If your server suddenly starts consuming too much resources (CPU, memory) despite having been working well before, it might be because of running the internal Derby DB. Typically, causes are incorrect/incomplete shutdown of Apache Tomcat and parallel (re)start of Apache Tomcat.

Solution: move to a standard (standalone) database.

How to fix this? Redeploy CloverETL Server:

If you are getting this error message during an attempt to start your application server (mostly Tomcat), perform the following actions.

Linux:

This command will help you set a path to the variable on the server.

As a final step, restart the application server.

Windows OS:

Set JAVA_HOME to your JDK installation directory, e.g. C:\Program Files\java\jdk1.8.0.

	Important
	Some CloverETL functions requires JDK to work correctly, therefore we do not recommend having only JRE installed.

Tomcat may sometimes ignore some context parameters. It may cause weird CloverETL Server behavior, since it appears as configured, but only partially. Some parameters are accepted, some are ignored. This issue is rare, however it may occur in some environments. Such behavior is consistent, so restart has no effect. It's possibly related to Tomcat issues: https://issues.apache.org/bugzilla/show_bug.cgi?id=47516 and https://issues.apache.org/bugzilla/show_bug.cgi?id=50700 To avoid this, please use a properties file instead of context parameters to configure CloverETL Server.

Tomcat start batch files for Windows aren't configured to create catalina.out file which contains standard output of the application. The catalina.out file may be vital when Tomcat isn't started in the console and an issue occurs. Or even when Tomcat is executed in the console, it may be closed automatically just after the error message appears in it.

Please follow these steps to enable catalina.out creation:

Then use the new startup file instead of [Tomcat_home]/bin/startup.bat.

If you get the Jetty application server successfully running but cannot start CloverETL Server, it might be because of the wrapper waiting for JVM too long (it is considered a low-memory issue). Examine [Jetty_home]\logs\jetty-service.log for a following line:

Startup failed: Timed out waiting for signal from JVM. 
      

If it is there, edit [Jetty_home]\bin\jetty-service.conf and add these lines:

wrapper.startup.timeout=60
wrapper.shutdown.timeout=60 
      

If that does not help either, try setting 120 for both values. Default timeouts are 30.

If you are deploying clover.war on the IBM WebSphere server without context path specified, be sure to check whether it is the only application running in the context root. If you cannot start CloverETL Server on WebSphere, check the log and look for a following message:

	  com.ibm.ws.webcontainer.exception.WebAppNotLoadedException: 
	  Failed to load webapp: Failed to load webapp: Context root /* is already bound. 
	  Cannot start application CloverETL
	  

If you can see it, then this is the case. The easiest way to fix the issue is to stop all other (sample) applications and leave only clover.war running on the server. That should guarantee the server will be available in the context root from now on (e.g. http://localhost:9080/).

Figure 3.13. CloverETL Server as the only running application on IBM WebSphere

When using the internal (default) database on Linux, your CloverETL Server might fail on the first start for no obvious reasons. Chances are that the /var/lib/tomcat6/databases directory was not created (because of access rights in parent folders).

Solution: Create the directory yourself and try restarting the server. This simple fix was successfully tested with CloverETL Server deployed as a WAR file via the Tomcat web administration tool.

If the server cannot start and the following message is in the log:

java.sql.SQLException: Failed to start database 'databases/cloverserver'
	  

then see the next exception for details. After that, check settings of the derby.system.home system property. It may point to an unaccessible directory, or files may be locked by another process. We suggest you set a specific directory as the system property.

If you are setting environment variables like clover_license_file or clover_config_file, remember you should not be running more than one CloverETL Server. Therefore, if you ever need to run more instances at once, use other ways of setting parameters (see Part III, “Configuration” for description of all possibilities). The reason is the environment variables are shared by all applications in use causing them to share configurations and fail unexpectedly. Instead of the environment variables, you can use system properties (passed to the application container process using parameter with -D prefix: -Dclover_config_file).

When working with servers, you ought to stick to folder naming rules more than ever. Do not use any special characters in the server path, e.g. spaces, accents, diacritics are not recommended. It's unfortunately common naming strategy on Windows systems. It can produce issues which are hard to find. If you are experiencing weird errors and cannot trace the source of them, install the application server in a safe destination like:

C:\JBoss6\

Similarly, use slashes but never backslashes in paths inside the *.properties files, e.g. when pointing to the CloverETL Server license file. If you incorrectly use backlash, it will be considered an escape character and the server may not work properly. This is an example of a correct path:

license.file=C:/CoverETL/Server/license.dat

Application server must be executed by OS user with proper read/write permissions on file system. Problem may occur, if app-server is executed by root user for the first time, so log and other temp files are created by root user. When the same app-server is executed by another user, it will fail because it cannot write to root's files.

Missing JMS libraries do not cause fail of the server startup, but it is an issue of deployment on an application server, thus it is still related to this chapter.

clover.war itself does not contain jms.jar, so it has to be on an application server's classpath. Most of the application servers have jms.jar by default, but Tomcat, for example, does not. So if the JMS features are needed, the jms.jar has to be added explicitly.

If "JMS Task" feature is used, there must be third-party libraries on a server's classpath as well. The same approach is recommended for JMS Reader/Writer components, even if these components allow to specify external libraries. It is due to common memory leak in these libraries which causes "OutOfMemoryError: PermGen space".

CloverETL Server requires MySQL 5 up to version 5.5 included. Using an unsupported JDBC connector for MySQL might cause an exception, for example:

could not execute query
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 'OPTION SQL_SELECT_LIMIT=DEFAULT' at line 1