Modification on an entry should always be flushed to the disk

• Key: DIRSERVER-685
• Type: New Feature
• Status: Closed
• Resolution: Fixed
• Priority: Critical
• Assignee: Alex Karasulu
• Reporter: Emmanuel Lecharny
• Fix Version/s: 1.5.0, 1.0-RC4

Description

When modifying an entry, we should always flush this entry to the disk.

The JDBM backend, AFAIK, only update its cache, and a thread flush those caches periodicaly. However, I may be wrong (and I hope to be wrong :)

Comments

[Emmanuel Lecharny]

In fact, there is an existing flag (synchOnWrite) which has been created to implement this behavious, but it's always set to false, so we never have synchornization on write.

This flag should be set to true by default, and the server.xml configuration may contains a way to modify this value to false (even if this seems obviously dangerous to do so ...)

[Jörg Henne]

Great to see you have a look at this problem. I've noticed that upon unclean shutdowns, updates are usually lost. A quick glance at the code indicated that the JDBM commit was only called during clean shutdown, so this issue was already on my list. Since even if there are not formal transactions, DS should try to ensure durability of updates. This means committing after each update by default, despite the performance hit it will bring about.

[Alex Karasulu]

Sync on write is now the default mechanism without the buffer cache. We should have all write based operations pushed directly to disk.