Troubleshooting

Some things you might want to be aware of:

People working behind firewalls can have problems with the examples which don't run entirely locally. This used to be a problem when Jtrix Ltd ran a public ``hello world'' service, for example (Section ). This is no longer the case, but problems can still occur if you are trying to access other external services.
To see if your firewall is problematic then do two things. First, have a look in hello-warrant.xml and look for some bind servers URL, like this:
```
    ...
    <bind-server>
      <url>http://213.52.152.66:30100/service/2/skeleton</url>;
      <url>http://213.52.152.67:30000/service/2/skeleton</url>;
    </bind-server>
    ...
```
There are two URLs. Next, pick any of these and try to telnet to it. If we pick the first one in the above example (address 213.52.152.66, port 30100) we get this on Linux:
```
% telnet 213.52.152.66 30100
Trying 213.52.152.66...
Connected to 213.52.152.66.
Escape character is '^]'.
```
Everything went well in this example--we connect to the server and get a prompt telling us to hit Control-] to exit. But if your system has problems you will not get this far--it will hang or return some error.
The current solutions are (1) to run such examples from a location without a firewall or with a different firewall, or (2) jump to the other examples which are local only, and do not require external connections. Also, look on http://sourceforge.net/projects/jtrix which will have some discussion on this issue.
Please check you have the latest version of Jtrix. In particular, if you are interacting with a service outside your local environment, then different versions are not guaranteed to be compatible. Jtrix.org will always be running the latest version. This will continue until a 1.0 release, although we will of course try to minimise this as much as possible.
If you are on a dial-up machine and want to run Jtrix on the Internet then make sure you dial-up before you start Jtrix. Otherwise it can timeout before it gets a connection. However, if you just want to run Jtrix locally then this isn't an issue.
Some Linux machines may find problems receiving connections from Hospitality. This can happen if the /etc/hosts file either maps 127.0.0.1 to the machine name, or maps localhost to the machine name. The solution is to change the /etc/hosts file. Lines that begin ``127.0.0.1'' or localhost should have the machine name removed.
To run the Hospitality application you will need a default route. If you are on a Linux machine without networking you may not have one, but you can add a default route going to your local machine (127.0.0.1) with this command:
```
/sbin/route add default gw 127.0.0.1
```
Another option (suitable for both Windows and Linux users) is to amend the jnode script (or jnode.bat on Windows) so that the -shared option is set for that default route.
When running the skeleton application you may find that binding the basic skeleton warrant fails. This may happen if you generate and bind the warrant too quickly; the solution is to wait and try again. The reason is that the skeleton service relies on a worker netlet, and these are not created instantly by the worker pool.
When you shut down and restart an entire node cluster some applications lose their state. One example is SAS. A user's SAS warrant refers to a contract in its database, and this database is (currently) held in memory. So on a restarted cluster the original warrant is found to be invalid and a new one needs to be obtained. On the other hand, the SAS administrator's admin warrant is still valid, and they can use this to reissue the new warrant.
In older versions of Jtrix, we found some Linux systems ran out of threads quite quickly when running two or more nodes on the same machine. The workarounds are either: run Jtrix across different machines; run different nodes as different users; recompile the kernel allowing more threads per user. For this last option look in include/linux/tasks.h and increase NR_TASKS; going to 4000 should be fine. We have not found this a problem on current releases, however.
Some people have got an OutOfMemoryError when running the Webtrix example. This is a silent failure unless you're using the -netlet-stdio option of Jnode. It can result in a ``No Server Found: webtrix-admin'' error in the launcher. The solution is to increase the maximum heap size of the JVM. Use option -Xmx128m on the jnode or jnode.bat command line. This will be given straight to the JVM and will increase its maximum heap size to 128MB.

Nik Silver 2002-03-09