteAllOperation.java:122)
 at org.dbunit.operation.TruncateTableOperation.execute(TruncateTableOperation.java:84)
 at org.dbunit.AbstractDatabaseTester.executeOperation(AbstractDatabaseTester.java:179)
 at org.dbunit.AbstractDatabaseTester.onTearDown(AbstractDatabaseTester.java:82)
 at org.dbunit.DatabaseTestCase.tearDown(DatabaseTestCase.java:146)

When I tried to perform manually tear down operation truncate on table following problem appears:

mysql> truncate table api_access;
ERROR 1701 (42000): Cannot truncate a table referenced in a foreign key constraint (`cub_test`.`api_month_stat`, CONSTRAINT `api_month_stat_access` FOREIGN KEY (`id_api_access`) REFERENCES `cub_test`.`api_access` (`id_api_access`))
mysql> 

Problem is closely described at http://dev.mysql.com/doc/refman/5.0/en/truncate-table.html. In our case was solution to use "DELETE_ALL" as tear down operation. Tear down operation define what happen when test is executed. It could loo like:

    @Override
    protected DatabaseOperation getTearDownOperation() throws Exception {
 return DatabaseOperation.DELETE_ALL;
    }

Hibernate problem

We have met following problem in JUnit logs:

2012.11.28.22.42.45 ERROR hibernate.tool.hbm2ddl.SchemaUpdate - Unsuccessful: create table api_access (id_api_access integer not null, id_user integer not null, month_limit integer, api_key varchar(250), primary key (id_api_access)) type=InnoDB
2012.11.28.22.42.45 ERROR hibernate.tool.hbm2ddl.SchemaUpdate - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'type=InnoDB' at line 1

Problem is that hibernate use invalid dialect. In hibernate configuration property hibernate.dialect should have value org.hibernate.dialect.MySQL5InnoDBDialect.

How to display code listing at blogger.com

I found few articles about adding syntax highlighting to blogger.com. All of them was based on Java Script library SyntaxHighlighter. All post describe old version of SyntaxHighlighter. Because I had to play little bit with here is short guide how to use it.
First go to blog administration interface. Than choose "Template" and "Edit HTML". Than adjust HTML template just before closing head tag as it's on next snippet:

<head>

    ...

    <script src='http://alexgorbatchev.com/pub/sh/current/scripts/shCore.js' type='text/javascript'/>
    <link href='http://alexgorbatchev.com/pub/sh/current/styles/shCore.css' rel='stylesheet' type='text/css'/>

    <script src='http://alexgorbatchev.com/pub/sh/current/scripts/shBrushJava.js' type='text/javascript'/>
    <script src='http://alexgorbatchev.com/pub/sh/current/scripts/shBrushPlain.js' type='text/javascript'/>
    <script src='http://alexgorbatchev.com/pub/sh/current/scripts/shBrushXml.js' type='text/javascript'/>

    <link href='http://alexgorbatchev.com/pub/sh/current/styles/shThemeDefault.css' rel='stylesheet' type='text/css'/>

</head>

Adjust HTML template before closing body tag as it's on next snippet:

</body>

   ...

   <script type='text/javascript'>
       SyntaxHighlighter.all()
   </script>

</body>

Now close and save HTML template. Open new post and switch to "HTML" editing. Write post with following content:

<pre class="brush:java">
public void hello(final String name){  
    System.out.println("Hello " + name);  
}
</pre>

If is everything fine than you should see:

public void hello(final String name){  
    System.out.println("Hello " + name);  
}

When XML or HTML have to be displayed and highlighted it have to written in post with HTML entities. To find proper tool try google search for "encode html to entities".

How to use public maven repository

Nexus started provide maven repository for free.  It's also for non-opensource projects.

All information how to participate are at https://docs.sonatype.org/display/Repository/Sonatype+OSS+Maven+Repository+Usage+Guide#SonatypeOSSMavenRepositoryUsageGuide-7a.1.POMandsettingsconfig

Carefully go through all steps. For releasing in staging repository you artifacts have to be signed. There is also nice article how to do that at https://docs.sonatype.org/display/Repository/How+To+Generate+PGP+Signatures+With+Maven