What can I do to prevent write-write conflicts on a wiki-style website?

Question

On a wiki-style website, what can I do to prevent or mitigate write-write conflicts while still allowing the site to run quickly and keeping the site easy to use?

The pr

Answer 1

Your problem (lost update) is solved best using Optimistic Concurrency Control.

One implementation is to add a version column in each editable entity of the system. On user edit you load the row and display the html form on the user. A hidden field gives the version, let's say 3. The update query needs to look something like:

update articles set ..., version=4 where id=14 and version=3;

If rows returned is 0 then someone has already updated article 14. All you need to do then is how to deal with the situation. Some common solutions:

1. last commit wins
2. first commit wins
3. merge conflicting updates
4. let the user decide

Instead of an incrementing version int/long you can use a timestamp but it's not suggested because:

retrieving the current time from the JVM isn't necessarily safe in a clustered environment, where nodes may not be time synchronized.

(quote from Java Persistence with Hibernate)

Some more info at the hibernate documentation.

Answer 2

In Mediawiki, the server accepts the first change, and then when the second edit is saved a conflicts page comes up, and then the second person merges the two changes together. See Wikipedia: Help:Edit Conflicts