Why does django jython connection to a MySQL database give a "Communication Link Failure"?

1
votes

I'm trying to convert a django / cPython app to run as a Tomcat WAR using Jython. We are using a mysql database (MySQLdb in cPython / mysql-connector-java-5.1.15-bin.jar in jython). I have changed the DATABASE_ENGINE between the two configurations. The app runs great with cPython (after I disabled SELinux limitations on http connections to a database). The front page, images, and static content work in the jython. However, when I request a page that hits the database, it seems to hang for a while, then returns with:

Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server. [SQLCode: 0], [SQLState: 08S01]

Has anyone seen this before? I don't see any recent discussions of this type or problem. I'm using django 1.2.5, jython 2.5.2. I've tried running the Java app under Fedora (jre-1.6.0-openjdk.x86_64) and Windows (Java(TM) SE Runtime Environment (build 1.6.0_23-b05)). Same behavior. I've also tried both mysql-connector-java-5.1.15-bin.jar (the latest version) and mysql-connector-java-5.1.10-bin.jar ("extensively tested" according to http://packages.python.org/django-jython/database-backends.html). None of the various configurations affect the behavior.

How can I solve it or where should I look next?

1
pythonmysqldjangotomcatjython
Did you try to play around with SElinux in context of java <-> mysql? - Vasiliy Stavenko
not yet, but I haven't seen any messages to suggest that it's denying anything. I'll try completely disabling it just to test. - Carl F.

1 Answers

0
votes

I found the mistake. In hindsight, it's obvious. I made a type-o in the IP address of the database server, but only in the configuration file on the jython branch. As a result, the Jython instance hung while the cPython instance didn't. Found the error when I merged the two into a single settings.py (using "if os.name=='java'" to make the necessary jython changes.

So . . . What's the correct protocol here? Should I delete the question or leave it up in case someone else makes the same type of mistake I did?