[rules-dev] KnowlegeAgent Tests

[Mark Proctor]

1) the scanner's time doesn't really need to be part of the unit tests, 
as that can be tested separately and we know it'll work. So we can just 
call scan() instead.  See code in 2)

2) I've also moved it to use a CountDownLatch on a afterChangeSetApplied 
event.
     private void scan(KnowledgeAgent kagent) {
         // Calls the Resource Scanner and sets up a listener and a 
latch so we can wait until it's finished processing, instead of using timers
         final CountDownLatch latch = new CountDownLatch( 1 );

         KnowledgeAgentEventListener l = new KnowledgeAgentEventListener() {
             ...

             public void 
afterChangeSetApplied(AfterChangeSetAppliedEvent event) {
                 latch.countDown();
             }
         };

         kagent.addEventListener( l );

         this.scanner.scan();

         try {
             latch.await( 10, TimeUnit.SECONDS );
         } catch ( InterruptedException e ) {
             throw new RuntimeException( "Unable to wait for latch 
countdown", e);
         }

         if ( latch.getCount() > 0 ) {
             throw new RuntimeException( "Event for KnowlegeBase update, 
due to scan, was never received" );
         }

         kagent.removeEventListener( l );
     }

3) All file deletes go through the FileManager. I always do multiple 
attempts at deleting a file and throw an exception if it was not successfuly
     public boolean deleteFile(File file) {
         // This will attempt to delete a file 5 times, calling GC and 
Sleep between each iteration
         // Sometimes windows takes a while to release a lock on a file
         if ( !file.delete() ) {
             int count = 0;
             while ( !file.delete() && count++ < 5 ) {
                 System.gc();
                 try {
                     Thread.sleep( 250 );
                 } catch ( InterruptedException e ) {
                     throw new RuntimeException( "This should never 
happen" );
                 }
             }
         }

         return !file.exists();

     }

3) File writting always waits 1000ms when the file already exists (http 
and linux round to nearest second) so it ensures lastmodified is always 
atleast 1000ms after lastread. See code in 4)

4) All file writting goes via the FileManager where I know attempt to 
write any file 5 times, calling GC and wait between each iteration.
     public void write(File f,
                       String text) throws IOException {
         if ( f.exists() ) {
             // we want to make sure there is a time difference for 
lastModified and lastRead checks as Linux and http often round to seconds
             // 
http://saloon.javaranch.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic&f=1&t=019789
             try {
                 Thread.sleep( 1000 );
             } catch ( Exception e ) {
                 throw new RuntimeException( "Unable to sleep" );
             }
         }

         // Attempt to write the file
         BufferedWriter output = new BufferedWriter( new FileWriter( f ) );
         output.write( text );
         output.close();

         // Now check the file was written and re-attempt if it was not
         // Need to do this for testing, to ensure the texts are read 
the same way, otherwise sometimes you get tail \n sometimes you don't
         String t1 = StringUtils.toString( new StringReader( text ) );

         int count = 0;
         while ( !t1.equals( StringUtils.toString( new BufferedReader( 
new FileReader( f ) ) ) ) && count < 5 ) {
             // The file failed to write, try 5 times, calling GC and 
sleep between each iteration
             // Sometimes windows takes a while to release a lock on a file
             System.gc();
             try {
                 Thread.sleep( 250 );
             } catch ( InterruptedException e ) {
                 throw new RuntimeException( "This should never happen" );
             }
             output = new BufferedWriter( new FileWriter( f ) );
             output.write( text );
             output.close();
             count++;
         }

         if ( count == 5 ) {
             throw new IOException( "Unable to write to file:" + 
f.getCanonicalPath() );
         }
     }

So far between those things the code is now more robust, it's just 
taking time to move it all across :)

We should probably make separate unit tests specifically for 
ResourceScannerImpl, on it's own separate from the rest of hte stack.

Mark
On 04/12/2010 13:26, Esteban Aliverti wrote:
> Mark, let me know if you need some help since this is one of the task 
> in my (almost eternal) TODO list. You can take a look 
> at KnowledgeAgentEventListenerTest.java. Using 
> KnowledgeAgentEventListener, you can be notified when the rule base is 
> recreated and there is no need to wait for x seconds anymore.
> Take a look at the waitUntilChangeSetApplied() method there.
>
> Best,
>
> XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
>
> Esteban Aliverti
> - Developer @ http://www.plugtree.com <http://www.plugtree.com>
> - Blog @ http://ilesteban.wordpress.com
>
>
> On Sat, Dec 4, 2010 at 6:38 AM, Mark Proctor <mproctor at codehaus.org 
> <mailto:mproctor at codehaus.org>> wrote:
>
>     The KnowlegeAgent tests have been fragile for a while, related to
>     "wait"
>     code and file issues, particularly on windows. Something has changed
>     recently and now they aren't working on the linux hudson server
>     either.
>
>     So I'm now in the process of refactoring the tests to make them more
>     robust, and they will hopefully run faster too, as I'll use call backs
>     when something has finished instead of waiting for X seconds in
>     the hope
>     that something has finished.
>
>     Mark
>
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