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ResourceStore and its saving/flush strategies for writing out configuration to disk

From: Christian Weber <CWeb@DIaLOGIKa.de>
Date: Thu, 28 Jun 2007 11:13:26 +0200
Message-ID: <46837BB6.8030704@DIaLOGIKa.de>
To: <www-jigsaw@w3.org>

Hello all,

i have a question regarding the ResourceStore on how changes to the Jigsaw configuration are saved/flushed to disk.
Assuming the following Scenario:

The Jigsaw server is running and the computer crashes, so that Jigsaw has no time to shutdown anymore.
I'm currently examine this Scenario, because this happens a few days ago, not to me, but i'm used to examine this case 
and shall find out, whether it is possible that Jigsaw has corrupted the files, because it wasn't able to shutdown 
properly, while the computer crashed, or if it's not possible that Jigsaw corrupts the configuration files and isn't 
able to recover from this at the next startup.

After restarting the computer, Jigsaw wasn't able to startup again aborting with this message:
(I replaced the host, path specific entries at the beginning with < >, the rest of the message is untouched )

#loading properties from: <Path to Jigsaw>/Jigsaw/Jigsaw/config/server.props
*** Warning : JigAdmin[2.2.5]: no logger specified, not logging.
JigAdmin[2.2.5]: serving at http://<host>:9444/
FATAL ERROR in element null
Sys  : (internal)
Line : 1
Col  : 0
org.xml.sax.SAXParseException: no document element
         at com.jclark.xml.sax.Driver.parse(Driver.java)
         at org.w3c.tools.resources.serialization.xml.XMLReader.parse(XMLReader.java:226)
         at org.w3c.tools.resources.serialization.xml.XMLReader.readAttributeHolders(XMLReader.java:259)
         at org.w3c.tools.resources.serialization.xml.XMLSerializer.readAttributeHolders(XMLSerializer.java:157)
         at org.w3c.tools.resources.store.ResourceStoreManager.<init>(ResourceStoreManager.java:1442)
         at org.w3c.jigsaw.http.httpd.initializeResourceSpace(httpd.java:752)
         at org.w3c.jigsaw.http.httpd.start(httpd.java:2072)
         at org.w3c.jigsaw.daemon.ServerHandlerManager.<init>(ServerHandlerManager.java:280)
         at org.w3c.jigsaw.daemon.ServerHandlerManager.main(ServerHandlerManager.java:500)
         at org.w3c.jigsaw.Main.main(Main.java:15)
*** salvaging resource manager state...
Unknown error while starting https-server: For input string: "1.tmp"
Exception in thread "main" java.lang.NullPointerException
         at org.w3c.jigsaw.http.httpd.checkpoint(httpd.java:828)
         at org.w3c.jigsaw.http.httpd.shutdown(httpd.java:1516)
         at org.w3c.jigsaw.daemon.ServerHandlerManager.<init>(ServerHandlerManager.java:287)
         at org.w3c.jigsaw.daemon.ServerHandlerManager.main(ServerHandlerManager.java:500)
         at org.w3c.jigsaw.Main.main(Main.java:15)

In order to understand why this happend, it would be great, if you could say, which of the following "Jigsaws saving 
Policies" are correct or if it is handled different.

These strategies comes into my mind:
  - Does Jigsaw loads the configuration, once at the startup, and further doesn't touch the configuration files for
    writing while running, so it only writes the configuration back from memory to disk at shutdown?

  - Or does Jigsaw additionally writes out configuration changes to disk periodically.

  - Does Jigsaw flush changes, made in the AdminGUI, immediately to disk after commiting and saving them or are the
    changes just altered in memory and get written out at shutdown or some periodically save procedure?

Thanks in advance for any help,
Received on Thursday, 28 June 2007 09:13:56 UTC

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