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Date: Tue, 30 Nov 2010 20:19:11 -0500 (EST)
From: "Kathey Marsden (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
Subject: [jira] Updated: (DERBY-4917) zero byte dbex.lck file can cause dual
 boot warning saying Severe and non-recoverable corruption can  result and
 may have already occurred.
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     [ https://issues.apache.org/jira/browse/DERBY-4917?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Kathey Marsden updated DERBY-4917:
----------------------------------

    Attachment: ExLockFile.java
                SimpleConnect.java

Here are a couple of small programs for diagnosing the problem that I asked the user to run.,

The first program SimpleConnect, makes a connection to the database and checks the size of the lock file created.
It should be run as 
java SimpleConnect <path to database>
The System.out output should be captured and returned along with the derby.log.
On my system the output is:
$ java SimpleConnect /u/kmarsd/repro/lockwarn/wombat
dbex.lck exists and is length:4
Rename dbex.lck to dbex.lck.sav with f.renameTo
Connection successfully madeorg.apache.derby.impl.jdbc.EmbedConnection30@1023687
94 (XID = 40), (SESSIONID = 0), (DATABASE = /u/kmarsd/repro/lockwarn/wombat), (D
RDAID = null)
length of dbex.lck file:4

I expect on the user  machine the dbex.lck file will be of length 0 which will narrow the problem outside of the applicatoin to just Derby.  If it shows length 4 then something in the application  environment must be influencing  the locking.


Assuming the length shows 0 with SimpleConnect, the second program has just the lock file creation and locking code:

 run like
java ExLockFile <path to db>

The output on my system is:
 java ExLockFile /u/kmarsd/repro/lockwarn/wombat

/u/kmarsd/repro/lockwarn/wombat exists. Attempt exclusive lock
create file succeded. validExclusiveLock=true
1)lockFileOpen = new RandomAccessFile((File) this, "rw")
1) Complete lockFileOpen =java.io.RandomAccessFile@44ba44ba
2) lockFileChannel = lockFileOpen.getChannel()
2) Complete lockFileChannel = sun.nio.ch.FileChannelImpl@51ac51ac
3) dbLock = LockFileChannel.tryLock()
3) Complete dbLock = sun.nio.ch.FileLockImpl[0:9223372036854775807 exclusive val
id]
lockFileOpen.writeInt(EXCLUSIVE_FILE_LOCK)
writeIntSuccessful
lockFileChannel.force(true)
lockChannel.force(true) successful
status = EXCLUSIVE_FILE_LOCK
Lock status is:1-EXCLUSIVE_FILE_LOCK
f.length() = 4

I am thinking maybe at the site we will see an IOException or some sort of other clue.


> zero byte dbex.lck file can cause dual boot warning saying Severe and non-recoverable corruption can  result and may have already occurred.
> -------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: DERBY-4917
>                 URL: https://issues.apache.org/jira/browse/DERBY-4917
>             Project: Derby
>          Issue Type: Bug
>          Components: Store
>    Affects Versions: 10.1.2.1
>         Environment: z/OS 
> E205{S000EKA}> java -version                                            
> java version "1.5.0"                                                    
> Java(TM) 2 Runtime Environment, Standard Edition (build pmz31devifx-    
> 20100215 (SR                                                            
> 11 FP1 ))                                                               
> IBM J9 VM (build 2.3, J2RE 1.5.0 IBM J9 2.3 z/OS s390-31 j9vmmz3123ifx- 
> 20100127a                                                               
>  (JIT enabled)                                                          
> J9VM - 20100122_52103_bHdSMr                                            
> JIT  - 20091016_1845ifx1_r8                                             
> GC   - 20091026_AA)                                                     
> JCL  - 20100215                                                         
> Derby 10.2.2.1 - (815839)
>            Reporter: Kathey Marsden
>         Attachments: ExLockFile.java, SimpleConnect.java
>
>
> User reports the following warning booting Derby 10.2 with JDK 1.5 SR11 FP1 on z/OS.
> ij> connnect 'jdbc:derby:wombat';
> IJ ERROR: Unable to establish connection
> ij> connect 'jdbc:derby:wombat';
> WARNING: Derby (instance c013800d-012c-8027-19b4-000000037b18) is attempting to
> boot the database <snip dbname > even though Derby (instance c0
> 13800d-012c-74ae-07c3-0000000af3f0) may still be active.  Only one instance of D
> erby should boot a database at a time. Severe and non-recoverable corruption can
>  result and may have already occurred.
> The dbex.lck file is zero length.   The code seems to indicate in DirFile4.getExclusiveLock() that a zero length dbex.lck file is possible if the product is booted with less than JDK 1.4 and Derby should show the warning under these circumstances, but investigation shows that even if the dbex,lck file is removed  it is recreated with zero length using JDK 1.5.   So there seem to be two issues.
> 1) dbex.lck is somehow getting created with zero length with JDK 1.5 on this machine with JDK 1.5 SR11 FP1.
> 2)   We have this logic pertaining to JDK 1.3.1 in the product that probably can be removed and perhaps masks a real exclusive locking problem that perhaps should issue an Error rather than a warning if the file cannot be created with 4 bytes as expected.
> I can mimic the Warning on my system with a manufactured zero length  dbex.lck file e.g.
> mv dbex.lck dbex.lck.orig
> touch dbex.lck 
> java org.apache.derby.tools.ij
> ij version 10.2
> ij> connnect 'jdbc:derby:wombat';
> IJ ERROR: Unable to establish connection
> ij> connect 'jdbc:derby:wombat';
> WARNING: Derby (instance c013800d-012c-8027-19b4-000000037b18) is attempting to
> boot the database /u/kmarsd/repro/lockwarn/wombat even though Derby (instance c0
> 13800d-012c-74ae-07c3-0000000af3f0) may still be active.  Only one instance of D
> erby should boot a database at a time. Severe and non-recoverable corruption can
>  result and may have already occurred.
> I see the same warning with 10.7.
> Possible workaround for eliminating the warning is to do a clean shutdown of the derby database before exiting the jvm which will remove the lck files, but it is hard to know if the user is getting actual dual boot protection under these circumstances.
>  

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