[jboss-dev-forums] [Design of Messaging on JBoss (Messaging/JBoss)] - Re: Journal Cleanup and Journal Compactor (Repost)

[clebert.suconic@jboss.com]

Since now I don't need the transaction summary any more (just number of records associated with the transaction at the currentFile), I will be able to move pending transactions. And for doing that I will need to keep all the transaction IDs and everything else.

For doing that, I will need to use temporary files, and rename them as you suggested.


- I will open a journal file with a temporary name. (Open here, means gets it from the cached files, or create a new one).

- As I read the journal files I add the valid records to the temporary file. (I will off course open new files as I fill the file).

- Add a temporary small file when I start renaming the files, and deleting the old files. and delete that file when I'm done.





The only issue I have now is allowing concurrent appends to the journal, as I'm compacting the files.

The problem is, when deleteing or updating a record, I don't know where the AddRecord is going to be located at. So, I don't know where to add the negative value to.

So, what I'm thinking as a solution is:

- During compacting, all Adds, updates and deletes are stored to the current-file, as we aways do.

- But instead of discounting POSFiles right away, I cache those IDs on a collection. When I'm done compacting I do a fast operation applying the reference counts accordingly. 

- Case the server is interrupted during reload, the delete or update will take the original location of the record.


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