id,summary,reporter,owner,description,type,status,priority,milestone,component,version,resolution,keywords,cc,launchpad_bug 254,need better user output on UncoordinatedWriteError,zooko,zooko,"The current strategy for solving [http://allmydata.org/trac/tahoe/browser/docs/mutable.txt?rev=955bd5383daed77c#L29 the eternal puzzle of availability vs. consistency] in the presence of multiple uncoordinated writes is to tell the user ""Don't Do That."" -- don't allow multiple people, or multiple processes belonging to the same person, to write to the same directory at the same time. (For example, make a different directory for each person who needs to write.) This strategy has many benefits, including being easy to implement, easy to understand, offering perfect availability, and being flexible for many different use cases. However, it has the drawback that so far no actual user has read the doc (source:doc/mutable.txt) and planned in advance to avoid uncoordinated writes. In fact, even I, one of the architects of the ""Don't Do That."" strategy, have often forgotten, and Done It. This shows that for some but not all of those aforementioned many use cases, people are going to want a more automated way to trade away some availability in order to get consistency. This automation might not need to live in Tahoe proper, but might be more of a feature of the user interface or application layer. Anyway, the very next improvement, which we should do ASAP, is make the error message that arises clearly explain to the user that (a) this is the expected result of uncoordinated writes, not an internal error in the Tahoe implementation, and (b) who wrote what when (inasmuch as we can easily provide clues about that), and (c) ""Don't Do That!"".",defect,closed,major,0.9.0 (Allmydata 3.0 final),documentation,0.7.0,wontfix,consistency availability uncoordinated-writes,warner secorp,